[Senate Hearing 112-532]
[From the U.S. Government Printing Office]








                                                        S. Hrg. 112-532

              INDUCED SEISMICITY FROM ENERGY TECHNOLOGIES

=======================================================================

                                HEARING

                               before the

                              COMMITTEE ON
                      ENERGY AND NATURAL RESOURCES
                          UNITED STATES SENATE

                      ONE HUNDRED TWELFTH CONGRESS

                             SECOND SESSION

                                   TO

 RECEIVE TESTIMONY ON THE POTENTIAL FOR INDUCED SEISMICITY FROM ENERGY 
TECHNOLOIGES, INCLUDING CARBON CAPTURE AND STORAGE, ENHANCED GEOTHERMAL 
     SYSTEMS, PRODUCTION FROM GAS SHALES, AND ENHANCED OIL RECOVERY

                               __________

                             JUNE 19, 2012










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               COMMITTEE ON ENERGY AND NATURAL RESOURCES

                  JEFF BINGAMAN, New Mexico, Chairman

RON WYDEN, Oregon                    LISA MURKOWSKI, Alaska
TIM JOHNSON, South Dakota            JOHN BARRASSO, Wyoming
MARY L. LANDRIEU, Louisiana          JAMES E. RISCH, Idaho
MARIA CANTWELL, Washington           MIKE LEE, Utah
BERNARD SANDERS, Vermont             RAND PAUL, Kentucky
DEBBIE STABENOW, Michigan            DANIEL COATS, Indiana
MARK UDALL, Colorado                 ROB PORTMAN, Ohio
JEANNE SHAHEEN, New Hampshire        JOHN HOEVEN, North Dakota
AL FRANKEN, Minnesota                DEAN HELLER, Nevada
JOE MANCHIN, III, West Virginia      BOB CORKER, Tennessee
CHRISTOPHER A. COONS, Delaware

                    Robert M. Simon, Staff Director
                      Sam E. Fowler, Chief Counsel
               McKie Campbell, Republican Staff Director
               Karen K. Billups, Republican Chief Counsel













                            C O N T E N T S

                              ----------                              

                               STATEMENTS

                                                                   Page

Bingaman, Hon. Jeff, U.S. Senator From New Mexico................     1
Hitzman, Murray W., Charles Fogarty, Professor of Economic 
  Geology, Department of Geology and Geological Engineering, 
  Colorado School of Mines, Golden, CO...........................     3
Leith, William, Senior Science Advisor for Earthquake and 
  Geologic Hazards, U.S. Geological Survey Department of the 
  Interior.......................................................    10
Murkowski, Hon. Lisa, U.S. Senator From Alaska...................     2
Petty, Susan, President and Chief Technology Officer, Alta Rock 
  Energy, Inc, Seattle, WA.......................................    15
Zoback, Mark D., Benjamin M. Page Professor of Earth Sciences, 
  Department of Geophysics, Stanford University, Stanford, CA....    33

                                APPENDIX

Responses to additional questions................................    49

 
              INDUCED SEISMICITY FROM ENERGY TECHNOLOGIES

                              ----------                              


                         TUESDAY, JUNE 19, 2012

                               U.S. Senate,
                 Committee on Energy and Natural Resources,
                                                    Washington, DC.
    The committee met, pursuant to notice, at 10:03 a.m. in 
room SD-366, Dirksen Senate Office Building, Hon. Jeff 
Bingaman, chairman, presiding.

OPENING STATEMENT OF HON. JEFF BINGAMAN, U.S. SENATOR FROM NEW 
                             MEXICO

    The Chairman. OK. Why don't we get started? Senator 
Murkowski is delayed a very few minutes here, but asked us to 
go ahead and proceed.
    Welcome everyone to the hearing. This is on the potential 
for inducing manmade earthquakes from energy technologies. Many 
of the current and next generation energy technologies that are 
vital to our country's future require the injection of fluids 
like water and carbon dioxide or other mixtures deep into the 
Earth's subsurface.
    Geothermal energy extraction, geological carbon 
sequestration, the injection of waste water from hydraulic 
fracturing and enhanced oil recovery all require the injection 
and movement of fluids deep underground. Scientists have known 
for many decades that one potential side effect of pumping 
fluids in or out of the Earth is the creation of small to 
medium sized earthquakes. Though only a small number of recent 
seismic events here and abroad have been definitely linked to 
energy development, public concern has been raised about the 
potential for manmade earthquakes after seismic events that 
were felt in Arkansas and Oklahoma and Ohio and other places in 
the country. Those events in some cases were located near 
energy development and waste disposal sites.
    In 2010 I asked Secretary Chu to initiate a comprehensive 
and independent study by the National Academy of Sciences and 
the National Academy of Engineering to examine the possible 
scale, scope and consequences of seismicity induced by energy 
technologies. In particular, I asked them to focus on the 
potential for induced seismicity from enhanced geothermal 
systems, production from gas shales, enhanced oil recovery and 
carbon capture and storage.
    The Academy released their report this past Friday. The 
results provide a timely assessment of the potential hazards 
and risks of induced seismicity potential posed by these energy 
technologies. I want to thank the members of the Study 
Committee, the staff of the National Academies and all of those 
associated with putting together this important report for 
their very hard work.
    The National Academy of Science's Committee found that of 
all the energy related injection and extraction activities 
conducted in the United States only a small percentage have 
created earthquakes at levels noticeable to humans. None have 
caused significant damage to life or property.
    The committee also determined that because hydraulic 
fracturing for natural gas development typically involves the 
injection of relatively small amounts of fluid into localized 
areas. Hydraulic fracturing, itself, rarely triggers 
earthquakes large enough to be felt. Activities that inject 
greater amounts of fluid over longer periods of time, however, 
such as the injection of drilling waste water, pose a greater 
risk for causing noticeable earthquakes.
    Recent data from USGS suggests that the rate of earthquakes 
in the U.S. mid-continent has increased significantly in the 
past decade. The locations of these earthquakes are near many 
oil and gas extraction operations. As a result have raised 
public concern that they are the result of underground 
injection of drilling waste water.
    The study also indicates that injection and storing--
injecting and storing vast amounts of carbon dioxide in the 
subsurface may pose a risk for seismicity that needs to be 
better understood and quantified through research.
    The discussion we're having today is an important and 
timely one. As the National Academy's report indicates risk 
from manmade earthquakes associated with energy technologies 
has been minimal and provided appropriate proactive measures 
are taken, may be effectively managed for the future. I look 
forward to hearing more about the topic from our panel of 
expert witnesses here.
    Let me defer to Senator Murkowski for any comments she has 
before I introduce the witnesses.

        STATEMENT OF HON. LISA MURKOWSKI, U.S. SENATOR 
                          FROM ALASKA

    Senator Murkowski. Thank you, Mr. Chairman and good morning 
to all of our witnesses today. I do look forward to your 
testimony also.
    Over the past year or so I think we've all seen some of the 
trade press articles about issues of induced seismicity. While 
some of the headlines might look a bit sensational, it did seem 
that the true risk in reality is actually quite remote. But as 
such it's good to get a reality check from the experts. That's 
why you have been invited here today.
    The headline on this study from the NAS reads, ``Federal 
Research concludes quake risk from drilling low, avoidable.'' 
This covers geothermal wells, oil and gas wells and waste water 
wells. Really the unfortunate thing here is that the headline 
associates this report with drilling when drilling is perhaps 
not the issue so much as the actual permanent injection of 
waste water or carbon into an area where the pressures have 
become destabilized and some vibration then occurs.
    I think it's good news that most of the seismic activity 
under discussion here, even with the hundreds of thousands of 
areas energy projects at play, have been quite small and often 
barely noticeable to humans. None of this is to say that anyone 
should be dismissive of this discussion. I think we all know 
that energy development of all sources and in all places does 
have attendant risks and impacts. It's not surprising to me to 
see that injecting and removing large volumes of fluids and 
gases underground might, under some conditions, cause 
vibrations to be felt above the ground. The question is whether 
that sort of seismicity is avoidable and manageable.
    The study that we're looking at seems to indicate the 
answer is yes, which is also not surprising. But I'm interested 
to hear our other witnesses? views on the study. Since the 
study was only released on Friday, I realize that you may have 
more to say once you've had more time to actually study it 
carefully. But I do look forward to your initial impressions 
today.
    With that, I thank the Chairman.
    The Chairman. Thank you very much.
    Let me introduce our witnesses.
    First will be Dr. Murray Hitzman, who is a Professor with 
Colorado School of Mines. He's also Chairman of the National 
Academy's Committee that has prepared this report. So we thank 
you again for that heroic effort.
    Dr. William Leith is the Senior Science Advisor for 
Earthquake and Geologic Hazards with the Geological Survey.
    Ms. Susan Petty is President and Chief Technology Officer 
with Altarock Energy. Thank you very much for being here.
    Dr. Mark Zoback is a Professor at Stanford. He's testified 
here before and we welcome him back.
    Dr. Hitzman, why don't you go right ahead?
    If each of you could take 5 or 6 minutes and tell us the 
main points you think we need to try to understand. Then we 
will undoubtedly have questions.

 STATEMENT OF MURRAY W. HITZMAN, CHARLES FOGARTY PROFESSOR OF 
    ECONOMIC GEOLOGY, DEPARTMENT OF GEOLOGY AND GEOLOGICAL 
       ENGINEERING, COLORADO SCHOOL OF MINES, GOLDEN, CO

    Mr. Hitzman. Thank you very much.
    Chairman Bingaman, Ranking Member Murkowski and members of 
the committee, thank you for the invitation to address you.
    Although the vast majority of earthquakes that occur in the 
world each year have natural causes, some of these earthquakes 
and a number of lesser magnitude seismic events are related to 
human activities and are called induced seismic events or 
induced earthquakes. Since the 1920s we have recognized that 
pumping fluids into or out of the Earth has the potential to 
cause seismic imbalance that can be felt. Only a very small 
fraction of injection and extraction activities at hundreds of 
thousands of energy development sites in the U.S. have induced 
seismicity at levels that are noticeable to the public.
    However, seismic events caused by or likely related to 
energy developments have been measured and felt in a number of 
States. Although none of these events has resulted in loss of 
life or significant structural damage, their effects were felt 
by local residents, some of whom also experienced minor 
property damage. Anticipating public concern about the 
potential for induced seismicity related to energy development, 
Chairman, Senator Bingaman, did request from DOE that they 
conduct a study of this issue through the National Research 
Council.
    The committee that wrote the NRC report released last 
Friday consisted of 11 experts in various aspects of seismicity 
and energy technologies from both academia and industry.
    The committee found that induced seismicity associated with 
fluid injection or withdrawal associated with energy 
development is caused, in most cases, by a change in pore 
pressure and/or change in stress in the subsurface in the 
presence of faults with specific properties and orientations 
and a critical state of stress in the rocks. The factor that 
appears to have the most direct consequence in regard to 
induced seismicity is the net fluid balance or put more simply, 
the total balance of fluid either introduced or taken out from 
the subsurface. Additional factors may also influence the way 
fluids affect the subsurface.
    The committee concluded that while the general mechanisms 
that create induced seismic events are well understood. We are 
currently unable to accurately predict the magnitude or 
occurrence of such events due to the lack of a comprehensive 
data on complex natural rocks or systems in the subsurface and 
the lack of validated predictive models.
    The committee found for the largest induced seismic events 
associated with energy projects were those that did not balance 
the large volumes of fluids injected into or extracted from the 
Earth. We emphasize this is a statistical observation. It 
suggests, however, that the net volume of fluid that is 
injected and/or extracted may serve as a proxy for the changes 
in subsurface stress conditions in pore pressure.
    I'm going to briefly discuss the induced seismicity 
potential now for each of the energy technologies that was 
asked for in the report.
    Although it felt induced seismicity has been documented 
with the development of geothermal resources, such development 
usually attempts to keep a mass balance between fluid volumes 
produced and fluids replaced by injection to extend the 
longevity of the energy resource. This fluid balance helps to 
maintain fairly constant reservoir pressure, close to the 
initial preproduction value and aids in reducing the potential 
for induced seismicity.
    Oil and gas extraction from a reservoir may cause induced 
seismic events. These events are rare, relative to the large 
number of oil and gas fields around the world and appear to be 
related to decrease in pore pressure as fluid has been drawn.
    Secondary recovery and enhanced oil recoveries or EOR for 
oil and gas production both involve injection of fluids into 
the subsurface to push more of the hydrocarbons out of the pore 
spaces and to maintain reservoir pressure. Approximately 
151,000 injection wells are currently permitted in the U.S.
    For a combination of secondary recovery EOR and waste water 
disposal with only a very few documented incidents where the 
injection caused or is likely related to felt seismic events.
    Among the tens of thousands of wells used for enhanced oil 
recovery in the U.S. the committee did not find any 
documentation in the published literature of felt induced 
seismicity.
    Shale formations also contain hydrocarbons. The extremely 
low permeability of these rocks has trapped the hydrocarbons 
and prevented them from migrating from the rock. The low 
permeability also prevents the hydrocarbons from easily flowing 
into a well bore without production stimulation.
    These types of unconventional reservoirs are developed by 
drilling rails horizontally through the reservoir rock and 
using hydraulic fracturing techniques to create new fractures 
in the reservoir to allow us to get the hydrocarbons out. About 
35,000 hydraulically fractured shale wells exist in the U.S. 
Only one case of felt seismicity in the United States has been 
described in which hydraulic fracturing for shale gas 
development is suspected but not confirmed. Globally, one case 
of felt induced seismicity in Blackpool, England has been 
confirmed as being caused by hydraulic fracturing for shale gas 
development.
    The very low number of felt events relative to the large 
number of hydraulically fractured wells for shale gas is likely 
due to the short duration of injection of fluids and the 
limited fluid volumes used.
    In addition to the fluid injection directly related to 
energy development, injection wells drilled to dispose of waste 
water generated during oil and gas production are very common 
in the United States. Tens of thousands of waste water disposal 
wells are currently active. Although only a few induced seismic 
events have been linked to these disposal wells, the occurrence 
of these events has generated considerable public concern.
    Examination of these cases suggest casual links between the 
injection zones and previously unrecognized faults in the 
subsurface. Injection wells are used only for the purpose of 
waste water disposal normally do not have a detailed geologic 
review performed prior to injection and the data are often not 
available to make such a detailed review. Thus the location of 
the possible nearby faults is often not a standard part of 
citing and drilling these disposal wells. In addition, the 
presence of a fault does not necessarily imply an increased 
potential for induced seismicity.
    The majority of hazardous and non-hazardous waste water 
disposal wells do not pose a hazard for induced seismicity. 
However, the long term affects of any significant increases in 
the number of waste water disposal wells in a particular area 
on induced seismicity are unknown.
    Carbon capture and sequestration or CCS is also a means of 
disposing of fluids in the subsurface. The committee found that 
the risk of induced seismicity from CCS is currently difficult 
to accurately assess. With only a few small scale commercial 
projects overseas and several small demonstration projects 
underway in the U.S., there are few data available to evaluate 
the induced seismicity potential of this technology.
    The existing projects have involved relatively small 
injection volumes. CCS differs from the other energy 
technologies in that it involves continuous injection of carbon 
dioxide fluid at high rates, under pressure, for long periods 
of time. It is purposely intended for permanent storage. 
There's no fluid withdrawal.
    Given that the potential magnitude from induced seismic 
event correlates strongly with a fault rupture area. Which in 
turn relates to the magnitude of pore pressure change and the 
rock volume which exists, the committee determined that large 
scale CCS may have the potential for causing significant 
induced seismicity.
    The committee also investigated governmental responses to 
induced seismic events. Responses have been undertaken by a 
number of Federal and State agencies in a variety of ways. To 
date, Federal and State agencies have dealt with induced 
seismic events with different and localized actions.
    These actions have been successful, but they've been ad hoc 
in nature. With the potential for increased numbers of induced 
seismic events due to expanding energy development governmental 
agencies and research institutions may not have sufficient 
resources to address unexpected events. The committee concluded 
that forward looking, interagency cooperation to address 
potential induced seismicity is warranted.
    Methodologies can be developed for quantitative 
probabilistic hazard assessments of induced seismicity risk. 
The committee determined that such assessments should be 
undertaken before operations begin in areas with a known 
history of felt seismicity and updated in response to observed, 
potentially induced events. The committee suggested that 
practices that consider induced seismicity both before and 
during the actual operations of an energy project should be 
employed to develop best practices protocols specific to each 
of the energy technologies and to site location.
    Although induced seismic events have not resulted in loss 
of life or major damage to the U.S., their effects have been 
felt locally and they raise some concern about additional 
seismic activity and its consequences in areas where energy 
development is ongoing or planned. Further research is required 
to better understand and address the potential risks associated 
with induced seismicity.
    I'd like to thank the committee for its time and its 
interest in this subject. I request the balance of my written 
testimony be placed in the record. I certainly look forward to 
your questions.
    [The prepared statement of Mr. Hitzman follows:]

 Prepared Statement of Murray W. Hitzman, Charles Fogarty Professor of 
  Economic Geology, Department of Geology and Geological Engineering, 
                  Colorado School of Mines, Golden, CO
    Chairman Bingaman, Ranking Member Murkowski, and members of the 
committee, I would like to thank you for the invitation to address you 
on the subject of induced seismicity potential in energy technologies. 
My name is Murray Hitzman. I am a professor of geology at the Colorado 
School of Mines in Golden, Colorado and served as the chair of the 
National Research Council Committee on Induced Seismicity Potential in 
Energy Technologies. The Research Council is the operating arm of the 
National Academy of Sciences, National Academy of Engineering, and the 
Institute of Medicine of the National Academies, chartered by Congress 
in 1863 to advise the government on matters of science and technology. 
I would like to thank the committee for the invitation to address it on 
the subject of induced seismicity potential in energy technologies.
    Although the vast majority of earthquakes that occur in the world 
each year have natural causes, some of these earthquakes and a number 
of lesser magnitude seismic events are related to human activities and 
are called ``induced seismic events'' or ``induced earthquakes.''
    Induced seismic activity has been attributed to a range of human 
activities including the impoundment of large reservoirs behind dams, 
controlled explosions related to mining or construction, and 
underground nuclear tests. Energy technologies that involve injection 
or withdrawal of fluids from the subsurface can also create induced 
seismic events that can be measured and felt.
    Since the 1920s we have recognized that pumping fluids into or out 
of the Earth has the potential to cause seismic events that can be 
felt. Only a very small fraction of injection and extraction activities 
at hundreds of thousands of energy development sites in the United 
States have induced seismicity at levels that are noticeable to the 
public. However, seismic events caused by or likely related to energy 
development have been measured and felt in Alabama, Arkansas, 
California, Colorado, Illinois, Louisiana, Mississippi, Nebraska, 
Nevada, New Mexico, Ohio, Oklahoma, and Texas. Although none of these 
events resulted in loss of life or significant structural damage, their 
effects were felt by local residents, some of whom also experienced 
minor property damage. Particularly in areas where natural seismic 
activity is uncommon and energy development is ongoing, these induced 
seismic events, though small in scale, can be disturbing to the public 
and raise concern about increased seismic activity and its potential 
consequences.
    Anticipating public concern about the potential for induced 
seismicity related to energy development, the Chairman of this 
Committee, Senator Bingaman, requested that the Department of Energy 
conduct a study of this issue through the National Research Council. 
The Chairman requested that this study examine the scale, scope, and 
consequences of seismicity induced during the injection of fluids 
related to energy production. The energy technologies to be considered 
included geothermal energy development, oil and gas production, 
including enhanced oil recovery and shale gas, and carbon capture and 
storage or CCS. The study was also to identify gaps in knowledge and 
research needed to advance the understanding of induced seismicity; to 
identify gaps in induced seismic hazard assessment methodologies and 
the research needed to close those gaps; and to assess options for 
interim steps toward best practices with regard to energy development 
and induced seismicity potential. The National Research Council (NRC) 
released the report Induced Seismicity Potential in Energy Technologies 
on June 15.
    The committee that wrote this NRC report consisted of eleven 
experts in various aspects of seismicity and energy technologies from 
academia and industry. The committee examined peer-reviewed literature, 
documents produced by federal and state agencies, online databases and 
resources, and information requested from and submitted by external 
sources. We heard from government and industry representatives. We also 
talked with members of the public familiar with the world's largest 
geothermal operation at The Geysers at a public meeting in Berkeley, 
California. We also spoke to people familiar with shale gas 
development, enhanced oil recovery, waste water disposal from energy 
development, and CCS at meetings in Dallas, Texas and Irvine, 
California. Meetings were also held in Washington, D.C. and Denver, 
Colorado to explore induced seismicity in theory and in practice.
    This study took place during a period in which a number of small, 
felt seismic events occurred that were likely related to fluid 
injection for energy development. Because of their recent occurrence, 
peer-reviewed publications about most of these events were generally 
not available. However, knowing that these events and information about 
them would be anticipated in this report, the committee attempted to 
identify and seek information from as many sources as possible to gain 
a sense of the common factual points involved in each instance, as well 
as the remaining, unanswered questions about these cases. Through this 
process, the committee has engaged scientists and engineers from 
academia, industry, and government because each has credible 
information to add to better understanding of induced seismicity.
    The committee found that induced seismicity associated with fluid 
injection or withdrawal associated with energy development is caused in 
most cases by change in pore fluid pressure and/or change in stress in 
the subsurface in the presence of faults with specific properties and 
orientations and a critical state of stress in the rocks. The factor 
that appears to have the most direct consequence in regard to induced 
seismicity is the net fluid balance or put more simply, the total 
balance of fluid introduced into or removed from the subsurface. 
Additional factors may also influence the way fluids affect the 
subsurface. The committee concluded that while the general mechanisms 
that create induced seismic events are well understood, we are 
currently unable to accurately predict the magnitude or occurrence of 
such events due to the lack of comprehensive data on complex natural 
rock systems and the lack of validated predictive models.
    The committee found that the largest induced seismic events 
associated with energy projects reported in the technical literature 
are associated with projects that did not balance the large volumes of 
fluids injected into, or extracted from, the Earth. We emphasize that 
this is a statistical observation. It suggests, however, that the net 
volume of fluid that is injected and/or extracted may serve as a proxy 
for changes in subsurface stress conditions and pore pressure. The 
committee recognizes that coupled thermo-mechanical and chemo-
mechanical effects may also play a role in changing subsurface stress 
conditions.
    I will briefly discuss the potential for induced seismicity with 
each of the energy technologies that the committee considered, 
beginning with geothermal energy.
Geothermal Energy
    The three different types of geothermal energy resources are: (1) 
``vapor-dominated'', where primarily steam is contained in the pores or 
fractures of hot rock, (2) ``liquid-dominated'', where primarily hot 
water is contained in the rock, and (3) ``Enhanced Geothermal Systems'' 
(EGS), where the resource is hot, dry rock that requires engineered 
stimulation to allow fluid movement for commercial development. 
Although felt induced seismicity has been documented with all three 
types of geothermal resources, geothermal development usually attempts 
to keep a mass balance between fluid volumes produced and fluids 
replaced by injection to extend the longevity of the energy resource. 
This fluid balance helps to maintain fairly constant reservoir 
pressure-close to the initial, pre-production value-and aids in 
reducing the potential for induced seismicity.
    Seismic monitoring at liquid-dominated geothermal fields in the 
western United States has demonstrated relatively few occurrences of 
felt induced seismicity. However, in vapor or steam dominated 
geothermal system at The Geysers in northern California, the large 
temperature difference between the injected fluid and the geothermal 
reservoir results in significant cooling of the hot subsurface 
reservoir rocks. This has resulted in a significant amount of observed 
induced seismicity. EGS technology is in the early stages of 
development. Many countries including the United States have pilot 
projects to test the potential for commercial production. In each case 
of active EGS development, at least some, generally minor levels of 
felt induced seismicity have been recorded.
Conventional Oil & Gas
    Oil and gas extraction from a reservoir may cause induced seismic 
events. These events are rare relative to the large number of oil and 
gas fields around the world and appear to be related to decrease in 
pore pressure as fluid is withdrawn.
    Oil or gas reservoirs often reach a point when insufficient 
pressure exists to allow sufficient hydrocarbon recovery. Various 
technologies, including secondary recovery and tertiary recovery--also 
called enhanced oil recovery or EOR--can be used to extract some of the 
remaining oil and gas. Secondary recovery and EOR technologies both 
involve injection of fluids into the subsurface to push more of the 
trapped hydrocarbons out of the pore spaces in the reservoir and to 
maintain reservoir pore pressure. Secondary recovery often uses water 
injection or ``waterflooding'' and EOR technologies often inject carbon 
dioxide. Approximately 151,000 injection wells are currently permitted 
in the United States for a combination secondary recovery, EOR, and 
waste water disposal with only very few documented incidents where the 
injection caused or was likely related to felt seismic events. 
Secondary recovery-through waterflooding-has been associated with very 
few felt induced seismic events. Among the tens of thousands of wells 
used for EOR in the United States, the committee did not find any 
documentation in the published literature of felt induced seismicity.
Shale Gas
    Shale formations can also contain hydrocarbons-gas and/or oil. The 
extremely low permeability of these rocks has trapped the hydrocarbons 
and largely prevented them from migrating out of the rock. The low 
permeability also prevents the hydrocarbons from easily flowing into a 
well bore without production stimulation by the operator. These types 
of ``unconventional'' reservoirs are developed by drilling wells 
horizontally through the reservoir rock and using hydraulic fracturing 
techniques to create new fractures in the reservoir to allow the 
hydrocarbons to migrate up the well bore. This process is now commonly 
referred to as ``fracking.'' About 35,000 hydraulically fractured shale 
gas wells exist in the United States. Only one case of felt seismicity 
in the United States has been described in which hydraulic fracturing 
for shale gas development is suspected, but not confirmed. Globally 
only one case of felt induced seismicity at Blackpool, England has been 
confirmed as being caused by hydraulic fracturing for shale gas 
development. The very low number of felt events relative to the large 
number of hydraulically fractured wells for shale gas is likely due to 
the short duration of injection of fluids and the limited fluid volumes 
used in a small spatial area.
Waste Water Disposal
    In addition to fluid injection directly related to energy 
development, injection wells drilled to dispose of waste water 
generated during oil and gas production, including during hydraulic 
fracturing, are very common in the United States. Tens of thousands of 
waste water disposal wells are currently active throughout the country. 
Although only a few induced seismic events have been linked to these 
disposal wells, the occurrence of these events has generated 
considerable public concern. Examination of these cases suggests causal 
links between the injection zones and previously unrecognized faults in 
the subsurface.
    In contrast to wells for EOR which are sited and drilled for 
precise injection into well-characterized oil and gas reservoirs, 
injection wells used only for the purpose of waste water disposal 
normally do not have a detailed geologic review performed prior to 
injection and the data are often not available to make such a detailed 
review. Thus, the location of possible nearby faults is often not a 
standard part of siting and drilling these disposal wells. In addition, 
the presence of a fault does not necessarily imply an increased 
potential for induced seismicity. This creates challenges for the 
evaluation of potential sites for disposal injection wells that will 
minimize the possibility for induced seismic activity.
    Most waste water disposal wells typically involve injection at 
relatively low pressures into large porous aquifers that have high 
natural permeability, and are specifically targeted to accommodate 
large volumes of fluid. Of the well-documented cases of induced 
seismicity related to waste water fluid injection, many are associated 
with operations involving large amounts of fluid injection over 
significant periods of time. Thus, although a few occurrences of 
induced seismic activity associated with waste water injection have 
been documented, the majority of the hazardous and nonhazardous waste 
water disposal wells do not pose a hazard for induced seismicity. 
However, the long-term effects of any significant increases in the 
number of waste water disposal wells in particular areas on induced 
seismicity are unknown.
Carbon capture and sequestration
    Carbon capture and sequestration--or CCS--is also a means of 
disposing of fluid in the subsurface. The committee found that the risk 
of induced seismicity from CCS is currently difficult to accurately 
assess. With only a few small-scale commercial projects overseas and 
several small-scale demonstration projects underway in the United 
States, there are few data available to evaluate the induced seismicity 
potential of this technology. The existing projects have involved very 
small injection volumes. CCS differs from other energy technologies in 
that it involves continuous injection of carbon dioxide fluid at high 
rates under pressure for long periods of time. It is purposely intended 
for permanent storage--meaning that there is no fluid withdrawal. Given 
that the potential magnitude of an induced seismic event correlates 
strongly with the fault rupture area, which in turn relates to the 
magnitude of pore pressure change and the rock volume in which it 
exists, the committee determined that large-scale CCS may have the 
potential for causing significant induced seismicity.
    The committee's findings suggest that energy projects with large 
net volumes of injected or extracted fluids over long periods of time, 
such as long-term waste water disposal wells and CCS, appear to have a 
higher potential for larger induced seismic events. The magnitude and 
intensity of possible induced events would be dependent upon the 
physical conditions in the subsurface-state of stress in the rocks, 
presence of existing faults, fault properties, and pore pressure.
    The committee also investigated governmental responses to induced 
seismic events. Responses have been undertaken by a number of federal 
and state agencies in a variety of ways. Four federal agencies-the 
Environmental Protection Agency (EPA) the Bureau of Land Management 
(BLM), the U.S. Department of Agriculture Forest Service (USFS), and 
the U.S. Geological Survey (USGS)-and different state agencies have 
regulatory oversight, research roles and/or responsibilities related to 
different aspects of the underground injection activities that are 
associated with energy technologies. Currently EPA has primary 
regulatory responsibility for fluid injection under the Safe Drinking 
Water Act. It is important to note that the Safe Drinking Water Act 
does not explicitly address induced seismicity.
    To date, federal and state agencies have dealt with induced seismic 
events with different and localized actions. These actions have been 
successful but have been ad hoc in nature. With the potential for 
increased numbers of induced seismic events due to expanding energy 
development, government agencies and research institutions may not have 
sufficient resources to address unexpected events. The committee 
concluded that forward-looking interagency cooperation to address 
potential induced seismicity is warranted.
    Methodologies can be developed for quantitative, probabilistic 
hazard assessments of induced seismicity risk. The committee determined 
that such assessments should be undertaken before operations begin in 
areas with a known history of felt seismicity and updated in response 
to observed, potentially induced seismicity. The committee suggested 
that practices that consider induced seismicity both before and during 
the actual operation of an energy project should be employed to develop 
a ``best practices'' protocol specific to each energy technology and 
site location. The committee's meetings with individuals from Anderson 
Springs and Cobb, California, who live with induced seismicity 
continuously generated by geothermal energy production at The Geysers 
were invaluable in understanding how such a best practices protocol 
works.
    Although induced seismic events have not resulted in loss of life 
or major damage in the United States, their effects have been felt 
locally, and they raise some concern about additional seismic activity 
and its consequences in areas where energy development is ongoing or 
planned. Further research is required to better understand and address 
the potential risks associated with induced seismicity.
    I would like to thank the committee for its time and interest in 
this subject and I look forward to questions.

    The Chairman. Thank you very much.
    Dr. Leith, go right ahead.

    STATEMENT OF WILLIAM LEITH, SENIOR SCIENCE ADVISOR FOR 
   EARTHQUAKE AND GEOLOGIC HAZARDS, U.S. GEOLOGICAL SURVEY, 
                   DEPARTMENT OF THE INTERIOR

    Mr. Leith. Mr. Chairman, members of the committee, thank 
you for inviting the USGS to testify at this hearing.
    The United States is expanding its use of technologies that 
involve the injection and production of fluid at depth. As 
detailed in the report released last week by the National 
Research Council, the practices employed in these technologies 
have the potential to induce earthquakes. I commend this 
committee for requesting that such a study be undertaken and 
the Department of Energy for commissioning and funding the 
study. The NRC panel has done an outstanding job and made a 
significant contribution on this important issue.
    Since 2011 the central and eastern portions of the U.S. 
have experienced a number of moderately strong earthquakes in 
areas of historically low seismicity. Of these, only the 
earthquake that occurred last August in Central Virginia is 
unequivocally a natural tectonic earthquake. In all of the 
other cases there arises the possibility that the earthquakes 
were induced by waste water disposal.
    The disposal of fluids by deep injection is occurring more 
frequently in recent years. The occurrence of induced 
seismicity associated with fluid disposal from natural gas 
production in particular has increased significantly since the 
expanded use of hydraulic fracturing. Although there appears to 
be very little hazard associated with hydraulic fracturing 
itself, the disposal of the waters that are produced with the 
gas does appear to be linked to increased earthquake activity. 
As evidence, Mr. Chairman, you mentioned recent research by 
USGS seismologist Bill Ellsworth and colleagues which has 
documented that magnitude 3 and larger earthquakes have 
significantly increased in the U.S. midcontinent since the year 
2000. Most of this increase in seismicity has occurred in areas 
of enhanced hydrocarbon production and hence, increased 
disposal of production related fluids.
    To understand this phenomena the key research questions 
are:
    One, what factors distinguish those injection activities 
that induced earthquakes from those that do not?
    Two, to what extent can the occurrence of earthquakes 
triggered by deep fluid injection be influenced by altering the 
operational procedures?
    Three, can small induced earthquakes trigger much larger 
tectonic earthquakes?
    Four, what will be the magnitude of the largest induced 
earthquake from a specific injection operation?
    Five, what is the probability of ground motion from induced 
earthquakes reaching a damaging level at a particular 
injectionsite?
    We're already working collaboratively with the Department 
of Energy and EPA on some of these issues in response to the 
President's establishment of the Interagency Hydraulic 
Fracturing Working Group. The involvement of industry is 
welcomed here and may be essential to make progress on some of 
these questions. Also any Federal research dollars spent to 
minimize the risk of induced seismicity will serve multiple 
goals since not only is this research relevant to natural gas 
development, geothermal development and carbon sequestration, 
but it also addresses several important gaps in our 
understanding of the natural earthquake process and fault 
behavior.
    Currently the precise data on injection volumes, rates and 
pressures needed to address these research questions are simply 
lacking for many sites of induced seismicity. Data collection 
required by underground injection control permits may not be 
sufficient to make confident, cause and effect statements about 
injection induced earthquakes after the fact. Without more 
precise and complete data it will be very difficult to assess 
the earthquake hazard potential from the tens of thousands of 
UIC wells that are currently in operation.
    Looking forward, the Administration has proposed to 
significantly increase our efforts on induced seismicity in the 
coming Fiscal year as part of a comprehensive initiative to 
address potential environmental health and safety issues 
associated with hydraulic fracturing. We hope that the Congress 
will support that initiative.
    Thank you again for the opportunity to testify. I'd be 
happy to answer any questions you may have.
    [The prepared statement of Mr. Leith follows:]

    Prepared Statement of William Leith, Senior Science Advisor for 
Earthquake and Geologic Hazards, U.S. Geological Survey, Department of 
                              the Interior
    Chairman Bingaman, Ranking Member Murkowski, members of the 
committee, thank you for inviting the U.S. Geological Survey (USGS) to 
testify at this hearing on induced seismicity. My name is Bill Leith. I 
am the Senior Science Advisor for Earthquake and Geologic Hazards at 
the U.S. Geological Survey (USGS). The USGS is the science agency for 
the Department of the Interior (DOI).
    As part of its strategy to meet future energy needs, limit 
emissions of greenhouse gases, and safely dispose of wastewater, the 
United States is expanding the use of technologies that involve the 
injection, and in some cases the associated production, of fluid at 
depth. As detailed in the report released last week by the National 
Research Council (NRC), Induced Seismicity Potential in Energy 
Technologies (hereafter, NRC report), the injection and production 
practices employed in these technologies have, to varying degrees, the 
potential to introduce earthquake hazards. I would like to commend this 
committee for requesting that such a study be undertaken and the 
Department of Energy (DOE) for funding the study. The members of the 
National Research Council panel who wrote the report have done an 
outstanding job and have made a significant and lasting contribution to 
the public discourse on this important issue.
    The USGS is well positioned to provide solutions for challenging 
problems associated with meeting the Nation's future energy needs. 
Various new approaches to produce oil and gas and alternative energy 
entail deep injection of fluid that can induce earthquakes. The cause 
and effect of induced earthquakes pose a number of risks that must be 
understood. USGS scientists, along with scientists from the National 
Labs and Universities funded by DOE, are already involved in studying a 
number of these injection projects, and we possess substantial 
expertise in the associated science and technology of mitigating the 
effects of induced earthquakes.
    I summarize here the research topics that the USGS can address in 
order to assist the Nation in meeting its future energy needs through 
an improved understanding of induced seismicity that leads to 
mitigation of the associated risks.
    To put this hazard in perspective, since the beginning of 2011 the 
central and eastern portions of the United States have experienced a 
number of moderately strong earthquakes in areas of historically low 
earthquake hazard. These include earthquakes of magnitude (M) 4.7 in 
central Arkansas on February 27, 2011; M5.3 near Trinidad, Colorado on 
August 23, 2011; M5.8 in central Virginia also on August 23, 2011; M4.8 
in southeastern Texas on October 20, 2011; M5.6 in central Oklahoma on 
November 6, 2011; M4.0 in Youngstown, Ohio, on December 31, 2011; and 
M4.8 in east Texas on May 17, 2012. Of these, only the central Virginia 
earthquake is unequivocally a natural tectonic earthquake. In all of 
the other cases, there is scientific evidence to at least raise the 
possibility that the earthquakes were induced by wastewater disposal or 
other oil-and gas-related activities. Research completed to date 
strongly supports the conclusion that the earthquakes in Arkansas, 
Colorado and Ohio were induced by wastewater injection. Investigations 
into the nature of the Oklahoma and Texas earthquakes are in progress.
    The disposal of wastewater from oil and gas production by injection 
into deep geologic formations is a process that is being used more 
frequently in recent years. The occurrence of induced seismicity 
associated with wastewater disposal from natural gas production, in 
particular, has increased significantly since the development of 
technologies to facilitate production of gas from shale and tight sand 
formations. While there appears to be little seismic hazard associated 
with the hydraulic fracturing process that prepares the shale for 
production (hydrofracturing), the disposal of waters produced with the 
gas does appear to be linked to increased seismicity, as was made 
evident by the earthquake sequence near the Dallas-Fort Worth airport 
in 2008 and 2009. In addition, recent research by USGS seismologist 
Bill Ellsworth and colleagues has documented that M3 and larger 
earthquakes have significantly increased in the U.S. mid-continent 
since 2000, from a long-term average of 21 such earthquakes per year 
between 1970 and 2000, to 31 per year during 2000-2008, to 151 per year 
since 2008. Most of this increase in seismicity has occurred in areas 
of enhanced hydrocarbon production and, hence, increased disposal of 
production-related fluids.
    Industry has been working to expand the development of 
unconventional geothermal resources known as Enhanced Geothermal 
Systems (EGS), because of their significant potential to contribute to 
the U.S. domestic energy mix. These geothermal resources are widespread 
throughout the United States and are areas of high heat flow but low 
permeability. To make EGS projects viable, the permeability of geologic 
formations must be enhanced by injecting fluid at high pressure into 
the low-permeability formations and inducing shear slip on pre-existing 
fractures. This process of permeability enhancement generally induces a 
large number of very small earthquakes with magnitudes less than 2 
(microearthquakes). The microearthquakes provide critical information 
on the spatial extent and effectiveness of reservoir creation. 
Depending on the circumstances, however, the resulting seismicity can 
have serious, unintended consequences, such as project termination, if 
any of the induced events are sufficiently large (greater than 
magnitude 4) to result in surface damage or disturbance to nearby 
residents. As a means to address these issues, the DOE published an 
induced seismicity protocol in 2012, which is cited in the NRC study as 
``a reasonable initial model for dealing with induced seismicity that 
can serve as a template for other energy technologies.''
    As emphasized in the NRC report, there is a potential seismic 
hazard associated with geologic carbon sequestration projects that 
involve the injection of very large quantities of CO2 into 
sedimentary basins, some of which are located in or near major urban 
centers of the eastern and central United States. Because carbon 
dioxide storage requires a high porosity formation of high permeability 
that is capped by an impermeable seal (e.g., shale), there are two 
important sources of seismic risk. The first type of risk is due to the 
possibility of a large magnitude earthquake that causes damage to 
structures in the environs of the project. More importantly, there is 
the possibility that an induced earthquake rupture would breach the cap 
rock allowing the CO2 to escape.
    Historically, the USGS has contributed significantly toward 
understanding seismicity induced by liquid injection, starting with the 
Rocky Mountain Arsenal in the 1960's, where it was first discovered 
that liquid waste disposal operations can cause earthquakes. Between 
1969 and 1973, the USGS conducted a unique experiment in earthquake 
control at the Rangely oil field in western Colorado. This experiment 
confirmed the predicted effect of fluid pressure on earthquake activity 
and demonstrated how earthquakes can be controlled by regulating the 
fluid pressure in a fault zone. The state of the science on the 
earthquake hazard related to deep well injection was summarized by the 
USGS in 1990, in a review that proposed criteria to assist in 
regulating well operations so as to minimize the hazard. This study was 
part of a co-operative agreement with EPA and was used to inform site 
selection and operating criteria during the development of underground 
injection control regulations for Class I Hazardous wells. This 1990 
study is the most recent review of this topic but is likely to be 
superseded by the new NRC report. With support from our partners, USGS 
scientists are currently investigating induced seismicity associated 
with brine disposal operations in the Paradox Basin of Colorado and the 
Raton Basin coal bed methane field along the Colorado-New Mexico 
border. We and our partners, including the DOE, are also investigating 
the state of stress, heat flow, and microseismicity within geothermal 
reservoirs to evaluate the effectiveness of hydraulic stimulation for 
EGS. The combination within USGS of expertise in both energy science 
and earthquake science has proven particularly effective in addressing 
current issues.
    Some of the key questions that arise in connection with fluid 
injection and production projects are:

   What factors distinguish injection activities that induce 
        earthquakes from those that do not?
   To what extent can the occurrence of earthquakes induced by 
        deep liquid-injection and production operations be influenced 
        by altering operational procedures in ways that do not 
        compromise project objectives?
   Can deep liquid-injection operations interact with regional 
        tectonics to influence the occurrence of natural earthquakes 
        by, for example, causing them to occur earlier than they might 
        have otherwise? Similarly, can induced earthquakes trigger much 
        larger tectonic earthquakes?
   What distribution of earthquakes (frequency of occurrence as 
        a function of magnitude) is likely to result from a specified 
        injection operation?
   What is likely to be the magnitude of the largest induced 
        earthquake from a specific injection operation?
   What is the probability of ground motion from induced 
        earthquakes reaching a damaging level at a particular site, and 
        what would be the consequences (e.g., injury and/or structural 
        damage)?

    In the recent NRC report and in workshops sponsored by the DOE, , a 
common need has been identified for research to address the science 
questions posed above. The USGS, as an independent and unbiased science 
organization, can play a major role in studying, assessing, and 
providing solutions to these problems. We are already working 
collaboratively with DOE and U.S. Environmental Protection Agency on 
some of these issues, in response to the President's establishment of 
the interagency hydraulic fracturing working group, as well as with the 
States.
    Although our primary research is directed at natural earthquakes 
and hydrogeology, we have in the past assessed the hazards associated 
with induced earthquakes due to mining operations, reservoir 
impoundment, oil and gas production and fluid injection. Thus, for many 
of these items, the research would mostly involve modifying existing 
approaches to the specialized requirements of fluid injection-and 
production-induced earthquakes.
    Addressing these science problems will require a multidisciplinary 
approach that includes research in seismology, hydrology, crustal 
deformation, laboratory rock mechanics, in situ stress and fracture 
permeability, heat transport, fluid flow and other areas of study. The 
research activities might potentially include field-scale experiments, 
laboratory rock mechanics experiments, and the development and 
application of numerical models that simulate the effects of fluid 
injection operations on fracturing, fault reactivation and stress 
transfer, especially in low-permeability formations. Careful analyses 
of published case histories involving seismicity caused by fluid 
injection and production operations would be an important component of 
a comprehensive research program.
    The involvement of industry is welcomed and may be essential to 
make progress on many of the key science questions. We see value in 
establishing an experimental site, or sites, in cooperation with 
industry and other agencies that could further the early work on 
induced earthquake triggering that was conducted so long ago at the 
Rangely field in Colorado. We note that DOE has in fact proposed a 
government-managed test site for EGS in its FY13 budget proposal, at 
which such R&D could be conducted in a carefully controlled and 
instrumented environment.
    While a comprehensive effort is needed, and is called for in the 
NRC's recent report, any federal research dollars spent to minimize the 
risks of induced seismicity will serve multiple goals. Not only is this 
research relevant to shale gas development, geothermal development and 
carbon sequestration, but it also addresses several important gaps in 
our knowledge of the natural earthquake process and fault behavior.
    I wish to expand on two of the findings and recommendations in the 
NRC report:

    The first of these is what I will call the ``data gap'', for which 
the report recommends, ``Data related to fluid injection... should be 
collected by state and federal regulatory authorities in a common 
format and made publicly available (through a coordinating body such as 
the USGS).'' Currently, the data on injection volumes, rates and 
pressures needed to address many of the research questions above are 
simply lacking for many sites of induced seismicity. Permitting 
requirements for Underground Injection Control (UIC) wells are defined 
under Safe Drinking Water Act regulations, administered by the EPA and 
the states. Unless the potential for induced seismicity has been 
identified as a local risk prior to issuing a UIC permit, data 
collection required under these permits may not be sufficient to make 
confident cause-and-effect statements about injection-induced 
earthquakes after the fact, making it difficult to provide useful 
information to the regulating authorities about whether a particular 
disposal operation has or will have increased local earthquake risk.
    Without more precise and complete data, it will be very difficult 
to assess the hazard potential from the tens of thousands of UIC wells 
that are currently in operation and for which their earthquake 
potential is unknown. An equal challenge is posed by UIC wells that may 
be permitted and become active injectors in the future, particularly if 
the permitting agency for the well is not cognizant of the associated 
earthquake hazard, or not in communication with parties that would be 
sensitive to a change in earthquake risk. For example, how close to an 
existing nuclear power plant or a dam is ``too close'' to site a 
disposal well permitted for a specified volume and pressure? Whose 
responsibility is it to evaluate the risk? Who is responsible for 
notifying the parties at risk? Who carries the liability should a 
damaging earthquake occur? Getting answers to these questions requires 
accurately assessing the induced-earthquake hazard, but at present the 
needed statistics are lacking because of the data gap. The NRC report 
provides some helpful guidance on how to develop ``best practice'' 
protocols that could help to close the data gap if implemented The 
report cites the recently published DOE IS protocol as an important 
step towards establishing a best practices effort.
    The NRC report also found: ``To date, the various agencies have 
dealt with induced seismic events with different and localized actions. 
These efforts to respond to potential induced seismic events have been 
successful but have been ad hoc in nature.'' Above in this testimony, I 
detailed the large number of induced or potentially induced earthquakes 
that have occurred in 2011 and 2012. Further, USGS scientists have also 
documented a seven-fold increase since 2008 in the seismicity of the 
central U.S., an increase that is largely associated with areas of 
wastewater disposal from oil, gas and coal-bed methane production. 
Scientifically, USGS has a depth of expertise relevant to understanding 
induced seismicity and the increasing demand for better monitoring, 
analysis, assessment, and public information. We have also worked 
closely with colleagues in academia and the State Geological Surveys, 
which have also seen increasing demands.
    To meet these increasing demands, we have increased research 
efforts within our current budget. Looking forward, the Administration 
has proposed to significantly increase our efforts on induced 
seismicity in the coming fiscal year, as part of a comprehensive 
initiative to address potential environmental, health, and safety 
issues associated with hydraulic fracturing, and we hope that the 
Congress will support that initiative.
    Thank you again for the opportunity to testify and for your 
attention to this important matter. I would be happy to answer any 
questions you may have.

    The Chairman. Thank you very much.
    Ms. Petty.

   STATEMENT OF SUSAN PETTY, PRESIDENT AND CHIEF TECHNOLOGY 
           OFFICER, ALTAROCK ENERGY, INC, SEATTLE, WA

    Ms. Petty. Thank you, Mr. Chairman and members of the 
committee. Good morning.
    I really appreciate this opportunity to talk to you about 
our experiences with the mitigation of induced seismicity in 
the geothermal industry. Over the past few years injection 
induced seismicity has become an increasingly important issue 
that Earth scientists working in the geothermal, mining, 
petroleum and other industries must address. At Altarock Energy 
we're in the trenches focused on developing advanced technology 
to reduce the cost of enhanced geothermal systems to extend the 
ability to use this base load renewable energy source across 
the United States.
    This resource is so large that recovering even a small 
fraction of it could provide electric power and heat sufficient 
to supply 10 percent or more of the Nation's need for thousands 
of years to come. The MIT study of the future of geothermal 
energy in 2007 projected that there is the potential to 
generate over 2 million megawatts across the U.S. if only 2 
percent of this resource can be recovered. The USGS found that 
there is the potential for more than 500,000 megawatts in the 
Western United States alone.
    In order to develop this vast resource we need a way to 
recover the heat by injecting water into a well, have it move 
through the hot rock and pick up heat and then be produced 
through production wells. To do this, we create a network of 
fine fractures that access a large volume of hot rock. Doing 
this requires pumping cold water into the ground at relatively 
modest pressures and then using the temperature contrast 
combined with the pressure to extend existing fractures and 
planes of weakness outward from the well.
    While this is not new technology, it is technology that is 
still in development. Advances are needed to both reduce the 
risks associated with the development and to improve economics. 
One of the areas of risk is the possibility that seismicity of 
concern to people will be induced during the process of 
creating the reservoir or operating the EGS project long term. 
By looking at our past experiences with injection and induced 
seismicity, we can gain a better understanding of how to select 
project sites with--and operate the reservoir, so that we can 
reduce the risk of problematic induced seismicity. Our 
experience with the Newberry EGS Demonstration Projects, I 
feel, can help us grasp the issues and the potential solutions 
to these issues that will affect any future projects that use 
EGS technology.
    Injection induced seismicity occurs when the fluid pressure 
in a fault or fracture reaches a critical value above which the 
friction preventing slip is overcome.
    This concept was proposed in 1959.
    Inadvertently demonstrated at the Rocky Mountain Arsenal in 
1962.
    Further tested at the Rangely Oil Field in 1969.
    Has been incorporated into continuous injection operations 
at Paradox Valley since 1996.
    EGS reservoir creation relies upon controlled induced 
seismicity to create the high surface area fracture paths 
needed for sustainable and economic heat extraction. The 
lessons learned from past EGS projects, in particular to 
projects along the Rhine Garben in Europe, are being used to 
refine the plans for future projects.
    It's important to understand that creation of the EGS 
reservoir necessarily causes tiny seismic events when the small 
fractures slip and slide against one another. We use these tiny 
seismic events, as does the oil and gas industry, to map the 
fractures as we form them. What we don't want is larger faults 
to slip during this process and release enough energy for 
people to feel.
    The energy released measured by the moment magnitude, 
commonly thought of as the Richter scale, is only one aspect of 
whether the seismicity will be felt by people or not. The rocks 
that the energy passes through and the types of soils near the 
surface as well as the structures that sit on those soils all 
contribute to whether seismicity is problematic or not.
    One of the things we need to do to better communicate about 
injection induced seismicity is understand that that 
relationship between the magnitude of the event at depth and 
what people might potentially feel on the surface, the ground 
shaking. It would be better to talk about the risk of ground 
shaking than to talk about the risk around a particular 
magnitude of event occurring. I might add that the mining 
industry has long had regulations regarding ground shaking that 
we can maybe look to, to get this kind of experience.
    For the Newberry EGS demonstration project we have gone 
through a process of both developing an induced seismicity 
mitigation protocol for the project activities and also 
communicating with the public about the project and the issues 
associated with induced seismicity. Three Federal agencies were 
involved with the permitting process, the Department of Energy, 
the Bureau of Land Management and the Forest Service. Only the 
DOE had staff with expertise in induced seismicity to help us 
through the process. We had, therefore, to inform and educate 
other regulators about the methods used to assess the potential 
risks related to induced seismicity and the possibilities for 
mitigating those risks.
    The most difficult part of the induced seismicity hazards 
assessment was commuting the information it contains to the 
public. The ability of scientists to explain risk to the 
general public is limited by the public's familiarity with that 
risk. Using maps and graphics help, but the language we have 
for discussing seismicity is difficult for the best of us to 
relate to our everyday lives.
    One of the interesting aspects of our public outreach 
effort is that in this region of tectonic activity with 
volcanoes and subduction zones as well as offshore large faults 
and fractures, people are much more concerned with potential 
for ground water contamination or water use impacts than they 
are with induced seismicity. While the Newberry area itself is 
very seismically quiet and quite remote from people, Oregonians 
are regularly rattled by temblors mostly on offshore faults. So 
they are familiar with small, natural seismic events.
    On the other hand this is arid area with little water and 
little rainfall. Water is of key importance. It's in scarce 
supply. The focus by the regulators on induced seismicity took 
attention away from the key issue for the public which is 
water.
    The result of a public outreach on our communication with 
regulators, as well as the expert input of the DOE, was a 
mitigation protocol that should enable us to both conduct our 
project and reduce the risk of felt seismicity. Our effort at 
Newberry is far more extensive and in depth. What is required 
of operators of waste water disposal wells with the risk, based 
on past experience, is far higher than what we have at 
Newberry.
    What can we take away from our experience with the Newberry 
project and with other EGS projects?
    Project citing can help us to reduce the risk and also the 
concerns of the public about that risk. We need to site 
projects away from large populations and dense populations 
until we better understand the risks surrounding this 
technology.
    We need to avoid areas with large faults. How far away do 
we need to be from those faults? We don't yet know. That's 
something that needs further research.
    Existing background data on seismicity is crucial for site 
selection and for gathering the information needed for 
permitting and operation of these sites.
    Public outreach is very important. But communication with 
regulators is equally so. Risk assessment results are difficult 
to explain to both the public and to regulators. So we need to 
select experts to write up and communicate these results, who 
have excellent communication skills.
    Graphics are needed. But they need to be easy to explain 
and understand.
    We also need to work with the press to get the message 
across. We have to provide data and graphics to reporters to 
help them understand the project. I have to say that this has 
been one area that has really been very difficult. I think has 
resulted in a lot of misunderstanding about what's going on in 
this technology.
    We also need to identify key local issues. We don't want to 
let induced seismicity dominate the discussion if it isn't the 
key issue.
    Induced seismicity mitigation protocol for all injection 
related projects in the energy interest--industry that's 
consistent across the technologies would be a useful tool for 
both project developers and regulators.
    Thank you.
    [The prepared statement of Ms. Petty follows:]

   Prepared Statement of Susan Petty, President and Chief Technology 
              Officer, Altatrock Energy, Inc. Seattle, WA





    The Chairman. Thank you very much.
    Dr. Zoback.

  STATEMENT OF MARK D. ZOBACK, BENJAMIN M. PAGE PROFESSOR OF 
EARTH SCIENCES, DEPARTMENT OF GEOPHYSICS, STANFORD UNIVERSITY, 
                          STANFORD, CA

    Mr. Zoback. Chairman Bingaman, Senator Murkowski and 
committee members, thank you for asking me to testify today.
    My name is Mark Zoback. I'm a Professor of Geophysics at 
Stanford University. My field of expertise is in quantifying 
the geologic processes in the Earth that control earthquakes 
and hydraulic fracture propagation. I've been doing this 
research for over 30 years.
    While I was not a member of the NRC Committee chaired by 
Professor Hitzman, I did have the opportunity to speak to them 
about the issues I'll talk to you about today. Let me say at 
the outset, that I'm in full agreement with the principle 
findings of their report.
    I want to limit my comments today to discussing earthquakes 
and energy technologies in 2 specific contexts.
    First will be the earthquakes triggered by injection of 
waste water. Of course of particular interest has been the 
injection of the flow back water coming out from shale gas 
wells following hydraulic fracturing.
    Second, I want to comment briefly about the potential for 
triggered seismicity associated with the large scale carbon 
capture and storage or CCS, as it is widely known.
    As Dr. Leith pointed out, in 2011 the relatively stable 
interior of the U.S. was struck by a surprising number of small 
to moderate size, but still widely felt earthquakes. Most of 
these events, as he indicated, were the kinds of natural events 
that occur from time to time in intra-plate regions. But a 
number of the small to moderate earthquakes that did occur in 
2011 appeared to be associated with the disposal of waste 
water, at least in part related to shale gas production. 
Seismic events associated with waste water in 2011 include the 
earthquakes near Guy, Arkansas and those near Youngstown, Ohio.
    It is understandable that the occurrence of injection 
related earthquakes is of concern to the public, the government 
and industry alike. I think it is clear that with proper 
planning, monitoring and response, the occurrence of small to 
moderate earthquakes associated with waste injection can be 
reduced and the risks associated with these events effectively 
managed.
    Five straight forward steps can be taken to reduce the 
probability of triggering seismicity whenever we inject fluid 
into the subsurface.
    First, and as Susan Petty just pointed out, we need to 
avoid injection into faults in brittle rock. While this may 
seem like a no-brainer, there's not always a sufficient site 
characterization prior to approval of an injectionsite. In fact 
EPA guidelines does not include the consideration of triggered 
seismicity among its requirements.
    Second, formations need to be selected that minimize the 
pore pressure changes. It is the increase of pore pressure that 
is the problem. We can minimize that increase in pore pressure 
by careful selection of formations used for injection.
    Third, local seismic monitoring arrays should be installed 
when there is a potential for triggered seismicity.
    Fourth, protocols should be established in advance to 
define how operations would be modified if seismicity were to 
be triggered.
    These kinds of proactive steps, I think, will go a long way 
toward making the rare occurrence of these events even more 
rare and assure the public that their safety is being 
protected.
    I'd now like to comment briefly about the potential for 
triggered seismicity associated with large scale carbon capture 
and storage. My colleague, Steve Gorelick and I, have recently 
pointed out that not only would large scale CCS be an extremely 
costly endeavor, there is a high probability that earthquakes 
will be triggered by injection of the enormous volumes of 
CO2 associated with large scale CCS in many regions 
currently being considered.
    There are 2 issues I want to emphasize in particular.
    First, our principle concern is not the probability of 
triggering large earthquakes. Large faults are required to 
produce large earthquakes. We assume that such faults would be 
detected and thus avoided by careful site characterization 
studies.
    Our concern is that even small to moderate size earthquakes 
would threaten the seal integrity of the formations being used 
to store the CO2. Studies by other scientists have 
shown that a leak rate from an underground CO2 
storage reservoir of less than 1 percent per thousand years is 
required for CCS to achieve the same climate benefits as 
switching to renewable energy sources.
    Second, it's important to emphasize that we recognize that 
CCS can be a valuable and useful tool for reducing greenhouse 
gas emissions in specific situations. Our concern is whether 
CCS can be a viable strategy for achieving global greenhouse 
gas reductions and appropriate positive effects on climate 
change. From a global perspective, if large scale CCS is to 
significantly contribute to reducing the accumulation of 
greenhouse gases, it must operate at a massive scale on the 
order of the volume injected has to be on the order of the 27 
billion barrels of oil that are produced each year around the 
world. So it's a truly massive undertaking.
    Now multiple lines of evidence indicate that pre-existing 
faults found in brittle rocks almost everywhere in the Earth's 
crust are close to frictional failure. In fact, over time 
periods of just a few decades, modern seismic networks have 
shown us that earthquakes occur nearly everywhere in 
continental interiors.
    So in the light of the risk posed to a CO2 
repository by even small to moderate sized earthquakes, 
formations for suitable large scale injection of CO2 
must be well sealed by impermeable overlying strata.
    They must be weakly cemented so as to not fail through 
brittle faulting.
    They must be porous, permeable and laterally extensive to 
accommodate large volumes of CO2 with minimal 
pressure increases.
    Thus the issue is not whether CO2 can be safely 
stored at a given site. The issue is whether the capacity 
exists for sufficient volumes of CO2 to be stored in 
geologic formations for it to have a beneficial effect on 
climate change. In this contest--in this context, it must be 
recognized that large scale CCS will be an extremely expensive 
and risky strategy for achieving significant reductions in 
greenhouse gas emissions.
    Mr. Chairman, Senator Murkowski, members of the committee, 
thank you for the opportunity to speak to you today.
    [The prepared statement of Mr. Zoback follows:]

  Prepared Statement of Mark D. Zoback, Benjamin M. Page Professor of 
    Earch Sciences, Department of Geophysics, Stanford University, 
                              Stanford, CA
    Chairman Bingaman, Senator Murkowski and members of the committee, 
thank you for asking me to testify today. My name is Mark Zoback, I am 
a Professor of Geophysics at Stanford University. For your general 
information, I last spoke to this committee in October as a member of 
the Secretary of Energy's Advisory Board Shale Gas Subcommittee. I also 
served on the National Academy of Engineering committee that 
investigated the Deepwater Horizon accident. My field of expertise is 
in quantifying geologic processes in the earth that control earthquakes 
and hydraulic fracture propagation. I have been doing research in these 
fields for over 30 years ago. My PhD students and I have been carrying 
out a number of collaborative research projects seeking to better 
understand these processes in the context of carbon capture and storage 
and production from shale gas reservoirs.
    While I was not a member of the NRC committee chaired by Professor 
Hitzman, I did have the opportunity to speak with the committee about 
the issues I'll comment upon today. Let me say at the outset that I am 
in full agreement with the principal findings their report.
    Today, I will limit my comments to discussing earthquakes and 
energy technologies in two specific contexts. First, will be 
earthquakes triggered by injection of wastewater. While wastewater can 
come from many sources, of particular interest in the past few years 
has been the injection of the flow-back water coming out of shale gas 
wells following hydraulic fracturing. Second, I want to comment briefly 
about the potential for triggered seismicity associated large-scale 
carbon capture and storage, or CCS, as it is widely known.
    In most cases, if earthquakes are triggered by fluid injection it 
is because injecting fluid increases the pore pressure at depth. The 
increase in pore pressure reduces the frictional resistance to slip on 
pre-existing faults, allowing elastic energy already stored in the rock 
to be released in earthquakes. For the cases I will speak about today, 
the earthquakes in question would have occurred someday as a natural 
geologic process--injection could simply advance their time of 
occurrence.
    I have provided the committee staff with recently published papers 
I've written on these topics to provide more details.
Earthquakes associated with wastewater injection
    In 2011 the relatively stable interior of the U.S. was struck by a 
surprising number of small-to-moderate, but widely felt earthquakes. 
Most of these were natural events, the types of earthquakes that occur 
from time to time in all intraplate regions. The magnitude 5.8 that 
occurred in northern Virginia on Aug. 23, 2011 that was felt throughout 
the northeast and damaged the Washington Monument was one of these 
natural events. While the magnitude of this event was unusual for this 
part of the world, the Aug. 23rd earthquake occurred in the Central 
Virginia seismic zone, an area known for many decades to produce 
relatively frequent small earthquakes.
    This said, a number of the small-to-moderate earthquakes that 
occurred in the interior of the U.S. in 2011 appear to be associated 
with the disposal of wastewater, at least in part related to shale gas 
production.
    Following hydraulic fracturing of shale gas wells, the water that 
was injected during hydraulic fracturing is flowed back out of the 
well. The amount of water that flows back after fracturing varies from 
region to region. It's typical for 25-50% of injected water to flow 
back. While the chemicals that comprise the fracturing fluid are 
relatively benign, the flow-back water can be contaminated with brine, 
metals and potentially dangerous chemicals picked up from the shale and 
must be disposed of properly.
    Seismic events associated with injection of wastewater in 2011 
include the earthquakes near Guy, Ark., where the largest earthquake 
was a magnitude-4.7 event on Feb. 27th and the earthquakes that 
occurred on Christmas Eve and New Year's Eve near Youngstown, Ohio. The 
largest Youngstown event was magnitude 4.0. It is understandable that 
the occurrence of injection-related earthquakes is of concern to the 
public, government officials and industry alike.
    I believe that with proper planning, monitoring and response, the 
occurrence of small-to-moderate earthquakes associated with fluid 
injection can be reduced and the risks associated with such events 
effectively managed. No earthquake triggered by fluid injection has 
ever caused serious injury or significant damage. Moreover, 
approximately 140,000 Class II wastewater disposal wells have been 
operating safely and without incident in the U.S. for many decades.
    Five straightforward steps can be taken to reduce the probability 
of triggering seismicity whenever we inject fluid into the subsurface. 
First, it is important to avoid injection into faults in brittle rock. 
While this may seem a ``no-brainer'', there is not always sufficient 
site characterization prior to approval of a injection site. Second, 
formations should be selected for injection (and injection rates 
limited) so as to minimize pore pressure changes. Third, local seismic 
monitoring arrays should be installed when there is a potential for 
injection to trigger seismicity. Fourth, protocols should be 
established in advance to define how operations would be modified if 
seismicity were to be triggered. And fifth, operators need to be 
prepared to reduce injection rates or abandon injection wells if 
triggered seismicity poses any hazard. These five steps provide 
regulators and operating companies with a framework for reducing the 
risk associated with triggered earthquakes.
    In addition, the re-cycling of flow-back water (for use in 
subsequent hydraulic fracturing operations) is becoming increasingly 
common (especially in the northeastern U.S.). This is a very welcome 
development. Re-use of flow-back water avoids potential problems 
associated with transport and injection flow-back water or the expense 
and difficulty of extensive water treatment operations.
    It is important to note that the extremely small microseismic 
events occur during hydraulic fracturing operations. These microseismic 
events affect a very small volume of rock and release, on average, 
about the same amount of energy as a gallon of milk falling off a 
kitchen counter. The reason these events are so small is that 
pressurization during hydraulic fracturing affects only limited volumes 
of rock (typically several hundred meters in extent) and pressurization 
typically lasts only a few hours. A few very small earthquakes have 
occurred during hydraulic fracturing (such as a magnitude-2.3 
earthquake near Blackpool, England, in April 2011), but such events are 
extremely rare.
    It is important for the public to recognize that the risks posed by 
injection of wastewater are extremely low. In addition, the risks can 
be minimized further through proper study and planning prior to 
injection, careful monitoring in areas where there is a possibility 
that seismicity might be triggered, and operators and regulators taking 
a proactive response if triggered seismicity was to occur.
Earthquake potential and large-scale carbon storage
    I would now like to comment briefly about the potential for 
triggered seismicity associated large-scale carbon capture and storage. 
My colleague Steve Gorelick and I have recently pointed out that not 
only would large-scale CCS be an extremely costly endeavor, there is a 
high probability that earthquakes will be triggered by injection of the 
enormous volumes CO2 associated with large-scale CCS.
    There are two issues I wish to emphasize in particular this 
morning. First, our principal concern is not the probability of 
triggering large earthquakes. Large faults are required to produce 
large earthquakes. We assume that such faults would be detected, and 
thus avoided, by careful site characterization studies. Our concern is 
that even small-to-moderate size earthquakes would threaten the seal 
integrity of the formations being used to store CO2 for long 
periods without leakage. Studies by other scientists have shown that a 
leak rate from underground CO2 storage reservoirs of less 
than 1% per thousand years is required for CCS to achieve the same 
climate benefits as switching to renewable energy sources.
    Second, it is important to emphasize that we recognize that CCS can 
be a valuable and useful tool for reducing greenhouse gas emissions in 
specific situations. Our concern is whether CCS can be a viable 
strategy for achieving appreciable global greenhouse gas reductions. 
From a global perspective, if large-scale CCS is to significantly 
contribute to reducing the accumulation of greenhouse gases, it must 
operate at a massive scale, on the order of 3.5 billion tonnes of 
CO2 per year. This corresponds to a volume roughly 
equivalent to the 627 billion barrels of oil currently produced 
annually around the world.
    Multiple lines of evidence indicate that pre-existing faults found 
in brittle rocks almost everywhere in the earth's crust are close to 
frictional failure, often in response to small increases in pore 
pressure. In fact, over time-periods of just a few decades, modern 
seismic networks have shown that earthquakes occur nearly everywhere in 
continental interiors. In light of the risk posed to a CO2 
repository by even small-to-moderate size earthquakes, formations 
suitable for large-scale injection of CO2 must be well-
sealed by impermeable overlaying strata, weakly cemented (so as not to 
fail through brittle faulting) and porous, permeable, and laterally 
extensive to accommodate large volumes of CO2with minimal 
pressure increases.
    Thus, the issue is not whether CO2 can be safely stored 
at a given site, the issue is whether the capacity exists for 
sufficient volumes of CO2 to be stored in geologic 
formations for it to have a beneficial affect on climate change. In 
this context, it must be recognized that large scale CCS will be an 
extremely expensive and risky strategy for achieving significant 
reductions in greenhouse gas emissions.
    Mr. Chairman, Senator Murkowski and members of the committee, thank 
you for the opportunity to speak to you today.

    The Chairman. Thank you all very much for the excellent 
testimony. Let me start with a few questions.
    Dr. Hitzman, I'm trying to get clearly in mind the main 
thrust of your conclusions. From what I believe I heard you say 
and have read in your report here, the 2 biggest potential 
causes of this seismic activity, human causes, would be 
injection of waste water which is a significant issue because 
there's a lot of it injected.
    Second, if in fact we were to pursue carbon capture and 
storage at a large scale that also would be significant.
    That those 2 types of injection pose a much greater threat 
and are a much greater issue, in your mind, then the injection 
that is generally referred to as fracking and geothermal 
activity as well as I understand it. Is that a reasonable 
summary of your----
    Mr. Hitzman. That's a very fair statement of what the 
report says. Yes.
    The Chairman. So you're not as worried about fracking. 
You're not as worried about geothermal energy production 
activities.
    But you are worried about waste water and you are worried 
about CCS if it goes to a large scale?
    Mr. Hitzman. Correct. It really is volume dependent.
    So in geothermal we're trying to balance a reservoir.
    In fracking there's very small volume.
    But in waste water, most of the waste water disposal wells 
are fine. But with vast numbers of them and putting lots and 
lots of these wells in, some of them with fairly large volumes, 
occasionally there will be an event.
    CCS, because it has such very large volumes, as pointed out 
by Dr. Zoback, are sort of in a different league. So that 
clearly is of concern.
    The Chairman. Now as far as I understand, to deal with 
the--or to reduce the likelihood that you're going to have 
human felt induced seismic activity from waste water injection. 
I think your suggestion is that there are some best practices 
that can be followed. I guess my question there is, is it clear 
that who would have the responsibility or authority to define 
those best practices and try to implement them or is this 
such--you've got so many agencies and so many different levels 
of government involved here that the whole thing is a 
hodgepodge?
    Mr. Hitzman. The committee actually didn't try to specify 
who should do it because, as you say, there are a number of 
agencies and different groups involved. But clearly, sort of as 
happened with the DOE protocol for EGS. What took place there 
was a cooperative venture between several levels of government 
with academia, with industry, with local communities try and 
come up with best practices.
    The committee felt that that was the sort of way moving 
forward with the other energy technologies as well.
    The Chairman. So the Department of Energy or EPA or 
somebody at the Federal level could convene a group of all the 
various players in this field and try to come up with some kind 
of guidelines. Say this is what we need to be doing in order to 
reduce the likelihood of this seismic activity resulting from 
waste water injection.
    Mr. Hitzman. Yes, absolutely.
    The Chairman. Yes.
    Now what's your reaction to Dr. Zoback's comment?
    He's made a very interesting point here which is basically 
that he thinks that, as I understand it, and Dr. Zoback correct 
me if I misstate your view here. But your basic view is that in 
order for carbon capture and storage to be pursued on the large 
scale that it would have to be pursued in order to achieve 
significant climate change benefits or, you know, we have real 
problems in pursuing it at that scale considering the 
likelihood of leakage out of these underground storage 
facilities.
    Is that a fair summary of--maybe you can state it much 
better than that.
    Mr. Zoback. I'll try.
    When we look at the global greenhouse gas problem, you 
know, the real problem is that by mid-century the--if we do 
nothing emissions will be twice as much as they are today. So 
we'll be adding, you know, something like 15 billion tons of 
carbon to the atmosphere per year in 2050. You know, we're 
currently at the 7 or 8 billion ton level.
    So we have a problem that's on the scale of needing to 
reduce emissions by 7 or 8 billion tons of carbon. Now if CCS 
is going to be part of that solution at that scale it has been 
proposed that it should deal with say, one seventh or one 
eighth of the problem.
    Can it go along with, you know, enhanced use of renewables?
    Can it go along with energy efficiency programs?
    Can it go along with fuel switching from coal to natural 
gas?
    All of which will reduce emissions.
    If it's going to be a player at the billion ton level then 
we get into a situation where we need 3,500 projects of the 
scale of the single operable project that's going on now in the 
North Sea. So it's really not the fact that we can't find good 
places to put CCS. But for CCS to be part of a global strategy 
for stabilizing emissions it's got to operate at this billion 
ton of carbon scale which is 3,500 times what we're doing today 
at a single site.
    The Chairman. OK.
    Why don't I defer to Senator Murkowski for her questions 
and then Senator Landrieu?
    Senator Murkowski. Thank you, Mr. Chairman.
    I appreciate the testimony from all the witnesses this 
morning. Very interesting. I think that the focus here on CCS 
and waste water injection is an interesting one. Perhaps the 
results of this study were different than what some imagined 
before you began this.
    But let me ask the question again, sticking with the CCS. I 
mean we've got new EPA rules that essentially ban construction 
of new coal fired power plants unless CCS is out there. So a 
lot of interest in whether or not we can do this right and/or 
if at all.
    More specific perhaps to this committee is the work that 
we've done to draft the liability protections for CCS 
operators. So I guess the question to you, Dr. Hitzman, is with 
this information that we know have do you think that it is 
perhaps premature or even unwise to provide liability 
protection for CCS operators? I mean, can we even do this or do 
we need to know more?
    Mr. Hitzman. That certainly is outside the scope of what 
our committee looked at. We did not look at insurance 
whatsoever. So where we can down to is that there is 
significant concerns. We thought that DOE should address those 
concerns to look at how this technology may play out in the 
large scales that Dr. Zoback has talked about.
    Senator Murkowski. You--we're talking now about the 
increased risk, comparative, when we're talking about 
geothermal or fracking as it relates to waste water injection 
and CCS. But is it--it's not fair to describe that the risk or 
the consequences between waste water injection and CCS are 
comparable. Is that correct?
    I mean, you've got a higher risk with CCS?
    Mr. Hitzman. It depends on the volumes. So it's volume 
related. If we were injecting billions of tons, as Dr. Zoback 
discussed, then the risks are probably much greater because 
certainly none of our waste water wells are injecting anywhere 
near that.
    So really it's--think about volume. The more volume 
probably the more risk.
    Senator Murkowski. You made a statement that, let's see, no 
geologic review before injection. This is with the disposal of 
the waste water. Is that, perhaps, part of the reason that we 
see higher rates of seismic activity is because you don't have 
that same geologic study that you have, say for instance, when 
you're doing a geothermal well or even fracking?
    You've got some pretty serious studies that proceed before 
you move forward. Is that perhaps accounting for some of the 
difference?
    Mr. Hitzman. That's part of it, yes. With any of the CCS 
projects going on, with certainly with geothermal, we have a 
lot of geologic data before those happen.
    For many waste water wells they're relatively low cost 
operations. They don't have a lot of citing--site 
characterizations done ahead of time.
    But it also is important to note that the vast majority of 
waste water wells do not have an issue. So we're not, in the 
report, we certainly do not suggest requiring that that occur 
for all waste water wells.
    Senator Murkowski. OK.
    Dr. Leith, let me ask you about monitoring. Both the report 
and your testimony indicate that we need greater monitoring 
activity. In terms of scale do we need to double the monitoring 
that we're doing?
    What would you suggest in terms of stepped up monitoring 
activities here?
    Mr. Leith. The USGS, the National Seismic Network, is 
capable of routinely locating earthquakes that are around 
magnitude 3 and in many areas lower than that. But with that 
network we certainly cannot detect the onset of low magnitude 
induced earthquakes from an injection operation in most of the 
country.
    So what we rely upon is learning early about the occurrence 
of earthquakes. That typically doesn't happen until they're 
felt. It's just going to be above magnitude two somewhere.
    Then deploying portable seismometers to go in and assess 
what's going on. This is what we did in Arkansas and in 
Oklahoma and----
    Senator Murkowski. Do you do that just in a few specific 
areas or is--are you doing this monitoring across the country?
    Mr. Leith. We do not have enough portable systems to deploy 
to all of the interesting cases of induced seismicity.
    Senator Murkowski. If you have enough portable systems in 
these interesting areas, as you put it, what would that 
require?
    Mr. Leith. We have been so busy with natural earthquakes 
for the last few years. Then this increased occurrence of 
induced earthquakes has piled onto that demand.
    We would need, I would estimate, some hundreds of portable 
systems to respond to just the earthquakes that are in the 
magnitude 4 and above range. That, of course, doesn't include 
the scientist's time, the analyst to evaluate the data and the 
researchers to then correlate what's recorded by the 
seismometer to determine its relation to the injection 
activity, the fluid volumes injected, the pressures and those 
sort of things.
    Senator Murkowski. Thank you, Mr. Chairman.
    The Chairman. Senator Landrieu.
    Senator Landrieu. Thank you very much. I have a short 
statement for the record.
    Senator Landrieu. I want to say I really appreciate the 
hearing the chairman and the ranking member have put together. 
This is very, very interesting, particularly about the volume 
necessary, the 3,500 sites, to take care of the billion tons of 
carbon sequestration.
    Let me ask you, if you could, Dr. Zoback, to describe these 
locations to the best of your ability to those of us that are 
trying to get our heads around what such a location might look 
like. You said there would need to be 3,500 sites. So we could 
pick 100 countries, put 35 in each one.
    How--what would a site look like? Describe the one that 
exists now so we can get a little better understanding of that.
    Mr. Zoback. The project that exists now is a gas field. 
It's operating in the North Sea. When they produce the gas it 
has a large fraction of CO2 mixed with the methane. 
So they have to deal with the CO2.
    They separate it from the natural gas. Put the natural gas 
into a pipeline. Then they have an injection well in which they 
inject the CO2 into a geologic formation, basically 
above the gas reservoir. This geologic formation has, what I 
consider to be, you know, ideal characteristics.
    First, it's very laterally extensive. It's big. So you're 
putting the CO2 into a large volume.
    Senator Landrieu. It's right near the site itself.
    Mr. Zoback. That's exactly right. It's--the well has been 
drilled off the same platform that the gas wells were drilled 
from.
    So the geologic formation, it's called the Utsira 
formation. It's a very--it's laterally extensive. It's very 
porous and permeable so it's easy for them to get the 
CO2 into it. It has this added characteristic that 
it's very weak and friable.
    It's easy to imagine that if you had a very weak sandstone 
and you squeezed on it, well it would just kind of deform 
slowly in your hands and, you know, there's no problem. Whereas 
a very strong rock, as you squeeze on it, it holds the force 
much better. But when it does fail it will fail brittle-ly. You 
know, it's like a very small earthquake.
    So the Utsira formation is porous, permeable, laterally 
extensive and very weak and located where you want it to be. 
It's absolutely ideal.
    Senator Landrieu. Let me follow that up. Because I was 
thinking that it would have to be on countries, on land. But 
this could be 3,500 sites in the world in the oceans, on land, 
etcetera, etcetera.
    So while it sounds like a lot of sites, you know, it's a 
big planet. So I think we have to get the scale of this to 
understand. But I think it's a very important point that you 
raised.
    But it's also, I would say in response, while it seems 
overwhelming when you first say it. Until you've had a little 
bit more information about how many other potentially, really 
enormous and very good sites there might be. Before we 
completely rule this out we need to have a little bit more, a 
lot more, data about that.
    Let me ask my other question.
    I'm very pleased to hear that fracking is not the problem. 
We've heard a lot of problems about fracking. Since my State is 
doing a lot of it and think we're contributing to the natural 
gas production which is helping clean our atmosphere and 
provide the energy that our Nation and the world needs to move 
forward. But it's the waste water injections.
    So I want to ask a couple of questions.
    Is the oil and gas industry, primarily in the United 
States, responsible for the majority of waste water wells? Are 
there other industries that are injecting waste water? Could 
somebody give us some data, if you have it, about that?
    Is it primarily the oil and gas industry or is it primarily 
other mining or is it petrochemical or agriculture, etcetera, 
etcetera?
    Mr. Hitzman. There's some data in the NRC report. I don't 
have at the top of my head the percentage. But there are a 
number of producers of waste water that are disposed in the 
subsurface. Oil and gas is one of the major ones in the 
country.
    Senator Landrieu. But there are other major ones?
    Mr. Hitzman. There are other major ones.
    Senator Landrieu. Are there any industries that are more 
than the oil and gas industry? Does anybody know? You think 
there would be----
    Mr. Hitzman. I think it probably is the single largest. But 
it's probably not super high above.
    Senator Landrieu. Above the others.
    Mr. Hitzman. Some of the others, yes.
    Senator Landrieu. OK.
    Those are my questions. Thank you. I'm going to submit the 
rest for the record.
    The Chairman. Thank you very much.
    Let me just try to put a little finer point on Dr. Zoback's 
testimony and as least as I understand it just to be clear. As 
I understand, your basic point is that you doubt that CCS, 
carbon capture and storage, can be a successful strategy for 
dealing with the long term effects of climate change. A main 
reason you doubt that is because of these small to moderate 
sized earthquakes that, not only do you have to have 3,500 of 
these projects like the one you've just described to us.
    But there are small to moderate size earthquakes that occur 
naturally, as I understand it, that will, as you put it, 
threaten the seal integrity of the formations that might be 
used for the CCS. Is that accurate?
    Mr. Zoback. That's exactly our point, Senator.
    The Chairman. Yes. Alright.
    Is this something you and fellow researcher expert that you 
mentioned have concluded on your own? Is this anything that 
the--any other group has looked at? Has the National Academy 
reviewed that set of recommendations or conclusions?
    Mr. Zoback. Basically the conclusions we've recently 
written about are essentially identical to the conclusions that 
the committee, chaired by Professor Hitzman, came to. So we're 
in complete concordance. They basically said----
    The Chairman. But their report, the one that we have before 
us today doesn't go as far as you're going with your 
conclusions about the problems with planning on CCS as a 
strategy for long term climate change mitigation.
    Mr. Zoback. That's true. They did not go that far. But in 
some ways they went further by pointing out the potential for 
large earthquakes because of the extremely large volumes to be 
injected.
    The question there is how good site characterization 
studies will be. We took what we thought was an approach by 
saying the site characterization will be so comprehensive that, 
you know, there will be no big faults. There will be no 
probability for a bigger earthquake. But it's the small faults 
that you can miss.
    So therefore, our statement would have been due to the 
large scale, large volumes, there's a high probability of 
something happening, probably something small to moderate in 
size. Their statement was a bit stronger on the hazard part of 
it. They said that in fact there was the potential, perhaps, of 
missing some of the bigger faults and a potential for a larger 
earthquake occurring.
    So philosophically I think we're 100 percent in agreement. 
It's a slight change in interpretation about what the hazard 
might be.
    The Chairman. Dr. Hitzman, let me just ask you.
    Did you--does your report deal with the issue of whether or 
not small earthquakes or small instances of induced seismicity 
might result in natural earthquakes being substantially more 
likely in certain areas? For example if you go to a place where 
there's a natural known fault and there's a real risk of an 
earthquake at some point, could you hasten the time of that 
earthquake or increase the likelihood of that natural major 
earthquake by doing the type of small injection activity that 
we're talking about here?
    Mr. Hitzman. That is addressed in the report. The basic 
answer is yes that many faults are near a critical state. So if 
we perturb them, manmade, we can trigger events. So the answer 
is yes.
    Is that something we routinely do? No. I mean site 
characterization, especially around areas of known faults we do 
today.
    So I don't see that as a particular large issue.
    The Chairman. So as long as we stay away from the known 
faults that are naturally there, we pretty much deal with that 
problem.
    Mr. Hitzman. Right. But what happens is there are faults we 
don't know about. That's where, certainly in the waste water 
injection, that's where we've had the problems. We found faults 
we didn't know existed.
    The Chairman. Senator Murkowski.
    Senator Murkowski. Thank you, Mr. Chairman.
    I want to follow up to the questioning that Senator 
Landrieu had about the various types of waste water injection. 
It's my understanding that there are 6 different classes of 
injection wells.
    One is municipal and industrial waste. We've got mineral 
solution, mining. We've got other things.
    So the question would be whether or not we think that any 
of these other well classifications. Whether or not they've 
been associated with any additional seismic activity, whether 
we've looked at that. Whether it's possible that they could.
    Then as a follow on as we see communities expanding and 
population going into certain areas, is it possible that we 
could see enhanced seismic activity just due to what we're 
contributing from the municipal and industrial waste? I don't 
know whether it's a significant enough volume or quantity to 
make a difference. Have you looked at that?
    Mr. Hitzman. Our committee specifically looked at Class Two 
wells with energy injection.
    Senator Murkowski. OK.
    Mr. Hitzman. So we didn't consider the others.
    But what I would say is it really makes no difference 
whether the fluid is produced by an energy or by another 
industry or just simply waste water. It's water being injected 
down.
    Senator Murkowski. It's the volumes that are the critical 
piece.
    Mr. Hitzman. Right. Right.
    So as we inject more and more volume into the subsurface, 
we probably will have more and more potential for seismic 
events.
    Senator Murkowski. OK. Alright.
    Ms. Petty, we've been quiet regarding geothermal here. I am 
a huge advocate of geothermal power and the resource itself. 
We've got, I think, some considerable opportunities in my 
State. We've also got some pretty impressive fault lines that 
run up there have had a history of earthquake activity.
    We've apparently managed to avoid any major issues. I think 
that that's great. But in listening to your testimony you seem 
to indicate that the risks associated with geothermal are 
perhaps more minimal.
    I guess a very generic question is whether or not you think 
the benefits then of geothermal outweigh any potential risk 
associated.
    Ms. Petty. I think that the main aspect of this, as Dr. 
Hitzman said, is that in geothermal we want to balance the 
injection and production so that we don't have a 
disproportionate amount of either. That way the pore pressure 
doesn't change. There have been some cases in geothermal fields 
where we didn't do that, where we took out more than we put 
back in.
    In those cases, especially when we started to put more in 
we've had increased amounts of seismicity. I think it's that 
balancing of injection and production that's kind of inherent 
to doing a good job of managing geothermal that makes me feel 
that we have less of an issue for potential large scale, 
induced seismicity, felt induced seismicity in geothermal.
    The cases where we are near large faults, I mean, in fact 
there are a number of geothermal fields that are near or 
actively injecting into faults. But because they add balance to 
the injection and production there hasn't been an issue.
    For EGS where we are creating a reservoir, we--a necessity 
when we start out, we inject more than we produce because we 
don't produce anything until we make the reservoir. That's when 
the risk is more clear to us. In that's where we need to have 
some kind of mitigation protocol. We have to have good site 
characterization, so that we can get that big resource.
    Senator Murkowski. It sounds like so much of this is, is we 
are learning. That's an important piece to recognize in all of 
this as well.
    Dr. Zoback, you mention that there are ways that we can 
manage the risk. You cited 4 different points.
    I mean, one, which is pretty obvious, is avoid the faults. 
So we need to know where we are and we need to better 
understand our geology. Pay attention to that I would think.
    But appreciating that we can manage risk is one thing. Is 
there any way to avoid it to the extent that you can tell 
people don't worry? We know and we understand what it is that 
we have to do to balance this. There should be no cause for 
concern.
    Are we to that point?
    Mr. Zoback. In some cases. For example thorough site 
characterization is a basis for assuring the public that you've 
done due diligence before you start.
    Monitoring with enhanced seismic networks if you think 
you're in an area where something might happen. You know, 
you're on top of it. That's another issue that should assure 
the public.
    But something else is happening that should be pointed out 
with respect to the shale gas development and waste water 
injection problem. That is in the Northeastern U.S. which is, 
you know, an area of active development with the Marcellus 
shale is being exploited. There are really no good places to 
inject the waste water.
    So what's happening is that industry has largely started to 
recycle the waste water. So the water that comes back from 
hydraulic fracturing is now being reused in subsequent 
hydraulic fracturing operations. That's beneficial for 
everyone.
    You use less water. So the water resources are protected. 
You basically put the contaminated water, which was 
contaminated by its interaction with the shale to begin with. 
You put it back into the shale.
    So the more you can recycle these flow back waters, the 
smaller you make the problem. In the Northeastern U.S. this is 
now standard practice. In other areas, if there's difficulty 
finding, you know, safe injectionsites, that practice can be 
extended to other parts of the country.
    Senator Murkowski. We were in West Virginia this weekend 
looking at--we were at the Marcellus. They were speaking 
exactly to that process of the recycling and how that all plays 
into it. Again a recognition that we're learning a little bit 
more.
    Did you learn anything from this report that you found 
surprising?
    Mr. Zoback. It was really nice to see that the information 
compiled, as it was. I was aware of the general issues, but 
they did a terrific job of pulling together information on a 
global basis and of course, with the United States getting 
particular emphasis.
    The other thing I really appreciated out of the report was 
that it points to the need for data. So often we're asked, 
well, was that earthquake triggered or not. You don't have a 
baseline to make an answer to that question.
    Whether it's a seismic baseline and you're not aware of 
what the seismicity was prior to a larger event occurring or 
the pore pressure or the stress or the pre-existing faults. In 
both the Youngstown and Guy, Arkansas cases scientists have 
come forward after the fact and said, oh yeah, there was an 
active fault right there that was being injected into. Had that 
data been available prior to the injection neither incident 
would have occurred.
    So, you know, in some ways, as the report illustrates in 
case after case we have a good conceptual understanding of what 
the issues are but we rarely have the data in order to use that 
conceptual understanding to be definitive about, you know, 
what's happened and how to prevent things from happening in the 
future. So it's a data issue as much as anything else.
    Senator Murkowski. Thank you all. I appreciate your 
testimony this morning.
    Thank you, Mr. Chairman.
    The Chairman. Thank you.
    Let me ask about a bill. Senator Murkowski referred to one 
of the bills that's been reported out of our committee, S. 699, 
that provides--it proposes to provide some liability protection 
for CCS projects. The idea of that or the general thrust of it 
is to say that for the first ten large demonstrations of CCS 
there would be some liability protection provided if DOE could 
determine that there's adequate measuring and monitoring and 
testing to verify that the carbon dioxide that is injected into 
the injection zone is not escaping or migrating and is not 
endangering underground drinking water sources.
    The idea of the legislation and then of course the bill 
tries to provide a long term stewardship for these 
demonstration projects, these first 10. I guess that I'd ask 
Dr. Hitzman. Is there anything in your report or in the work 
that your committee did that would tell us whether it makes 
sense to proceed with these kinds of large demonstration 
projects or to have encouragement to industry to proceed with 
these or not?
    I mean, is this something that is a waste of effort or is 
it something that would make some sense to help us understand 
whether or not this is an avenue that's going to be beneficial?
    Mr. Hitzman. I think what the report says is that we also 
see the potential benefits of doing CCS. But that we really 
need to understand it better at the scales that are being 
projected. So I'm not sure exactly how large, how many--what 
the volume is in these ten demonstration projects over the long 
term.
    But we recommend that the DOE continue with its research, 
probably use some of the research it's doing now and focus it a 
little more on this particular issue so it can be better 
understood. That right now, we need the data. We can't answer 
your question directly.
    The Chairman. OK.
    Dr. Zoback, did you have thoughts as to whether it makes 
sense for the Department of Energy and the Federal Government 
to be encouraging some of these large scale demonstration 
projects through this kind of legislation or do you think it's 
such a non-starter as that we really should look elsewhere to 
solve the long term climate change issue.
    Mr. Zoback. The paper that we, my colleague and I, just 
published on this topic is published as a perspective piece. It 
really is our perspective that because of these potential 
problems one has to consider this, the strategy of large scale 
CCS with these issues in mind. So what we're trying to do--and 
by the way, the paper was published yesterday. So there's going 
to be a lot of reaction to it without question.
    What we're trying to do is just change the dialog and ask 
people to consider this question not just in the context of the 
scale and the cost which have been raised by many people in the 
past. They are very real issues. But also in the context if 10 
or 20 years from now one of these moderate sized earthquakes 
occur in one of the repositories what is that going to mean for 
this strategy that we've, you know, we've embarked on.
    So this has to be thought through very carefully. I'm not 
familiar with the legislation you referred to. So I'd rather 
not comment on it.
    But we're just trying to change the dialog and broaden 
people's perspective just as the case that triggered seismicity 
is not considered in the licensing requirements for a Type Two 
waste water injection well. Perhaps it should be, at least in 
certain parts of the country. Triggered seismicity should 
certainly be a strong consideration as we look at CCS in a 
research mode in the future.
    The Chairman. But your concern is triggered seismicity. But 
you're also--your concern is natural seismicity. You're 
basically saying there are natural, small and medium sized 
earthquakes that may thwart our ability to use CCS at large 
scale to solve climate change problems long term.
    Mr. Zoback. That's true, Senator. We're--but by raising the 
pore pressure, you know, the probability of something happening 
goes up because you are basically advancing the time at which a 
natural event would have occurred anyway. So in a given area 
natural earthquakes occur but they might be so infrequent that 
you would assume that during the lifetime of the repository 
there's no possibility of an event occurring.
    But by injecting fluid we sort of bring the faults closer 
to failure and therefore enhance that probability.
    The Chairman. Senator Murkowski, did you have additional 
questions?
    Thank you all very much. I think this has been very useful.
    Again, Dr. Hitzman, thank you for all the work you did on 
this report and your entire committee.
    That will conclude our hearing.
    [Whereupon, at 11:18 a.m. the hearing was adjourned.]
                                APPENDIX

                   Responses to Additional Questions

                              ----------                              

   Responses of Murray W. Hitzman to Questions From Senator Bingaman
    Question 1. Dr. Zoback has testified that the risk of venting 
stored carbon dioxide from small, induced seismic events is a primary 
concern and obstacle to the scaling up of CCS technologies to play a 
significant role in mitigating global greenhouse gas emissions to the 
atmosphere. Do you agree with this assessment?
    Answer. The statement of task for the study did not examine include 
consideration of the escape of carbon dioxide from CCS projects, thus 
we are not in a position to comment on this aspect of induced 
seismicity.
    Question 2. The NAS study we just heard about indicates that there 
have been relatively few induced seismic events that are directly 
attributable to the energy technologies considered here. At the same 
time, Dr. Leith's testimony shows a sharp increase in the number of 
mid-continent earthquakes that USGS has measured over the past decade.
    Question 2a. Is there something else going on that could be causing 
this trend in earthquakes?
    Answer. The data Dr. Leith referred to in his testimony became 
available at the end of the NRC study and was not available in a peer-
reviewed form. Hence, we were unable to examine it in detail. There 
could be a number of reasons for the seismicity to have apparently 
increased. Deep well disposal of waste water associated with energy 
development is one possibility. Another is a natural increase in 
seismicity. Finally, the apparent increase in number of events could be 
due to changes in the monitoring technologies employed over the past 
several years.
    Question 2b. Is this a measurement issue, or is it just that more 
work needs to be done to figure out what caused these earthquakes?
    Answer. As noted above, it could be a measurement issue. Certainly 
more work is required to better understand these seismic events.
   Responses of Murray W. Hitzman to Questions From Senator Murkowski
    Question 1. To the extent that wastewater injection wells are 
geologically unavailable in certain Eastern US areas, might those areas 
bear a correspondingly remote risk of induced seismicity from natural 
gas development?
    Answer. If the question is if waste water injection wells are not 
utilized will the seismic risks be decreased the answer is yes. 
However, fluids from energy development will need to be managed in some 
manner.
    Question 2. The NRC report indicates that the Federal and State 
Underground Injection Control (UIC) Programs ``do[es] not address the 
issue of seismicity induced by underground injection.'' At the same 
time, the current UIC program does require the injection well operator 
to perform a site characterization, including identifying the risks 
associated with nearby faults if any are located. Furthermore, several 
states (including Arkansas, Colorado, Ohio, and West Virginia,) are 
currently modifying their UIC Programs to specifically address 
seismicity. To this extent, might those state regimes reflect any of 
the proposed actions as noted in the report?
    Answer. The NRC report states ``the Safe Drinking Water Act . . . 
does not specifically address the issue of seismicity induced by 
underground injection. (page 106)'' However, individual states have the 
authority to promulgate rules above and beyond the requirements of the 
SDWA including requirements such as providing additional information 
concerning induced seismicity as part of the permitting process. Our 
report (page 119) specifically notes the states of Colorado and 
Arkansas have adopted additional permitting regulations concerning 
induced seismicity in addition to the regulatory framework put forth in 
the SDWA. The additional information required by the state of Colorado 
closely parallels portions of the ``Hazard Assessment'' protocol 
recommended in our report on page 146. Our report also notes on page 
106 ``UIC regulations requiring information on locating and describing 
faults in the area of a proposed disposal well are concerned with 
containment of the injected fluid, not the possibility of induced 
seismicity.''
    Question 3. The report establishes the ``felt at surface'' 
threshold as a magnitude 2.0 seismic event. However, USGS documents 
state that a magnitude 2.0 to 2.9 is generally not felt, but might be 
recorded, while for the general population a magnitude 3.0 to 3.9 is 
more likely to be ``felt.'' As also noted, a seismic event typically 
does not cause damage until its magnitude falls in the range of 4.0 to 
4.9, and the report indicates that the purpose of implementing a risk 
management protocol is to prevent the occurrence of damaging events. 
Are the report's proposed actions targeted at such a risk management 
protocol or do they go further to seek to address any induced 
seismicity which might be recorded?
    Answer. While seismic events in the 2.0 range are commonly not 
felt, particularly if they occur deep within the Earth's crust, the NRC 
committee met with residents living in the area of The Geysers where 
events in this range are shallow and are routinely felt. Damage from a 
seismic event depends on the location of the event relative to the 
structures being considered, the construction of such structures, and 
their contents. The NRC committee identified magnitude 2.0 since this 
is the smallest seismic event that can usually be felt by humans, even 
for shallow events caused by humans. The committee certainly is 
suggesting a risk protocol that is practical and widely applicable, not 
one for events that pose no risk. We would note that we are not 
disagreeing with the USGS documents, but feel the difference in wording 
has to do with the preciseness of the threshold of what may be felt.
    Question 4. Of the corresponding wells drilled for each of the 
following energy technologies in the U.S., please provide what 
percentage have been proven to induce seismicity:

          A) Enhanced oil recovery
          B) Wastewater injection wells
          C) Geothermal
          D) Hydraulic fracturing

    Answer. The committee could not find reliable statistics on the 
percentage of wells that have, or might have, induced felt seismicity 
(greater than M 2.0) for various energy technologies. Developing a 
reliable database of the numbers and characteristics of wells, and of 
the incidences of induced seismicity, as recommended in our report, 
will help with the understanding of the percentages associated with 
induced seismicity.
    However, based upon the available data from peer-reviewed resources 
the committee identified and examined, neither enhanced oil recovery 
nor hydraulic fracturing have to date have been proven to have induced 
felt seismic events in the United States.
    Regarding geothermal energy, although some of the events in our 
report's database were clearly caused by injection to generate 
geothermal energy (for example at the Geysers and in the Coso 
geothermal field), geothermal wells tend to be drilled in areas that 
are often seismically active, making `proof' of the tie to fluid 
injection difficult.
    Our report suggests that felt earthquakes at about 8 locations in 
the US over a period of about 40 years have been reasonably proven to 
be linked to wastewater injection. We know only the approximate number 
of wells today (30,000); some of the older wells that caused felt 
events are no longer in operation. An approximate estimate of the 
fraction of wastewater wells that have induced felt earthquakes is 
therefore 8/30,000, which is about 3/100 of 1%.
    Question 5. At the hearing, it was not clear how many of the 
various UIC wells of various classes were associated with oil and gas 
development (as opposed to municipal waste, etc.). Can you provide the 
committee with the breakdown of the various UIC well types and 
percentages relative to the total number of wells?
    Answer. The committee examined in detail only Class II wells, with 
some mention of Class V and Class VI (CCS) wells. The only Class VI 
wells currently in operation are those associated with two carbon 
sequestration test sites supported by the Department of Energy. Class 
II wells, of which there are approximately 151,000 currently permitted 
in the United States, are all used for the injection of fluids 
associated with oil and gas operations. Of that total of 151,000, 
approximately 30,000 (20%) are for waste water disposal (from oil and 
gas development), approximately 108,000 (71%) are for secondary oil 
and gas recovery (waterflooding), and approximately 13,000 (9%) are 
for tertiary recovery (enhanced oil recovery). Class V wells are the 
most numerous, accounting for almost 79 percent of the total number of 
UIC wells; wells used for fluid injection related to geothermal energy 
fall within this well class. However, only 239 wells in the United 
States among approximately 400,000-650,000 Class V wells permitted in 
the country are for geothermal energy. The committee did not examine 
the other kinds of wells (which include storm water drainage wells, 
septic system leach fields, etc.) in this study so cannot provide a 
breakdown of the numbers of these kinds of wells.
                                 ______
                                 
      Response of Mark D. Zoback to Question From Senator Bingaman
    Question 1. Your testimony noted that offshore formations similar 
to the one utilized by the Sleipner project in Norway and also depleted 
oil and gas reservoirs could potentially be suitable for long-term 
storage of high volumes of carbon dioxide. The Department of Energy 
indicates there may be as much as 7.5 trillion tons of CO2 
storage capacity in offshore formations in the Gulf Coast that are 
similar to the Sleipner project in Norway. The most recent estimates 
from the National Energy Technology Laboratory indicate that there may 
be as much as 20 billion tons of CO2 storage capacity in 
depleted oil and gas reservoirs.
    Question 1a. Could you please comment on these assessments of 
storage capacity and their suitability for the long-term storage of 
high volumes of carbon dioxide?
    Question 1b. Could you provide an estimate of how much storage is 
available in the types of formations that you described as having 
suitable characteristics for such long-term storage?
    Answer. As we noted in our PNAS paper on the potential of triggered 
seismicity associated with CO2 storage, there are a large 
number of formations in the Gulf Coast that have appropriate 
characteristics for long term CO2 storage. In other words, 
they are porous, permeable, weakly-cemented, laterally extensive, have 
adequate cap rocks and seals, etc. I am not familiar with the screening 
criterion used by the Dept. of Energy in their assessment of 7.5 
trillion tons of CO2 storage capacity in these formations. 
If their criterion considered all of the characteristics enumerated 
above, it should be straightforward to calculate the rates at which 
CO2 could be injected without generating excess pore 
pressure could accommodate the enormous volumes of CO2 
generated in the U.S. each year. Obviously, transport of large 
quantities of  from thousands of point sources throughout 
the U.S. to the Gulf Coast would be a formidable operational challenge. 
Nonetheless, utilizing appropriate geologic formations in the Gulf 
Coast is a far more attractive strategy than utilization of non-ideal 
formations (from the perspective of possible earthquake triggering) 
that are located more closely to CO2 sources.
    With respect to the National Energy Technology Laboratory's 
estimate that 20 billion tons of CO2 could be stored in 
depleted oil and gas reservoirs, it is important to recognize that this 
does not represent very much capacity. Coal burning power plants in the 
U.S. alone generate about 2 billion tons of CO2 each year so 
that depleted oil and gas reservoirs could accommodate emissions from 
coal burning plants for only 10 years. Another consideration is that 
successful long-term storage of CO2 in depleted reservoirs 
could be compromised by leakage through the cemented annulus of wells 
or via damaged well casings. Both are common occurrences in old wells. 
In addition, it is important to assure that oil field operations did 
not affect the natural geologic seals of the hydrocarbon reservoir. 
There are a variety of mechanisms could compromise the reservoir's seal 
such as depletion-induced faulting or hydraulic fracturing, either when 
the well was first drilled or during subsequent water flooding 
operations.
    I have not carried out an assessment of the CO2 storage 
capacity of the geologic formations I would classify as being ideal for 
sequestration. Thus, I cannot respond to question 1b.
    Responses of Mark D. Zoback to Questions From Senator Murkowski
    Question 1. To the extent that wastewater injection wells are 
geologically unavailable in certain Eastern US areas, might those areas 
bear a correspondingly remote risk of induced seismicity from natural 
gas development?
    Answer. It is true that there is a remote risk of triggering 
seismicity associated with multistage hydraulic fracturing in 
horizontal wells, the typical technique used to produce natural gas 
from shale formations. Any given hydraulic fracturing operation 
involves pressurization of small volumes of rock (typically a few 
hundred feet along the length of the wellbore) for short periods of 
time (typically about two hours). Hence, the probability of the 
pressurization affecting faults that might induce earthquakes large 
enough to be felt at the surface is extremely low. I fully agree with 
the conclusion of the NRC report that this is the principal reason why 
hundreds of thousands of hydraulic fracturing operations to develop gas 
from shale in the U.S. have not produced any confirmed cases of 
triggered seismicity. Globally, there has only been one confirmed case 
in which hydraulic fracturing associated with shale gas development has 
triggered one very small earthquakes big enough to be felt at the 
surface. Considering the extremely small number of triggered 
earthquakes with hundreds of thousands of hydraulic fracturing 
operations clearly demonstrates that the risk associated with shale gas 
development is extremely low.
    Question 2. The NRC report indicates that the Federal and State 
Underground Injection Control (UIC) Programs ``do[es] not address the 
issue of seismicity induced by underground injection.'' At the same 
time, the current UIC program does require the injection well operator 
to perform a site characterization, including identifying the risks 
associated with nearby faults if any are located. Furthermore, several 
states (including Arkansas, Colorado, Ohio, and West Virginia,) are 
currently modifying their UIC Programs to specifically address 
seismicity. To this extent, might those state regimes reflect any of 
the proposed actions as noted in the report?
    Answer. It is good to learn that several states are modifying their 
UIC Programs to address the potential for triggered seismicity. If this 
has been in response to the NRC report, this is indeed a welcome 
development.
                                 ______
                                 
     Responses of William Leith to Questions From Senator Bingaman
    Question 1. Dr. Zoback has testified that the risk of venting 
stored carbon dioxide from small, induced seismic events is a primary 
concern and obstacle to the scaling up of CCS technologies to play a 
significant role in mitigating global greenhouse gas emissions to the 
atmosphere. Do you agree with this assessment?
    Answer. Dr. Zoback's study identified the need to carefully study 
any prospective CCS projects and to evaluate potential risks associated 
with particular projects. We agree that induced earthquakes could be a 
significant risk to the efficacy of large-scale CCS and that this 
hazard needs to be carefully studied and better understood. Although 
injection of CO2 into depleted oil and gas reservoirs (for 
example, as used in secondary oil recovery) may pose a low risk for 
induced seismicity, such is not the case during injection of 
CO2 into normally pressurized, undepleted aquifers. For 
injection in undepleted reservoirs, the geologic sequestration of 
CO2 is probably not significantly different from other 
large-volume liquid-injection projects, such as wastewater disposal at 
depth, for which there are numerous case histories involving 
earthquakes large enough to be of concern to the public. One of the 
early case histories concerned the injection of 625,000 cubic meters of 
wastewater at the Rocky Mountain Arsenal (RMA) well in the mid-1960s, 
which induced earthquakes of about magnitude 5 and caused damage to 
structures in the Denver, CO, area.
    Over the next three years, a DOE-sponsored demonstration project in 
Decatur, IL, will inject 1 million tons-about 1.4 million cubic meters 
of CO2- into an undepleted brine aquifer within the Mt. 
Simon sandstone at a depth of about 2 km. Injection at the Decatur well 
began in November 2011. Although the induced earthquakes at this site 
have been tiny as of July 2012, it is much too early to know what the 
seismic response will be as the injection grows; the total planned 
volume of injected CO2 at Decatur is more than double what 
was injected at the RMA. If the induced earthquake pattern at Decatur 
turns out to be similar to that at RMA, then some of the larger induced 
earthquakes that would occur at the site could indeed pose threats to 
the integrity of the capping seals. It is also possible that high 
pressures generated within the Mt. Simon sandstone could be 
communicated to ``hidden'' faults within the underlying granite 
basement. Although such faults have not been seen in the seismic data 
collected at Decatur so far, it is notoriously difficult to image 
faults in deep granitic rocks. Thus, a prudent approach would be to 
assume that there could be an earthquake risk to nearby communities 
during this project.
    To assess these seismic hazards, it is necessary to monitor induced 
earthquakes at each CCS pilot project with a seismic network designed 
to locate events precisely in three dimensions and thereby determine 
the exact nature of the seismic source. Microearthquake locations 
enabled by such a network would allow us to identify previously unknown 
faults within the underlying basement, as well as determine the maximum 
likely fault slip associated with these and other faults, including 
those located near the sealing formations. Other types of field and 
laboratory research will be needed to achieve a comprehensive 
understanding of the risk to reservoir seals from earthquake slip in 
various geological settings.
    Question 2. As USGS considers the amount of available storage for 
CCS, is the possibility of leakage from small seismic events something 
that is factored in?
    Answer. The 2007 Energy Independence and Security Act (Public Law 
110-140, section 711) authorized the USGS to conduct a national 
assessment of geologic storage resources for carbon dioxide 
(CO2). The methodology that was developed for the national 
assessment (Brennan and others, 2010, http://pubs.usgs.gov/of/2010/
1127/) addresses the geographical extent, the capacity, injectivity 
(permeability), and the risk associated with potential storage 
formations. We evaluate the risk of a potential formation by providing 
maps of existing well penetrations which, in some cases, may be 
potential CO2 leakage pathways (for example well penetration 
maps see Covault and others, 2012, http://pubs.usgs.gov/of/2012/1024/a/
). The USGS methodology also incorporates the Environmental Protection 
Agency (EPA) guidelines to prevent CO2 leakage to the 
surface and CO2 contamination of underground sources of 
drinking water (USDW) and overlying aquifers. EPA's guidelines are: (1) 
a regional, well defined sealing unit to be present above each storage 
assessment unit, and (2) only assessing storage assessment units that 
have formation waters that are greater than 10,000 parts per million 
total dissolved solids. The risk of induced seismicity associated with 
a particular CO2 storage project depends on local storage 
reservoir fluid pressure management and CO2 injection rates 
and volumes, and is, therefore, an engineering problem that is not 
specifically evaluated in the current USGS CO2 storage 
assessment efforts. We do, however, note that a potential storage 
formation may be located in a region of the country where natural 
seismic risks are more likely. We are incorporating a discussion of the 
proximity of a potential storage formation to seismically active areas 
in the geologic framework reports for each assessed area that will be 
published during the coming year.
    Question 3. Dr. Zoback's testimony noted that offshore formations 
similar to the one utilized by the Sleipner project in Norway and also 
depleted oil and gas reservoirs could potentially be suitable for long-
term storage of high volumes of carbon dioxide. The Department of 
Energy indicates there may be as much as 7.5 trillion tons of 
CO2 storage capacity in offshore formations in the Gulf 
Coast that are similar to the Sleipner project in Norway. The most 
recent estimates from the National Energy Technology Laboratory 
indicate that there may be as much as 20 billion tons of CO2 
storage capacity in depleted oil and gas reservoirs.
    Question 3a. Could you please comment on these assessments of 
storage capacity and their suitability for the long-term storage of 
high volumes of carbon dioxide?
    Question 3b. Could you provide an estimate of how much storage is 
available in the types of formations that Dr. Zoback has described as 
having suitable characteristics for such long-term storage?
    Answer a. The North American Carbon Storage Atlas (2012, available 
at: http://www.netl.doe.gov/technologies/carbon_seq/global/nacap.html), 
published jointly by the Department of Energy and representative 
agencies from the governments of Canada and Mexico, indicates that 
within the Atlantic, Gulf of Mexico, and Pacific offshore regions of 
the United States, there is an estimated range of 467 billion to 6.4 
trillion metric tons of potential CO2 storage capacity in 
saline formations. The North American Storage Atlas also reports that 
oil and gas reservoir CO2 storage resources for the United 
States (onshore and offshore) are approximately 124 billion metric 
tons. In addition, a report by Kuuskraa and others (2011, http://
www.netl.doe.gov/energy-analyses/pubs/storing percent20co2 percent20w 
percent20eor_final.pdf), that was prepared for the National Energy 
Technology Laboratory, indicates that nearly 20 billion metric tons of 
CO2 may be needed to economically produce oil using ``Next 
Generation'' enhanced-oil-recovery techniques utilizing a mixture of 
naturally occurring CO2 produced from CO2-rich 
underground reservoirs and CO2 from anthropogenic sources. 
The resource numbers reported by the North American Carbon Storage 
Atlas (2012), the Carbon Sequestration Atlas of the United States and 
Canada (NETL, 2010, http://www.netl.doe.gov/technologies/carbon_seq/
natcarb/index.html), and Kuuskraa and others (2011) are general 
estimates of potential geologic CO2 storage resources in 
various regions of North America and the United States.
    The USGS is currently working on a comprehensive assessment of 
onshore areas and State waters that will identify and evaluate the 
Nation's potential CO2 storage resources. Data used in the 
previous DOE assessments and data provided by State geological surveys 
are being integrated with USGS data to conduct these assessments. The 
USGS typically does not assess Federal offshore U.S. resources and 
refers to or works with the Bureau of Ocean Energy Management (BOEM) 
when evaluating offshore resources. By 2013, the USGS Geologic 
CO2 Sequestration Assessment Project will have geologically 
characterized and assessed more than 200 potential storage formations 
in 37 basins across the United States. This assessment will be the most 
comprehensive accounting of the Nation's CO2 storage 
potential ever completed, and provide quantitative, probabilistic 
estimates of resource storage potential. A summary report is in 
preparation that will provide the storage assessment results for the 
Nation. In addition, the Geologic CO2 Sequestration Project 
is building an assessment methodology and associated engineering 
database that can be used for a detailed national assessment of 
recoverable hydrocarbon resources associated with CO2 
injection and sequestration. USGS assessments are impartial, robust, 
statistically sound, and widely cited in the scientific literature and 
public media.
    Answer b. The USGS assessment of CO2 storage capacities 
of onshore areas and State waters of the United States is scheduled to 
be completed in 2013. We do not have resource estimates available at 
this time. As mentioned in the answer for question 2 above, the risk of 
induced seismicity associated with a particular CO2 storage 
project depends on local storage reservoir fluid pressure management 
and CO2 injection rates and volumes, and is, therefore, a 
scientific and engineering problem that is not specifically evaluated 
in the current USGS CO2 storage assessment. The scope of 
research needed to better predict seismic risk in particular geologic 
settings is discussed further in the answer to question 1. In order to 
provide resource estimates for formations that are not likely to be 
prone to induced seismicity, an additional set of screening geologic 
and engineering criteria will need to be developed and applied to the 
assessment results generated by the current USGS Geologic 
CO2 Sequestration Assessment Project.
    Question 4. Is USGS doing, or planning to do work to better 
understand the risks of induced seismicity due to large-scale CCS as 
indicated in the report? Are there efforts at other agencies or 
national labs?
    Answer. The USGS is currently proposing to monitor induced 
seismicity at one or more DOE-funded CCS pilot projects, and we have 
been in contact with the operators of two such projects: one at 
Decatur, Illinois, and the other at Kevin Dome, northern Montana. 
Although no agreements have been reached so far, the USGS, as an 
objective science agency, is in a unique position to provide scientific 
knowledge needed to better understand and mitigate the potential 
seismic risk associated with CCS. In so doing, it is critical that 
these data and analyses be maintained in the public domain, to be 
amenable to full scientific peer review and to maintain public trust.
    The USGS recently purchased seismic recording equipment sufficient 
for a ten-station monitoring network that includes three seismometers 
that will record down boreholes about 500 feet deep. In the lower-noise 
environment at the bottom of these boreholes, we anticipate that the 
magnitude threshold for earthquake detection will be reduced 
considerably.
    The DOE-funded National Laboratories have conducted earthquake 
monitoring at CCS sites in Algeria and Australia, and perhaps other 
sites. In addition, the National Laboratories maintain an active and 
highly visible program in monitoring induced seismicity associated with 
Enhanced Geothermal Systems demonstration projects at several locations 
in the United States.
    The President's budget request for fiscal year 2013 includes, as 
part of the hydraulic fracturing initiative, a proposed $1.1 million 
increase to the Earthquake Hazards Program for work assessing the 
factors controlling the triggering of earthquakes due to fluid 
injection activities, developing a method to forecast the magnitude-
frequency distributions of induced earthquakes including the maximum-
magnitude earthquakes resulting from a specified fluid injection 
operation, and accounting in National Seismic Hazard Maps for the 
additional hazards due to fluid disposal-induced earthquakes.
    Question 5. The NAS study we heard about indicates that there have 
been relatively few induced seismic events that are directly 
attributable to the energy technologies considered here. At the same 
time, your testimony shows a sharp increase in the number of mid-
continent earthquakes that USGS has measured over the past decade.
    Question 5a. Is there something else going on that could be causing 
this trend in earthquakes?
    Question 5b. Is this a measurement issue, or is it just that more 
work needs to be done to figure out what caused these earthquakes?
    Answer a. USGS believes that the increase in the number of 
magnitude 3 and larger earthquakes in the U.S. midcontinent is most 
probably caused by increased wastewater injection activities. The 
increase is most pronounced in Arkansas, along the Colorado-New Mexico 
border, and in Oklahoma. Earthquakes have also been noted in Texas, 
Ohio, and West Virginia, where they are otherwise uncommon. Research 
published since the NAS report was written demonstrates that the 
increase in earthquake activity in Arkansas is due to injection of 
wastewater related to shale gas development and production: http://
srl.geoscienceworld.org/content/83/2/250. Studies recently completed by 
the USGS show that the earthquakes along the Colorado-New Mexico border 
are due to wastewater injection from coal-bed methane production in the 
Raton Basin. Studies to identify the underlying cause or causes of the 
increase in seismicity in Oklahoma are underway.
    Answer b. USGS is certain that the rate change discovered is not a 
measurement issue. Three lines of evidence support this conclusion. 
First, earthquakes with magnitudes of 3 and above (those used to detect 
the rate change) have been uniformly detected through the midcontinent 
since the 1970s by the USGS. Second, while improvements in seismic 
instrumentation and installation of additional seismic stations have 
improved earthquake location accuracy, the algorithms for computing 
magnitude have remained unchanged. Third, both the USGS catalog and the 
catalog of the Oklahoma Geological Survey independently document the 
increase in activity that began in that state in 2009.
    To understand the factors that have led to the increased rate of 
induced earthquakes in the central and eastern United States, more work 
is clearly needed. Site-specific investigations will be required to 
identify the underlying causes and improve our understanding so that 
the risk of induced earthquakes can be managed in the future.