CCST has released an independent report that reviews well stimulation technologies, including
hydraulic fracturing, used in on-shore oil reservoirs in the state of California. This study was
commissioned by the Federal Bureau of Land Management (BLM) and will inform BLM's oil and gas
policies in California.
The findings of this CCST report describe current well stimulation activities in California, how,
when and where they are currently applied, where they might be applied in the future and how this
practice differs from other states. The report assesses information relevant to the potential future
use of these technologies, and how they might or might not directly impact water supply, water
quality, air quality, greenhouse gas emissions, seismicity, ecology, traffic and noise.
This independent scientific assessment of the available facts presents information for public use
and will help to guide regulation and policymaking. A second expanded report on the same topic is
currently in preparation for the California Natural Resources Agency in response to Senate Bill 4.
"Responsible decision making requires good science to balance economic potential with environmental
concerns," said CCST Executive Director, Dr. Susan Hackwood. "This report provides the most
objective, up-to-date, peer-reviewed assessment available to inform thoughtful policy making in
California, while also characterizing issues that require further study."
Lawrence Berkeley National Laboratory (Berkeley Lab), with help from the Pacific Institute,
developed the report findings under the guidance of a steering committee of experts chartered by
CCST. The steering committee, chaired by Dr. Jane C. S. Long, consisted of 12 subject-matter
experts drawn from many of the major research institutes in the state as well as experts from other
states with experience in well stimulation technology. "The people of California should know that
the scientists conducting this study brought a wide variety of expertise, extensive experience and
open minds to this assessment," Dr. Long said. "We conducted a careful and fact-based review that
achieved consensus on all conclusions." Dr. Jens Birkholzer, project leader for Berkeley Lab added,
"Participating scientists at the lab have been working to understand and ameliorate the impacts of
hydraulic fracturing for some time and the lab was pleased this expertise could be of service to BLM
and the state."
Commissioned in September 2013 by BLM, the independent report compiles existing data and literature
about the nature of well stimulation in California. The report arrives at 11 main conclusions. Key
among them are:
- Well stimulation in California is different than in other states. Available data suggest that
present-day well stimulation practices in California are different from other states such as Texas
and North Dakota primarily due to differences in the geology of the petroleum reservoirs.
Information from well records indicates that hydraulic fracturing has been the main type of well
stimulation applied in California to date and is performed on an estimated average of 100 to 150
wells per month, which is a modest level of activity compared to about 2,900 per month in the U.S.
as a whole reported by FracFocus. Generally, hydraulic fracturing in California tends to be
performed in shallower wells that are vertical as opposed to horizontal; requires much less water;
but uses fluids with more concentrated chemicals than hydraulic fracturing in other states.
Consequently, the experiences with hydraulic fracturing in other states do not necessarily apply to
current hydraulic fracturing in California.
- The most likely scenario for future oil recovery using hydraulic fracturing is expanded
production in and near existing oil fields in the San Joaquin Basin in a manner quite similar to the
production practices of today. Existing and likely future production in California takes place in
reservoirs that contain oil that has migrated from the rocks where it was formed ("source rocks") to
relatively near surface reservoirs where it can be produced. Over 85% of all well stimulation
applications in California take place in four fields of the San Joaquin Valley in reservoirs that
rely on hydraulic fracturing to enable production. It is highly likely that expanded production in
similar reservoirs in the San Joaquin Valley would also use this technology. Current production in
the Los Angeles Basin does not depend heavily on well stimulation and similar future production
could likely occur without these technologies.
- Recent reports from the Energy Information Agency (EIA) have indicated there may be a new class
of very deep unconventional reservoirs in the source rocks themselves, especially in the Monterey
Formation. The 2011 EIA report suggested 15-billion barrels of recoverable oil in these source
rocks but a subsequent 2014 correction by EIA reduced the estimate to 0.6 billion barrels.
Recovering these resources would certainly require well stimulation. However, Berkeley Lab
investigators found no reports of successful production from these deep source rocks and had
questions about the EIA estimation methodology. The study's review of the two resource projections
from deep source rocks in the Monterey Formation developed by EIA concluded that both these
estimates are highly uncertain.
- Current hydraulic fracturing operations in California require a small fraction of statewide
water use. In California a hydraulic fracturing operation can consume between 130,000 to 210,000
gallons of water per well on average, compared to about 4 million gallons per well used on average
in the Eagle Ford Formation in Texas. The study estimates that California operators conduct 100 to
150 well stimulations per month, which currently requires about 150 to 400 million gallons
(450-1,200 acre-feet) of water per year. Even with the relatively low water use of California
operations, hydraulic fracturing can contribute to local constraints on water availability given the
extreme drought in the state.
- There are no publicly reported instances of potable water contamination from subsurface
releases in California. However, more than half of the stimulated oil wells in California have
shallow depth (less than 2,000 feet). Shallow hydraulic fracturing poses a potential risk for
groundwater if usable aquifers are nearby. Some shallow hydraulic fracturing occurs where
groundwater is highly saline, or non-existent. However, investigators could not determine the
groundwater quality near many hydraulic fracturing operations and found that existing data was
insufficient to evaluate the extent to which contamination may have occurred. California needs to
develop an accurate understanding about the location, depth and quality of groundwater in oil- and
gas-producing regions in order to evaluate the risk of well stimulation to groundwater.
- The toxicity of chemicals used in hydraulic fracturing fluids warrants further review now that
SB 4 requires disclosure. Based on the voluntary database FracFocus, most of the chemicals used in
California well stimulations are not considered to be highly toxic. However, a few of these
chemicals, especially the biocides and corrosion inhibitors, are acutely toxic to mammals. No
information could be found about the toxicity of about a third of the chemicals and few of the
chemicals have been evaluated to see if animals or plants would be harmed by chronic exposure.
Mandatory disclosure should improve our understanding, as previous data acquired from FracFocus does
not consistently disclose all chemicals and may not always be complete or accurate.
- Some chemicals used for hydraulic fracturing may become incorporated in the water that is
produced along with the oil ("produced water"). In some cases, operators dilute produced water with
fresh water for use in agriculture and some produced water is pumped into unlined pits where it
could seep into the groundwater. Current practice and testing requirements do not necessarily
protect against adding produced water contaminated with hydraulic fracturing fluid to water used in
- Well stimulation technologies, as currently practiced in California, do not result in a
significant increase in seismic hazard. The pressure increases from hydraulic fracturing are too
small and too short in duration to be able to produce a felt, let alone damaging, earthquake. In
California, only one minor, anomalous earthquake (which occurred in 1991) has been linked to
hydraulic fracturing to date. In contrast, disposal of water produced from oil and gas operations
into deep injection wells has caused felt seismic events in several states. Expanded oil production
for any reason, including expanded use of hydraulic fracturing, would lead to increased volumes of
produced water, which, if injected underground could increase seismic hazards.
- Overall, in California, for industry practice of today, the direct environmental impacts of
well stimulation practice appear to be relatively limited. If these well stimulation technologies
enable a significant increase in production in the future, the primary impacts on California's
environment will likely be caused by the increase in production activities in general. Impacts of
increased production will vary depending on whether this production occurs in existing production
areas (both rural and urban), or in regions that have not previously been developed for oil and gas
production - as well as on the nature of the ecosystems, geology, and groundwater in the vicinity.
The scientific review carefully assessed the direct environmental, climate, and public health
impacts of well stimulation within the limits of available data. Records filed with state agencies
before the enactment of Senate Bill 4 do not comprehensively record well stimulation events.
Voluntarily submitted data, such as those available on FracFocus, although very useful, are not
required to be either complete or accurate. The limitations of the data are described throughout the
report in order to transparently qualify the conclusions.
Over the next year, CCST will lead an expert team, including Lawrence Berkeley National Laboratory
and the Pacific Institute, to produce the scientific assessment of well stimulation technology
required by Senate Bill 4, which mandates stronger state oversight of well stimulation within
California. This report will incorporate and expand the analysis done for BLM and will include more
recent disclosure data and a review of offshore and gas well stimulation not covered in the BLM
Information about the BLM oil and gas program is available on the BLM website.