Advanced Well Stimulation Technologies in California
COMPLETED: July 2016
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 agriculture.
- 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 report.
Information about the BLM oil and gas program is available on the BLM website.