Well Stimulation

Technological developments in oil and gas exploration and production, including well stimulation, have greatly increased the energy security of the United States by ensuring a long-term, ample, affordable and reliable supply of domestic energy and helped to reduce our nation’s dependence on foreign imports. Hydraulic fracturing and acid matrix stimulation are engineered practices defined under California law that improve the productivity of targeted oil and natural gas formations in certain fields, thereby reducing the number of wells and the surface footprint needed to produce the same quantity of oil and natural gas. In 2017, California Resources Corporation (CRC) used hydraulic fracturing on less than 7 percent of the wells we drilled, and did not use acid matrix stimulation.

Hydraulic Fracturing

Hydraulic fracturing uses water pressure to increase the contact area of the wellbore via small fractures in hard or tight rock formations so that the oil and gas can move more freely to the production well. A hydraulic fracturing operation usually takes a few hours and occurs once in the targeted oil and gas formation during the decades-long life of the production well. Hydraulic fracturing fluids are often more than 99 percent water and an inert material such as sand. Service companies select additional ingredients based on the mineralogy and geology of the oil and gas formation for specific tasks like carrying the sand or inhibiting corrosion. These ingredients are commonly found in a variety of household products and in widespread commercial and industrial applications. Their properties are well understood.

Because of California’s geology, hydraulic fracturing is not used in most oil and gas wells in the state. Only about 20 percent of the state’s production comes from wells that have undergone hydraulic fracturing. This is much different from the rest of the country, where the U.S. Energy Information Administration (EIA) estimates that two-thirds of U.S. natural gas production and over half of U.S. crude oil production in 2015 came from wells that were hydraulically fractured. By comparison to CRC’s targeted use of well stimulation, operators in many oil and gas fields in Colorado, New Mexico, North Dakota, Pennsylvania and Texas use hydraulic fracturing on nearly every well. The California Council on Science and Technology has also noted that California operators typically require far less water than is customarily applied in other states. As a result, use of water for well stimulation in California has no effect on water availability for other users.

Acid Matrix Stimulation

Acid matrix stimulation is a separate well stimulation technique that can increase the permeability of certain oil and gas formations by dissolving minerals deposited in the rock with a low concentration solution of acid in water. Its properties are well understood. This process requires far less water and energy than hydraulic fracturing and the acid is rapidly neutralized by the minerals in the oil and gas formation near the wellbore.

Regulation and Oversight

The State of California has been effectively monitoring well stimulation for decades as part of its comprehensive rules that address all aspects of oil and gas development. In 2013, California’s legislature enacted Senate Bill 4 (SB-4), the most stringent law governing well stimulation of any oil and gas producing state or country. SB-4 created a new well stimulation permit program and required the state to prepare an environmental impact report regarding well stimulation. The state’s Division of Oil, Gas, and Geothermal Resources (DOGGR) of the Department of Conservation reviews permit applications submitted by CRC and other operators that provide detailed information about the well, the stimulation job, and the presence or quality of local ground water. Operators are also required to make detailed disclosures to multiple agencies and nearby property owners, prepare water management and groundwater monitoring plans and conduct ground water and air monitoring of certain well stimulation jobs under the supervision of state agencies including the State Water Board and the California Air Resources Board.

Public Disclosure

CRC is committed to public disclosure about our hydraulic fracturing and well stimulation practices. In 2011, CRC’s predecessor was an early participant in FracFocus®, a website created by the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission to provide for well-specific voluntary disclosure of hydraulic fracturing operations, including the ingredients used in hydraulic fracturing fluids. In addition to providing a national registry, the website provides factual information about hydraulic fracturing and groundwater protection.

DOGGR’s website also provides details about CRC’s well stimulation jobs, permits and other documents required under SB-4 and the statewide environmental impact report on well stimulation.

During 2016, the state developed its well stimulation permitting process under the final SB-4 regulations that took effect in July 2015, so CRC performed no well stimulation jobs that year. In 2017, CRC conducted 15 well stimulation jobs, all using hydraulic fracturing, on less than 7 percent of the wells we drilled during the year.

CRC prepares water management plans for all well stimulation jobs and submits data about water sources and quantities used to DOGGR. CRC used a total of 7.35 acre-feet of non-potable water for well stimulation, an average of less than 160,000 gallons per job or less than one quarter of an Olympic-size swimming pool. Importantly, CRC used no potable water for well stimulation in 2017. The water sources and volumes for CRC’s stimulation jobs are shown in the following table:


Water Source Water Volume in Acre-Feet Percent of Water Volume
Recycled Produced Water 0.73 10%
Potable Water 0.00 0%
Non-Potable Fresh Water 6.62 90%
Total Water Used in Well Stimulation 7.35  

CRC’s very limited water use for well stimulation does not in any way impair access of others to water. These jobs occurred within longstanding oil and gas fields in the Elk Hills area. In addition, the non-potable fresh water used in all of CRC’s 2017 well stimulation jobs could only support about two acres of row crops.

After conducting well stimulation, the produced fluid is captured processed within a closed system. The produced water is typically reinjected into oil bearing formations in the field for improved oil recovery.

Groundwater Monitoring

CRC actively implements detailed groundwater monitoring plans approved by the State Water Board for well stimulation in areas with protected groundwater. Those plans include both pre-stimulation sampling for baseline groundwater quality and periodic post-stimulation sampling and analysis for more than 100 compounds. CRC obtained the state’s first approved well stimulation permit under the final SB-4 regulations in late 2016, as well as the state’s first approved SB-4 groundwater monitoring plan. CRC’s groundwater monitoring plans and sample results can be reviewed on the State Water Board’s GeoTracker website. CRC has not experienced any spills or incidents during our well stimulation activities under SB-4, and groundwater monitoring has found no impact from well stimulation activities.

For more information, view our Hydraulic Fracturing infographic (PDF) or refer to the FracFocus, GeoTracker or DOGGR websites.