Hydraulic fracturing, commonly known as fracking, injects high pressure volumes of water, sand and chemicals into existing wells to unlock natural gas and oil. The technique essentially fractures the rock to get to the otherwise unreachable deposits.

The Monterey Shale, a geologic formation running the length of the San Joaquin Valley, has been a particular focus and is believed to be home to large amounts of untapped crude. There also has been exploratory fracking elsewhere in California, including well sites along the edges of the Sacramento-San Joaquin Delta—though the more permeable soil there makes it less attractive to operators. Informal evidence also suggests that the majority of California’s wells may already be fracked, particularly in Los Angeles, Santa Barbara, Kern, Ventura and Monterey counties.

California is the fourth largest producer of crude oil in the United States and has a long history of oil exploration.

California’s fracking industry differs from other states. Elsewhere, fracking done for natural gas production involves large operations. The fracking in California is primarily for crude oil rather than natural gas and occurs on a smaller scale.

While hydraulic fracturing has taken place in California for more than 50 years, the use of fracking has grown and the technique has generated controversy due to concerns that fracking could trigger earthquakes or contaminate adjacent groundwater aquifers. 

In 2024, California’s Geologic Energy Management Division (CalGEM), which oversees oil drilling operations in the state, adopted regulations that phased out hydraulic fracturing in California. 

Updated May 2026