Well Stimulation Treatment

Well Stimulation Treatment (WST) refers to processes performed on oil and gas wells to increase production. The various types of WST enhance the permeability of the geologic formation containing oil and gas.

The Division of Oil, Gas, and Geothermal Resources (DOGGR) oversees well stimulation treatments in California. DOGGR’s WST regulations increase operational transparency; reporting requirements, including disclosure of WST fluid chemicals; and neighbor notification with the opportunity for neighbors to seek baseline water quality testing. They require an extensive engineering review and well integrity evaluation for groundwater protection and seismic monitoring. This includes a stoppage for evaluation should any earthquake greater than magnitude 2.7 near a stimulation operation occur. The State Water Resources Control Board also must review all proposed projects to determine whether groundwater monitoring is required.

DOGGR is also responsible for verifying that well operators comply with regulations.

Inland District Well Stimulation Treatment Operation
Well Stimulation Treatment

Additional Information

WST Permit Index

WST Disclosure Data

Well Stimulation Map Data (Calstim'D)

Neighbor Notification and Water Sampling


Hydraulic fracturing (also known as fracking, hydrofracturing, or fracing) is a type of WST. Oil and gas operators sometimes use hydraulic fracturing when pore space in the rock making up the oil or natural gas reservoir is too tight to allow the flow of fluids or gasses to the well.

The hydraulic fracturing process involves a mix of fluids and substances called “proppants” injected at high pressure into an oil or gas reservoir. The mix and the force with which it is injected causes reservoir rock to fracture. When the fluids are removed, the proppants keep the cracks open. Natural gas or oil flow into the cracks and into the well.

Acid fracturing and acid matrix are other types of well stimulation.


For Operators

WST Reports

WST Final Environmental Impact Report (FEIR)

California Council on Science and Technology study "Advanced Well Stimulation Technologies in California"