The San Joaquin Valley is a small geosynclinal basin between the Sierra Nevada and Coast Ranges of California. The structural axis of the basin lies close to the western margin of the valley. Gas is found in a variety of structural and stratigraphic traps. Typical fields representing gas production from traps of different types and rocks of different ages are described.

The San Joaquin Valley natural gas reserves of approximately 4.7 trillion cu ft constitute about 46 per cent of the total gas reserves in California. Ninety per cent of the gas reserves of the San Joaquin Valley are in the form of wet or casinghead gas associated with oil reservoirs as a free natural gas cap or in solution with the petroleum. Some gas is recycled for pressure maintenance and storage. Gas is produced from rock units ranging in age from Late Cretaceous to Pleistocene. The wet gas comes mainly from Miocene rocks and the dry gas from Pliocene rocks.

California's gas industry began in 1910 when the first pipelines were laid from Buena Vista Hills to Bakersfield. Expansion has continued through a period of oversupply in the late 1920's to the present period of insufficient supply from local sources.

The search for and production of additional natural gas reserves continues in the San Joaquin Valley, but intensive efforts and important recent contributions to gas reserves of California also have been made in northern California and offshore.