Natural gas storage uses a confined geologic formation used to temporarily store and provide efficient and dependable supplies of natural gas to consumers, businesses and utilities. There are over 400 natural gas underground storage facilities in operation in the United States today with the capacity to store 3,900 Bcf. Approximately 86% of these facilities utilize depleted reservoirs. The remaining 14% utilize either salt caverns or aquifers.

Underground Storage Facilities in the United States
Source: Energy Information Administration, EIA GasTran Geographic Information System
Underground Storage Data Base

Depleted reservoir storage utilizes a depleted underground natural gas reservoir that originally contained oil and/or gas. Gas is injected back into the depleted reservoir in order to re-fill the reservoir. The withdrawal process for the gas in storage normally replicates the process originally used to produce gas from the reservoir in the first place. The conversion of a depleted gas reservoir for storage use traditionally involves drilling many new wells that enables a more rapid withdrawal of gas than was originally used to deplete the reservoir.

Types of Underground Natural Gas Storage Facilities

Only 13.5 percent of the natural gas California uses comes from in-state production. The remainder is delivered by pipeline from several production areas in the western United States and Canada. Once the gas arrives in California, it is distributed by the state's three major gas utilities. Central Valley will be connected to PG&E's transmission system. The connection with PG&E will provide Central Valley customers with access to Alberta, Rockies, San Juan, and Permian gas supply through the many pipelines that tie into PG&E. Central Valley will also have access to potential supplies from new LNG facilities being developed on the West Coast.

Source: California Energy Commission

Central Valley Gas Storage will provide statewide benefits by expanding the existing natural gas supply infrastructure in California and, more specifically, by increasing the total amount of natural gas storage capacity in northern California where storage is in high demand.