Chapter 2 : Failure Modes, Likelihood, and Consequences
Kuldeep R. Prasad
The general purpose of underground gas storage (UGS) is to meet varying demand for natural gas (methane, CH4) over daily to seasonal time scales in the face of constant rate gas production and limited pipeline transport capacity. In California, UGS is used to meet peak winter direct-use demands (home and business heating), to meet peak summer demands for electricity (e.g., air conditioning), to balance intermittent renewables (wind and solar), and to carry out price arbitrage (see Chapter 2 for complete details on the role of UGS in the California energy system). UGS is carried out in California by connecting underground storage reservoirs to the network of transmission pipelines that deliver natural gas from its sources in gas reservoirs throughout the western U.S., including local California natural gas reservoirs, to its customers in California. The California UGS system in 2016 comprises 12 UGS facilities, four in Southern California, and eight in Central and Northern California with a capacity to deliver between just under 400 Bcf of natural gas. The total capacity of the 12 reservoirs is significantly higher than 400 Bcf because much of the gas in the UGS reservoirs remains in the reservoir as cushion gas, which is essentially gas whose decompression provides the driving for production of the last bit of working gas on any production cycle. These underground reservoirs are all more than one thousand feet deep and are accessed by deep wells. At the depth of the reservoirs, natural gas is under high pressure (e.g., >1000 psi (~7 MPa)). The handling and containment of high-pressure natural gas, which is highly flammable and explosive, entails risk. If a loss-of-containment (LOC) incident occurs, fire and/or explosion are possible with potentially catastrophic consequences for workers, the public, and the UGS infrastructure itself.
Natural Gas Storage in California
California Council on Science and Technology, Berkeley, CA