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AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Aliso Canyon Gas Storage Leak Disaster and Response


The Aliso Canyon natural gas storage field came into public view on October 23, 2015 as a result of a leak detected in one of its 115 storage/injection wells. The leak was the second largest gas storage leak in U.S. history, reported by S. Conley and co-authors in Science, March 18, 2016 to release 97,100 metric tons of methane. 10% of the release has been reported as ethane. The was largest such event in the U.S., in terms of greenhouse gas impacts, because explosion and fire converted the earlier methane to CO2. The field is the largest of the four fields serving southern California, with 86.2 billion cubic feet of working gas capacity. In addition to its size, the fifth largest in working gas nationwide, its ability to deliver massive quantities in a short time is a valuable operational feature. It can send out a maximum of 1.86 billion cubic feet per day, making it the fastest in California, the tenth fastest in the nation and, among depleted reservoirs, the fourth fastest in the nation (only salt domes are faster). Its capabilities are particularly useful for serving the electric power industry whose demands fluctuate sharply and which comprise 80% of SoCal Gas company's load (demand) in the summer. A relief well extinguished the leak on February 18, 2016. As of mid-June 2016, the field was still being withheld from operation while a series of integrity tests were being conducted on its 114 injection wells. Imposed by the state's Division of Oil, Gas and Geothermal Resources and further reinforced by legislation in May, these involve temperature and noise tests, followed by logging to inspect casing (thinning) and cement bonds with production casing and with the formation, running a multi-arm caliper tool to reveal deformation or thinning, and finally pressure testing. In May, SoCal Gas estimated total costs to reach $650 million, 15% each for well control and legal fees, and 70% for relocation expenses. Many entities have coordinated analysis of risk and development of procedures to avoid blackouts due to insufficient gas supplies, the first concern being able to serve high electricity demands during summer heat waves. This requires understanding planned and unplanned deliverability risks (pipelines) and electric system risks, separately and together. The event illustrates the close interdependence and urgent coordination required between gas transmission and storage, the electric sector, and a host of regulatory bodies.