Case Study: Natural Gas Storage in Federal Waters Offshore California

Abstract

Abstract The U.S. Pacific Outer Continental Shelf (OCS) Region offshore California has over fifty years of production and development history. As of 2018, more than 1.35 billion barrels of oil and 1.85 trillion cubic feet of natural gas has been produced from three sedimentary basins in the Pacific OCS1. As part of the Bureau of Ocean Energy Management's (BOEM) mandate to sustainably manage development of U.S. OCS energy and mineral resources in an environmentally and economically responsible way, it is paramount that conservation and mixed-use projects such as underground gas storage be evaluated, adjudicated, and monitored to maximize utility of existing OCS offshore infrastructure. Through 2018, only a few underground gas storage projects have been undertaken in the entire U.S. Outer Continental Shelf (OCS) federal waters. The Sockeye Field Underground Gas Storage project in the Santa Barbara channel is a unique example of alternative reservoir use, as it is the only such project initiated and successfully executed in the Pacific OCS Region. Gas injection commenced short-term in 2002 and was effectively formalized in 2005 through an agreement between the Sockeye Field Operator and BOEM's predecessor agency, the Minerals Management Service (MMS). From the inception of the project through 2017, total gas volume injected and withdrawn was 2.3 Bcf and 582 Mcf respectively. This paper presents the results of the reservoir modeling study prepared for the Sockeye Field gas storage project. In this integrated study, BOEM utilized available 3D post stack time-migrated seismic reflection data, digital well log data, production data, and other geologic information to develop a comprehensive structural and petrophysical model of the Sespe sandstone reservoir. This study scrutinized segmentation of the Sespe hydrocarbon reservoir and, the suitability of the Sespe reservoir for storage of produced natural gas from the Sockeye Field. Frhe results of the reservoir modeling, operator's cumulative gas production and injection indicate this gas storage scenario provided an energy source for offshore facility operations, precluded the need for external gas buy-back, and lengthened the productive life of the Sockeye Field. In addition, this project also demonstrated that nearby analog reservoirs in the Pacific OCS may be suitable for future underground gas storage.