Feasibility study of a natural gas storage prospect reservoir using decline curve and hysteresis analysis

Underground natural gas baseload storage facilities are a vital part of the world's natural gas infrastructure. These facilities allow Exploration & Production (E&P) and transmission pipeline companies to utilize natural gas assets year round while providing means for consistent gas supply throughout the year. The purpose of this thesis is to present a process in which a feasibility study can be conducted for a prospective baseload storage facility. This was accomplished by explaining 1) the theory of natural gas storage reservoir engineering; 2) geologic consideration for underground storage prospects; 3) design of a new underground baseload facility using decline curve analysis and hysteresis analysis; and 4) a detailed economic analysis of a storage prospect. A depleted natural gas reservoir was evaluated for its potential to become an underground baseload storage facility for natural gas. For this underground reservoir, it is estimated the Original Gas in Place (OGIP) was 59.4 Billion Cubic Feet (BCF) using hysteresis analysis. The cushion gas requirement was solved to be 50% of the OGIP, or 29.7 BCF. There is currently 7.4 BCF of native gas present in the reservoir. The required injection cushion gas requirement is estimated at 22.3 BCF. The maximum field deliverability was estimated to be 284.3 Thousand Cubic Feet per Day (MCF/D) at a reservoir pressure of 868.5 psia. The minimum field deliverability was estimated to be 83.8 MCF/D at a cushion gas pressure of 434.1 psia. Maximum and minimum deliverabilities assume 30 injection/withdrawal wells are present at 6 different well pads throughout the field. After analyzing three different economic scenarios for the prospective storage field it was determined this project is not economically feasible under current market conditions. Recommendations for future work include the operating company conducting a 3D seismic survey and re-evaluating the project using 3D reservoir simulation evaluating the possibilities of 1) using horizontal drilling to minimize number of wells, 2) simulate storage well performance if vertical wells are hydraulically fractured, and/or 3) simulate if the prospective storage facility can be pressurized over the original discovery pressure.