An Integration Method for Assessing the Operational Reliability of Underground Gas Storage in a Depleted Reservoir

Abstract

Underground gas storage (UGS), a key component of a natural gas pipeline network, can not only be used as an emergency gas source under a pipeline system failure situation but it is also available for seasonal peak shaving under pipeline system normal operation. Therefore, in order to meet the natural gas needs, it is of vital importance to safeguard the security of UGS operation and assess the reliability of UGS. The aim of the overall study is to develop an integration method for assessing operational reliability of UGS in a depleted reservoir under different injection-production scenarios, whereas existing studies only assess a single component or subsystem reliability. According to function zoning, UGS is separated into reservoir, well system, and surface system, and reservoir and surface system are connected through well system. The well system contains multiple injection/production wells. For the first step of the reliability assessment, the hydraulic calculation, including the gas injection process calculation and the gas production process calculation, is adopted to obtain the operational parameters of each component in UGS. Next, the reliability of the reservoir, injection/production well, and equipment in surface system is evaluated using operational parameters and a Monte Carlo approach. The reliability of the subsystem, such as the well system and surface system, is then calculated according to system reliability theory. Finally, operational reliability of UGS is obtained, which reflects the capacity of performing gas injection-production function. Two test cases are given to illustrate the integration method.