CHAPTER 7 – Optimization of Underground Storage Facilities

This chapter discusses the optimization of underground storage facilities. The amount of flexibility to achieve optimum economic conditions in underground storage facilities varies with each case. There are times when the requirements of the storage needs and the limitations of the reservoir chosen are so confining that there is little room for economic maneuvering. Some of the factors that affect storage facility characteristics and affect the economics are listed in the chapter. The variable factors are the number of wells, the flowing wellhead pressure, and the working-gas to cushion-gas ratio. Other factors are variable to some degree. These include the size of the gathering system piping, and the size of the transmission line connecting the storage facility to the rest of the transmission system. The exception of cushion gas, the largest single cost item in a storage facility is the compressor installation. This provides the pressure rise necessary to counteract the various pressure drops in the system. One of the cases to be considered is the effect that the working gas volume has on the wellhead flowing pressure limitations. It is found that the total annual cost of service is divided by the total working gas to determine the cost of service per Mcf of working gas.