L41015 Feasibility of Inert-Gas Cushions in Gas Storages

Abstract

The use of permeable underground formations to store natural gas for subsequent withdrawal has assumed major importance in recent years. One of the requirements for such operations is an initial quantity (cushion) of compressed gas in the storage to furnish the expulsive energy for the removal of the gas (working gas) desired to be withdrawn. Usually the cushion gas is natural gas already present in the selected reservoir or is that amount of injected gas left in the storage at the end of the withdrawal period prior to the following injection period. In many storage operations the cushion gas represents a large investment; consequently, the use of a relatively inexpensive inert gas is desirable. As mixing of the inert gas cushion with the stored natural gas is undesirable, the various mechanisms tending to bring about such mixing were the subjects of both theoretical and experimental studies.