GRl-95-0466 Inert Base Gas Field Experiment

IGTs research efforts in the laboratory and over a decade of field experience of inert gas (nitrogen) application in French underground gas storage fields clearly indicate that replacement of base gas with less-expensive natural gas is feasible. The information from lab tests and a systematic procedure developed earlier were used to apply inert gas in the U.S. storage fields. This procedure for inert gas application was first applied in the Simpson Chapel field operated by the Citizens Gas and Coke Utility Company. This report summarizes the efforts of the second field test in the Shirley gas storage field, which belongs to Equitrans. In the Shirley gas storage field, a target area was selected and evaluated by completing four wells, conducting reservoir and tracer testing to determine its suitability for inert gas injection. Reservoir modeling was indicated that in the best option, with the help of existing wells in the target area, 300 MMCF or 5% of the total base gas can be replaced with nitrogen without jeopardizing the pipeline quality of working gas. In this process, a total of 400 MMCF of natural gas would be recovered from the target area. In addition to a one-time cost benefit (due to the price differential between natural gas and nitrogen), inert gas injection would also cut down an equivalent amount of natural gas migration and provide another opportunity to replace 200 MMCF of base gas with nitrogen in the next 20 years. FERC approval to conduct inert gas injection in the Shirley field has been obtained by Equitrans. Inert gas injection in the target area is expected to start in the summer of 1999, following the ongoing gas withdrawal from the target area to create a pressure sink.