Development and Testing of a Comprehensive Gas Storage Reservoir Performance Model
Authors: Vikas Shree , Gabriel Steven , Mohan Hitesh , Becker Alan 
Published: December 2007

Abstract
As gas storage facilities become more a marketing tool and less a pipeline operational tool the criteria for using storage will change. A comprehensive Storage Reservoir Performance Model (SRPM) has been developed which can be used as an effective screening tool to characterize the performance potential of gas storage prospects. The purpose of SRPM is to provide an analytical tool for the evaluation of storage reservoir performance under alternative economic, technology and market conditions. The model is capable of evaluating existing gas storage performance for a specific production and injection schedule, which is derived from the working gas volume and peak rate requirements. The model can also evaluate the potential of new storage projects at a level of detail, sufficient to permit an integrated, geology/engineering/economic assessment for a variety of technology and operational scenarios.
A basic engineering type curve approach, modified from evaluation methods used in classical well test analysis, predicts both gas injectivity and deliverability in storage reservoirs. The model consists of various modules that are linked together to perform reservoir-level prediction performance calculations for depleted gas reservoirs, aquifers and salt dome caverns. Operating cost algorithms have been developed to predict compression, injection, production and processing costs over time. An economics module permits the evaluation of gas storage capital costs and injection/production costs (rather than development and production costs alone), as well as an income stream based on service charges related to storage (rather than gas sales revenue alone). Various screening criteria were devised and used in bracketing the range of reservoir and non-reservoir properties deemed reasonable for storage project implementation or expansion. A database of reservoir rock and fluid properties was developed for approximately 400 existing and 140 proposed storage sites that were screened using these criteria. The model can be applied to these reservoirs to assess their potential performance under various technology and economic scenarios. Hence, the model is capable of addressing various research and development needs to enhance the performance of gas storage projects to meet market demand. This storage model is an integral part of the Gas Systems Analysis Model (GSAM) developed under the sponsorship of the US Department of Energy.

Introduction
Recent changes within the natural gas industry, brought about by regulatory changes and market forces, have created a business environment that requires gas producers, marketing companies, and consumers to create and maintain gas supply and delivery systems to meet regional, local, and market-specific requirements. Historically gas storage was an integral part of pipeline operations used to maintain pipeline flow and to meet the specific demands of gas customers. As gas marketers, distributors, and customers assume more and more responsibility to secure gas supplies and transportation capacity, storage becomes increasingly important to them for maintaining supply as well as deliverability at a competitive price. The function of storage has hence changed from strictly an operational facility to a business center (frequently associated with market hubs) that can affect the supply/demand balance and ultimately the price of natural gas.
Gas storage facilities were, at first, located only at the demand-ends of the pipelines.