Comprehensive modeling and developing a software for salt cavern underground gas storage

Abstract

• Comprehensive modeling of different elements of the underground gas storage in salt caverns was carried out. • Main parts of modeling are salt leaching process, gas injection and production process, modeling formation of hydrates and modeling of thermal behavior of the cavern. • This study presents the first integrated modeling in of the gas storage process in salt domes. • Comparison of the results of the proposed model with available data and other software in this field shows that the built software in this project can be confidently used for salt cavern gas storage purposes. Underground natural gas storage (UGS) is significant from strategic and technical points of view. Gas consumption in the cold seasons increases dramatically and makes gas supply a serious challenge. Underground natural gas storage as an effective and permanent strategy can meet the needs of different parts of the country at the peak of consumption. UGS is possible in different methods including storage of gas in depleted hydrocarbon reservoirs, aquifers, abandoned mines, and salt caverns. Because of technical and economic considerations including very low permeability and porosity of salt layers, a high delivery capacity, low surface requirements, and the presence of salt domes in different regions of the country, salt caverns are regarded as a suitable option for storage of natural gas. Due to the high cost of data acquisition in storage/production operations and difficulties of decision-making based on crude data, modeling of these processes can provide a thorough understanding before the operation. Also, a model can effectively contribute to the analysis of the available data from storage and production processes. To the best of our knowledge, this is the first modeling study conducted by integrating all main elements of the gas storage process in salt caverns. This modeling includes salt leaching, injection, and production of the gas, heat transfer effects, and hydrate formation. The most important elements of the process were modeled mathematically and the resulting equations were solved numerically using the most common programming languages including FORTRAN, Visual Basic, and MATLAB. The integrated model was then converted into a user-friendly software “UT-SCUGS”, which is believed to be the first software with the prescribed capabilities. The prediction made by UT-SCUGS was compared with the published data and the available storage/production software (SGSC and SALGAS), and a good agreement was observed in most respects.