Prediction of pressure and temperature changes in the salt caverns of Tuz Golu underground natural gas storage site while withdrawing or injecting natural gas by numerical simulations

Abstract

Tuz Golu (Salt Lake) Underground Gas Storage (UGS) Project in Turkey is being implemented. In some of salt caverns, natural gas is currently stored. While analyzing the data of Tuz Golu UGS project, it was observed that this location is appropriate for safe underground natural gas storage due to its rock salt with high purity and very low permeability. In this study, many numerical simulations for a salt cavern in Tuz Golu UGS project at different gas withdrawal and injection rates were conducted by using TOUGH + RealGasBrine simulator. According to the results of these numerical simulations, the temperature inside salt cavern reduced below 0 °C from 53 °C within 20 days at a rate of gas withdrawal of 3.33 million standard m3/day due to Joule-Thomson effect. The temperature inside salt cavern reduced below 0 °C within 25 days, 40 days, and 60 days at a rate of gas withdrawal of 2.5, 1.67, and 0.833 million standard m3, respectively. In order to avoid fracture around the walls of salt cavern, the temperature change inside salt cavern should not be higher than 30 °C. In the numerical simulations, there is no gas seepages from the salt cavern to other neighbor salt caverns, which are 600 m away owing to very low permeability of salt rock in the study area. The implication of this study is that gas withdrawal and gas injection profiles are quite important to keep the temperature inside salt caverns at an optimum range for safe natural gas storage.