Underground hydrogen storage in a depleted gas field for seasonal storage: A numerical case study of the Tekirdağ gas field

Abstract

The growing attention towards hydrogen (H2) within the energy sector recently has necessitated the development of extensive H2 storage systems. Depleted natural gas reservoirs, which have been utilized to secure natural gas storage over an extended period, are widely regarded as a viable option for the large-scale storage of H2. This research study presents the results of numerical simulations that were conducted to analyze the seasonal storage of H2 in the Tekirdağ gas field, a relatively shallow-depth, low-pressure, and low-temperature gas field located in the Thrace region of Türkiye. The working gas capacity was estimated to be approximately 920 million standard cubic meters (Sm3) under a maximum reservoir pressure of 32 bar and a minimum reservoir pressure of 10 bar. To determine the injection and withdrawal capacities of the reservoir, the H2 ratio of the withdrawn gas, and the impact of the wells’ skin factor value on these parameters, cyclic storage simulations were conducted in three distinct cases. The estimated annual injection capacities for the final storage cycles of the three cases are 372.2 million Sm3, 276.6 million Sm3, and 419.2 million Sm3, and the obtained H2 withdrawal capacities are 347.8 million Sm3, 254.8 million Sm3, and 393.7 million Sm3, respectively. The differences in the H2 ratio of recovered gas among the three cases are especially noticeable during the initial two storage cycles. Nevertheless, similar purity values were achieved for H2 in all three cases during the last storage cycle. Based on the findings derived from the simulations, it can be inferred that depleted natural gas reservoirs offer a viable option for H2 storage in terms of both storage capacity and H2 purity. Although a negative skin factor value and subsequent high-rate withdrawal initially lead to a decrease in H2 purity, this drawback gradually diminishes over time.