Simulation on H<sub><b>2</b></sub>S Migration and Elutriation during Cyclic Operationof Underground Sour Gas Storage

The construction and operation of sulfur-containing gas storage are often more difficult than a non-sulfur storage facility due to the need to prevent environmental contamination from H2S leaks, as well as the corrosive effects of H2S on production facilities. Rapid elutriation of H2S from the reservoir during the construction of the gas storage is an effective way to avoid these problems. However, the existing H2S elutriation method has low efficiency and high economic cost, which limits the development of reconstructed gas storage of sulfur-containing gas reservoirs. To improve the efficiency of H2S elutriation in sulfur-containing gas reservoirs and enhance the economic benefits, a numerical simulation model of multiphase flow components was established to study the migration law of H2S in the multi-cycle operation of gas storage. Based on the H2S migrate law, the displacement H2S elutriation method was developed, and the elutriation mechanism and elutriation efficiency of the two methods were compared and analyzed. In addition, the main controlling factors affecting the H2S elutriation efficiency were investigated, and the H2S elutriation scheme of H gas storage was optimized. The results indicate that H2S migrates between near-well and far-well regions under pressure differentials. The traditional H2S elutriation method relies on concentration gradient diffusion, whereas the displacement elutriation approach leverages pressure differentials with higher H2S elutriation efficiency. For the displacement elutriation method, higher reservoir permeability enhances the peak-shaving capacity of the gas storage but has a minor impact on H2S elutriation when the formation permeability is between 30 and 100 mD. The elutriation efficiency is significantly higher when wells are drilled in the high structural parts of the reservoir compared to the low structural parts. Longer displacement elutriation time within a cycle improves H2S elutriation efficiency but reduces the working gas volume of the storage. Therefore, the optimal displacement time for H gas storage is 60 days. An optimized H2S elutriation scheme enabled the working gas to meet the national first-class natural gas standard within 10 cycles. This study elucidates H2S migration patterns, H2S elutriation mechanisms, and key influence factors on H2S elutriation efficiency, offering valuable technical insights for sour gas storage operations.