To meet with the energy strategy, some natural gas reservoirs in Ordos Basin are planned to use as gas storages. However, most of the gas reservoirs have high content of H2S. If they were operated without parameters optimization, it would put reservoir engineers as well as the environment at rick. Thus, optimization of injection and production parameters of these sour gas storages is urgently needed.
In the paper, using numerical method, the movement mechanism of H2S is studied. With the sensitivity analysis, the effects of some critical factors on H2S mole fraction in produced gas are investigated including ultimate recovery factor, injection rate, production rate, and injection-production rate ratio. Based on the results of the sensitivity analysis, optimal injection-production parameters are selected for a gas storage S24 in Ordos Basin.
The results show that the H2S mole fraction in produced gas decreases as the injection-production cycle number increases. When the cycle number reaches 5, the H2S mole fraction is relatively stable. Additionally, the H2S mole fraction in produced gas hinges heavily on ultimate recovery factor, injection rate, production rate, and the injection-production rate ratio. The decrease amplitude of H2S mole fraction increases as ultimate recovery factor, injection rate, and injection-production rate ratio increase; it decreases as the production rate increases. Numerical results show that after 4 cycles of the operation with the optimal parameters, the produced natural gas from S24 gas storage can reach the quality standard II of commercial natural gas, which is safe for humans and environment.
This study provides us with key technical references for operation of the sour gas storages to ease the contradiction between energy supply and demand.