The controlling factors and distribution prediction of H_2S formation in marine carbonate gas reservoir, China

摘要

Generally, there are some anhydrites in carbonate reservoir, as H_2S is also familiar in carbonate oil and gas reservoirs. Nowadays, natural gas with high H_2S concentration is usually considered as TSR origin, so there is close relationship between H_2S and anhydrite. On the contrary, some carbonate rocks with anhydrite do not contain H_2S. Recently, researches show that H_2S is only a necessary condition of H_2S formation. The reservoir porosity, sulfate ion content within formation water, reservoir temperature, oil/gas and water interface, hydrocarbon and some elements of reservoir rock have great controlling effects on the TSR occurrence. TSR deoxidizes hydrocarbon into the acidic gas such as H_2S and CO2, and the H_2S formation is controlled byTSR occurrence, so the relationship among reaction room, the contact chance of sulfate ion and hydrocarbon, the reservoir temperature has great influence on the TSR reaction. H_2S has relatively active chemical quality, so it is still controlled by thecontent of heavy metal ion. Good conditions of TSR reaction and H_2S preservation are the prerequisite of H_2S distribution prediction. This paper builds a predictive model based on the characteristic of natural gas reservoir with high H_2S-bearing. In the porosity reservoir with anhydrite, the formation water is rich in sulfate and poor in heavy metal ion. Oil and gas fill and accumulate in the gas reservoir with good preservation conditions, and they suffered high temperature later, which indicates the profitable area of natural gas with high H_2S-bearing.