Due to high reactivity and toxicity, hydrogen sulfide is an undesirable component of oil associated gas, it reduces economic value of associated gas and shortens the service life of technological equipment. In this paper we consider the main results of integrated geological, geochemical and hydrodynamical studies for determination of the causes of the origin and mechanisms of hydrogen sulfide formation in the composition of oil associated of the oil field on the territory of the Orenburg region. The research is focused on creating a quantitative model for predicting the generation of hydrogen sulfide depending on the technological parameters of the field development. The first stage of our research was determination of the hydrogen sulfide genesis n the oil associated gases and formation water by the isotopic analysis of sulfur. The component composition of formation water and gases was also studied. The isotopic composition of hydrogen sulfide in the oil associated gas corresponds to the range of bacterial sulfate reduction (BSR). The isotopic composition of water-dissolved sulfides is also typical of BSR processes. According to the reservoir temperatures, sulfur isotopic composition, the presence of reservoir waters with water-dissolved sulfates and organic components, hydrogen sulfide in the oil associated gas can be classified as biogenic, formed as a result of bacterial reduction of sulfates in reservoir waters. This process can take place directly in the reservoir area in the formation waters of the field. This process can take place in the formation waters directly in the reservoir area. The next stage of research is the isolation and study of the mechanism of the vital activity of sulfate-reducing bacteria to determine the boundary conditions for the existence of bacteria, the dependence of the change in the reduced hydrogen sulfide on the parameters of the field development for numerical modeling and predicting the dynamics of hydrogen sulfide formation.
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