Analysis of oil rim transformation: Cases of Goryuchkinskoye and Yuzhno-Generalskoye oil fields in Saratov oblast

Background. Gas and oil, as well as gas condensate, deposits are challenging objects for research and development. Moreover, as a rule, oil rim reserves are difficult to extract. The advanced production of the gas cap leads to man-made transformations of oil reserves, which significantly complicates their extraction and poses extraordinary tasks for geological and field monitoring and justification of effective geological and technological measures at such facilities. A significant number of deposits, where such advanced development of the gas cap is practiced, are located within the West Siberian, Volga-Ural, and Timan-Pechora oil and gas provinces. The remaining recoverable reserves here exceed the amount of one billion tons. Aim. Analysis of the transformation process of oil rim reserves in the Bobrikovsky horizon deposits of two fields — Goryuchkinskoye and Yuzhno-Generalskoye — in the Saratov Oblast (Russia), along with identification of the main factors affecting the transformation of sub-gas reserves. Materials and methods. The results of geological and field research, development data, and existing geological and filtration models were used as source materials. Geological and commercial analysis was used as the main research method, taking into account the results of reservoir modeling. Results. The considered deposits of the Bobrikovsky formation of the Goryuchkinskoye and Yuzhno-Generalskoye fields have entered an intensive stage of transformation of oil rims. Already at the initial stage, their development was characterized by an active formation of water cones and subsequent movement of oil into the sections previously occupied by gas. The deposits entered the stage of intensive transformation following 5–7 years of the commencement of development. The high reservoir properties and activity of the aquifer contributed to a fairly efficient production of oil reserves. Even without the use of reservoir pressure maintenance methods, significant degassing of oil did not occur. Conclusion. An improved understanding the described processes makes it possible to substantiate effective approaches to regulating the development of deposits, as well as to extracting oil from transformed deposits. This is particularly relevant for objects operated under unfavorable geological conditions and when the transformation process entails irreversible negative changes.