The main producing formations of Central-Khoreiver Uplift fields are carbonate Devonian deposits (Famenian stage) that are characterized by predominantly hydrophobic wettability. Reservoir temperatures is around 70 °C and high salinity formation water is up to 210 g/l, hardness of water (Ca+Mg) is up to 20 g/l. Oil viscosity at reservoir condition is 7 mPa·s, bubble-point pressure is 8 MPa, gas-oil ratio is 36 m3/t. The current reservoir pressure is about 20 MPa. A study is currently in progress these object to evaluate the injection of different chemical agents to increase oil recovery factor. The paper discusses the process of development of surfactant-polymer flooding technology for carbonate reservoirs with high salinity formation water and high reservoir temperature. The initial selection of compositions for enhanced oil recovery included experiments to assess the physicochemical properties: viscosity, interfacial tension with oil, etc. These parameters are determined under conditions close to reservoir conditions. The effective surfactant-polymer composition was selected on the basis of a set of key parameters measured in screening and complex laboratory testing. Coreflooding experiments on composite core model were conducted to evaluate the efficiency of selected composition. At the target concentration values, an additional oil displacement coefficient of 7% is provided after pumping one pore volume of the surfactant and 14% after pumping one pore volume for the surfactant-polymer composition. The effectiveness of surfactant and surfactant-polymer compositions was confirmed in-situ with single well chemical tracer test (SWCTT) conducted at the oilfields of RUSVIETPETRO JV.
References
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