The main producing formations of Central-Khoreiver Uplift (CKU) fields are carbonate Devonian deposits (Famenian stage) that are characterized by predominantly hydrophobic wettability. Reservoir temperatures are around 70 °C and high salinity formation water – up to 210 g/l, hardness of water (Ca+Mg) - up to 20 g/l. Oil viscosity at reservoir condition is of 7 mPa·s, bubble-point pressure – 8 MPa, gas-oil ratio – 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 presents the process of designing pilot test to evaluating the efficiency of surfactant-polymer flooding in field conditions using single well chemical tracer test. The effective surfactant-polymer composition was selected on the basis of a set of key parameters measured in screening and complex laboratory testing. Filtration 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. To evaluating the efficiency of the selected composition in the field conditions, pilot test was designed using single well chemical tracer test. The main task of the pilot test is to determine the change in the residual oil saturation or the oil displacement efficiency during successive pumping of water and surfactant-polymer composition. With the help of dynamic modelling the optimal values of the pilot test parameters were obtained, such as: maximum injectivity; the size of the studied formation zone; required volumes of water, surfactant, polymer and tracers; duration of operations. The resulting design became the basis for drawing up a pilot program, which includes all the main technological operations and possible risks.
References
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