LABORATORY STUDIES OF THE INFLUENCE OF RHEOLOGICAL CHARACTERISTICS OF CROSS-LINKED POLYMER SYSTEMS ON OIL PERMEABILITY AND DISPLACEMENT COEFFICIENTS
Oil recovery enhancement methods, mostly chemical ones, are widely applied in the course of development of oilfield hard-to-recover hydrocarbon reserves. Each reservoir stimulation technology features certain application conditions depending on the reservoir's initial geological and physical parameters and the current state of its development. A methodological approach to determination of rock oil permeability and displacement coefficients when testing compositions of technologies of physical and chemical methods of oil recovery enhancement based on laboratory studies of rheological properties of various grades of acrylamide polymer is presented. The methods have been developed in accordance with the requirements for core study. The list of equipment and basic characteristics of the filtration system, as well as the procedure for preparing working fluids and reservoir models for laboratory studies are presented. Laboratory research of rheological properties of gel systems was conducted subject to specifics of the technological process of preparation of components of viscoelastic composition at wellhead and its subsequent injection into formation. For this purpose, to determine the rheological characteristics of gel systems a specialised rheometer was used that allowed to record in a dynamic mode the data on changes in viscosity properties of the tested polymer systems prepared on the models of fresh, produced and Cenomanian waters in the well-formation pressure-temperature conditions. Based on the findings of laboratory studies it was shown that the trial injection of cross-linked compositions based on polyacrylamide (PAA) of FP-107 and Poly-T-101 grades that are able to increase manifold the final viscosity of polymer composition (2-3 times, and more) with temperature rise in low-salinity waters (produced and Cenomanian waters) enables greater process efficiency compared to acrylamide grade FP-307 that is currently used in the Company's fields.