Experimental and numerical study of enhanced heavy oil recovery by chemical flooding

Chemical flooding has great potential for improving heavy recovery, especially for those heavy oil reservoirs not applicable for thermal recovery techniques. Experimental and numerical studies were conducted to improve understanding of the mechanisms involved in heavy oil recovery processes.;The relationship between heavy oil recovery improvement and the effective viscosity of polymer solution was experimentally investigated. An appreciable oil recovery increment is obtained by polymer flooding when the polymer viscosity is above a certain value. There exists an optimum value of polymer viscosity, above which the increase in polymer viscosity is less effective in improving oil recovery. Both the minimum and the optimum values of the polymer viscosity increase with increasing heavy oil viscosity.;Heavy oil recovery was effectively improved in alkaline and alkaline/surfactant flooding tests. The pressure response and oil recovery improvement were numerically simulated, including the chemical adsorption, interfacial tension reduction and in situ generation and flow of W/O or O/W emulsions. The extremely high viscosity of W/O emulsion increases the resistance to water phase flowing in water channels, which is simulated by a decrease in relative permeability to water. The formation of O/W emulsion lowers the mobility of water when oil droplets are trapped at small pore throats, which is represented by the decrease in local permeability. Field scale simulations show promising results of chemical flooding for heavy oils.;A parallel-and-serial-type interacting tube bundle model was developed using capillaries with equilateral triangle cross sections. The model is applied to simulate the trapping phenomenon in immiscible displacements and heavy oil recovery processes. Simulation results are in qualitative agreement with those obtained from laboratory experiments in the actual porous media. This pore scale model has a great potential to be a useful tool to relate the macroscopic flow properties to the microscopic controlling mechanisms.;Experimental studies on heavy oil-water two-phase relative permeability curves show that relative permeabilities are functions of oil viscosity. Both the oil and water relative permeability curves shift to lower values with the increase in oil viscosity. The residual oil saturation increases linearly with the logarithm value of oil viscosity.