Document Type : Research Paper
State Key Laboratory of Offshore Oil Exploitation, Beijing, ChinaCNOOC Research Institute Co., Ltd., Beijing, China
Institute of Petroleum Engineering, China University of Petroleum, Beijing China
The preformed particle gel (PPG) oil flooding system has several problems: (1) in the process of injection, particles easily settled and block the end face, which the process results in high pressure, and (2) the matching relationship between PPG particle size and formation pore throat has not been quantified sophisticatedly. To have a better description of the matching relationship between the median particle size of the dispersed phase and the pore throat diameter of the formation, its relationship has been quantified by us through the combination of core physical simulation and thin-tube experiments. Moreover, a calculation method of equivalent pore throat diameter has been proposed based on the principle of compact packing, which is more suitable for a sand-filled pipe model. To improve the performance of the system, the polymer and surfactant have been added into the PPG solution. The result indicates that when the pore throat diameter is between 1 to 5 times more than the median particle size of the dispersed phase, the dispersed phase can enter the pore throat smoothly, and the plugging rate is over 50%, which it means that the plugging is effective. When the pore throat diameter is more than 12 times of the median particle size of the dispersed phase, the plugging rate is less than 30%, and the effective residual resistance coefficient cannot be established. In order to improve the suspension performance of PPG particles, the polymer was added to the solution. In the presence of polymers, the suspension performance of PPG particles was greatly enhanced. Under the same injection volume, the PPG + polymer + surfactant system has the best oil displacement performance.