Experimental Study on the Enhancing Oil Recovery Mechanisms and Displacement Law of CO2 High Speed Flooding in Low Permeability Reservoirs
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Abstract
In order to clarify the production mechanism and development effect of CO2 pressure flooding in heavy oil reservoir, this study analyzed the action mechanism of CO2 on heavy oil by using phase simulation technology. Based on the finite element discrete method, a coupling model of seepage field and stress field was established to analyze the influence of injection pressure on fracture propagation behavior. Based on the simulation results of fracture generation, a numerical model considering the formation of complex fractures after CO2 composite pressure flooding was established for the simulation of reservoir production after pressure flooding. A numerical simulation method of CO2 pressure flooding for heavy oil reservoirs based on reservoir dynamic parameters was developed. The propagation behavior of fractures during CO2 pressure flooding was studied, and the technological parameters of CO2 pressure flooding were optimized. The simulation results show that the main mechanisms of CO2 flooding include reducing oil viscosity, expanding oil, enhancing oil fluidity, creating fractures near injection Wells to improve CO2 injection capacity and increasing formation pressure. The CO2 pressure flooding results of heavy oil show that CO2 has a good energy increasing effect, and CO2 migration is seriously affected by the heterogeneity of the reservoir. The gas overburden leads to the accumulation of CO2 in the upper part of the reservoir, and the viscosity reduction effect of the upper part of the oil is more significant. Through the optimization of CO2 pressure flooding process parameters for heavy oil, it is suggested that the pressure flooding injection pressure should be controlled within 40~50 MPa. The results of this study have certain guiding significance for the design and field application of CO2 pressure flooding in heavy oil reservoirs.
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