Considering Shear Dilution and Threshold Pressure Gradient Heavy Oil Reservoir Nonlinear Numerical Simulation and Residual Oil Characterization

Abstract

Abstract A large number of experimental results show that, the flow of heavy oil in porous media does not conform to Darcy seepage law. Heavy oil has the characteristics of threshold pressure gradient and its viscosity decreases nonlinearly with the increase of velocity. Heavy oil is a non-Newtonian fluid, but currently commercial reservoir numerical simulation simulators (ECLIPSE, CMG) do not have nonlinear numerical simulation function for heavy oil. In this paper, a new Hg Equation is introduced to match the nonlinear relationship between heavy oil viscosity and velocity, and a new heavy oil nonlinear reservoir numerical simulator is developed considering the threshold pressure gradient and shear thinning characteristics of heavy oil. Based on the basic data of the SZ Oilfield, this paper established a well group conceptual numerical model, and used the newly nonlinear numerical simulator for heavy oil to study the effects of the threshold pressure gradient and shear thinning of heavy oil on the laws of remaining oil distribution and development characteristics. The numerical simulation results show that the remaining oil distribution law of the model considering the nonlinear seepage characteristics of heavy oil is very different from the normal model, which is reflected in the lower sweep coefficient and the lower remaining oil saturation of the mainstream line. Based on the numerical simulation results, this paper proposed an effective pressure gradient to evaluate the sweep range of heavy oil in the reservoir and an effective well distance calculation method is proposed. In the development practice of SZ oilfield, this method has achieved very good application results. The novelty of this paper is that considering the characteristics of threshold pressure gradient and shear thinning of heavy oil, a new nonlinear reservoir numerical simulator for heavy oil is developed. The Hg equation is proposed to match the nonlinear change of heavy oil viscosity with shear rate. Based on the numerical simulation results a new calculation method of effective well distance is proposed.