Nonlinear flow numerical simulation of low-permeability reservoir

Abstract

A nonlinear flow reservoir mathematical model was established based on the flow characteristic of low-permeability reservoir. The well-grid equations were deduced and the dimensionless permeability coefficient was introduced to describe the permeability variation of nonlinear flow. The nonlinear flow numerical simulation program was compiled based on black-oil model. A quarter of five-spot well unit was simulated to study the effect of nonlinear flow on the exploitation of low-permeability reservoir. The comprehensive comparison and analysis of the simulation results of Darcy flow, quasi-linear flow and nonlinear flow were provided. The dimensionless permeability coefficient distribution was gained to describe the nonlinear flow degree. The result shows that compared with the results of Darcy flow, when considering nonlinear flow, the oil production is low, and production decline is rapid. The fluid flow in reservoir consumes more driving energy, which reduces the water flooding efficiency. Darcy flow model overstates the reservoir flow capability, and quasi-linear flow model overstates the reservoir flow resistance. The flow ability of the formation near the well and artificial fracture is strong while the flow ability of the formation far away from the main streamline is weak. The nonlinear flow area is much larger than that of quasi-linear flow during the fluid flow in low-permeability reservoir. The water propelling speed of nonlinear flow is greatly slower than that of Darcy flow in the vertical direction of artificial fracture, and the nonlinear flow should be taken into account in the well pattern arrangement of low-permeability reservoir.