动态渗透率三维油水两相低渗透油藏数值模拟

考虑流体在低渗透油藏流动过程中的非线性渗流特征和启动压力梯度的影响，基于动态渗透率的概念，建立了综合考虑非线性渗流和拟线性渗流的三维油水两相油藏数值模拟数学模型，通过全隐式差分格式建立了低渗透油藏数值模拟数值模型，并采用预处理共轭梯度法进行了求解。通过对均质油藏五点法井网和大庆油田某区块的计算结果表明，启动压力梯度对低渗透油藏的压力场有着显著的影响，在定产条件下，启动压力梯度越大则压力变化越剧烈，压降的影响范围越大，注采井间的压力梯度越高。由于非线性渗流规律较好地表达了流体在低压力梯度下的流动规律和最小启动压力梯度的影响，因此采用非线性渗流规律计算的压力变化要比拟线性情况平缓，更加符合低渗透油藏的开发实际。

Numerical simulation of the 3D oil-water phase dynamic permeability for low-permeability reservoirs

In view of nonlinear seepage characteristics during the flow of fluids in low-permeability reservoirs and the effect of the starting pressure gradient, the present paper established a mathematical model for the 3D oil-water phase seepage numerical simulation of reservoirs by integrating both nonlinear seepage and pseudo-linear seepage. The model for numerical simulation of low-permeability reservoirs was constituted by means of the fully implicit difference format and the preconditioned conjugated gradient method was applied to solve this model. The calculations of homogeneous reservoirs in the five-spot pattern and a certain block in the Daqing Oilfield indicated that the starting pressure gradient had a strong influence on the pressure distribution of low-permeability reservoirs. By the constant output, the greater the starting pressure gradient, the bigger the pressure variation and the larger the influenced area. Since the nonlinear flow formulation could describe both the flow behavior of fluids under a lower pressure gradient and the effect of the minimum starting pressure gradient in low-permeability reservoirs much better, the pressure calculated by the mathematical model using nonlinear flow formulation varied more gently than that using pseudo-linear flow formulation, thus, the model using nonlinear flow formulation is more practical for the exploration of low-permeability reservoirs.