考虑井网格影响的油水两相低渗油藏数值模拟

摘要

A mathematical model for numerical simulation of 3D water-oil two phase reservoir is established with consideration of the influence of start-up pressure gradient,and the inner boundary conditions are derived based on the pseudo stable seepage theory,in the process of which fixed flow pressure,fixed oil production rate and fixed liquid production rate are taken into consideration. Then by full implicit finite difference scheme,corresponding numerical model is established and solved by pretreatment conjugate gradient method. The calculation results show that start-up pressure gradient has obvious effect on pressure field in low permeability reservoirs;in case of fixed oil production,the bigger start-up pressure gradient is,the more severely pressure changes and the larger pressure drop range is. The effect of well-grid conditions on pressure field is not obvious,but its effect on well flow pressure is obvious;in case of fixed oil production rate,with the increase of start-up pressure gradient well flow pressure drops.%考虑流体在低渗透油藏流动过程中启动压力梯度的影响，建立了三维油水两相油藏数值模拟数学模型；基于拟稳定渗流理论，推导了考虑启动压力梯度影响的油藏数值模拟定井底压力、定产油量和定产液量条件下的内边界条件；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。计算结果表明，启动压力梯度对低渗透油藏的压力场有明显的影响，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。井-网格条件对油藏压力场的影响不明显，但对井底压力影响较大，定产条件下，启动压力梯度越大，则井底流压越低。