考虑启动压力梯度低渗透油藏应力敏感模型研究

Numerical model considering threshold pressure gradient for stress-sensitive low permeability reservoir

在运动方程中加入启动压力梯度,考虑地层渗透率随压力的变化而变化,建立了应力敏感带启动压力梯度均质低渗透油藏试井解释模型。应用预估校正法对所形成的非线性抛物型方程进行线性化,采用追赶法进行求解。参数敏感性分析表明,启动压力梯度和渗透率变化模数对压力及压力导数存在较大影响,导致径向流段消失,表现为压力及压力导数曲线后期上翘。在试井解释中考虑启动压力梯度和渗透率变化模数的影响可使低渗透油藏试井解释结果更接近生产实际,为油藏开发提供理论依据。

A well test interpretation model has been established for stress-sensitive,homogeneous,low permeability reservoirs by adding threshold pressure gradient to kinematic equation and considering the change of permeability with pressure.The nonlinear parabolic equation thus formed is linearized through proofread-correct method and is solved by LU decomposition.Analysis of parameter sensitivity shows that threshold pressure gradient and permeability modulus have strongly affected pressure and the differential of pressure,resulting in radial flow section disappeared,showing tilting of pressure and the differential of pressure curve in later section.The result of well test interpretation of low permeability reservoirs is more practical with consideration of threshold pressure gradient and permeability modulus.