致密储层垂直裂缝井压力动态特征

Dynamic Pressure Behavior in Vertically Fractured Wells of Tight Reservoir

针对致密储层非达西渗流规律及垂直裂缝井的特殊流动模式，采用考虑井筒存储和裂缝表皮的三线性流模型描述早、中期流动阶段及考虑启动压力梯度的有效井径模型反映晚期拟径向流阶段。通过三线性流模型和有效井径模型的优化组合，建立了致密储层垂直裂缝井不稳定渗流试井分析模型，采用最小二乘法拟合三线性流模型与有效井径模型的压力解。分析了无量纲导流系数、裂缝表皮及启动压力梯度对井壁压力及压力导数动态曲线的影响，结果表明：无量纲导流系数越大，压力降越小，从而能量损耗越小；裂缝表皮主要影响早、中期压力动态；启动压力梯度越大，后期无量纲压力增加越明显，说明渗流过程能量损失增大。

For non-Darcy flows of fight reservoir and special flow patterns in vertically fractured well, a trilinear flow model is developed to study the early-time and immediate-time flow stages, taking the effect of wellbore storage and the skin effect of vertical fracture into consideration. The effective wellbore radius is used to describe the effect of the threshold pressure gradient in the latter time flow regime. Combining the trilinear flow model with the effective wellbore radius, a transient flow well-testing model in tight reservoir is built, which is solved by the least squares method. At the same time, an analysis is made based on these solutions that include the effects of various parameters, such as the fracture conductivity, the skin on the fracture, and the threshold pressure gradient. It is shown that the larger the dimensionless fracture conductivity and the smaller the pressure drop, the smaller the energy loss will be; the pressure response in early- time and intermediate-time stages is mainly influenced by the skin factor; the larger the threshold pressure gradient and the more significant the dimensionless pressure increase, the larger the energy loss will be in the later stage.