矩形油藏多段压裂水平井不稳态压力分析

Transient pressure analysis of multiple-fractured horizontal wells in boxed reservoirs

通过确定导流能力影响函数,给出了有限导流垂直裂缝井不稳定渗流的新解析解。再利用叠加原理得到了带有多条有限导流垂直裂缝的压裂水平井不稳定压力分布。计算结果表明,理想模式下渗流方式发生的顺序是早期双线性流动→早期线性流动→中期径向流动→中期线性流动→晚期拟稳态流动;均匀分布等导流裂缝缝长的不均匀性主要影响早期双线性流动和线性流动阶段的转换时期,加快中期径向流动的出现;等长等导流裂缝分布的不对称性主要影响中期线性流动阶段,不对称性越强,受矩形地层各条边界的影响越明显;等长均布裂缝导流能力的强弱主要影响早期双线性流动和线性流动阶段,导流能力的差异使得早期双线性流动持续时间变短而线性流动持续时间相对增加;等长等导流均布裂缝条数增加,储集层整体压力降落加快,中期径向流段持续时间变短而中期线性流段延长,而裂缝长度相对增加,中期径向流段持续时间变短而中期线性流段可能不出现,说明压裂水平井具分段改善渗流方式的特点。

A new analytical solution of fluid unsteady flow was presented for wells with finite-conductivity vertical fractures by determining impact functions of fracture conductivity. Based on the new solution, the transient pressure distribution of a fractured horizontal well with multiple finite-conductivity vertical fractures was obtained using the principle of superposition. Calculation results show the pressure transient behavior of fractured horizontal wells under the condition of constant bottom rate. In the ideal fracture arrangement, flow patterns occur in the order of early bilinear flow → early linear flow→ middle radial flow→ middle linear flow late pseudo steady state. Uneven length of fractures with equal conductivity and uniform arrangement may affect the transform of early linear flows from earlier bilinear flows and the premature birth of middle radial flows. Nonuniform arrangement of fractures with even length and equal conductivity may influence middle radial flows. Different conductivity of fractures with equal length and uniform arrangement shortens the period of bilinear flows and lengthens the linear flows. Increase in the number of fractures with even length, equal conductivity and uniform arrangement accelerates pressure drops in the reservoir, shortens the period of middle radial flows and lengthens the middle linear flows. Increase in length of all fractures shortens the period of middle radial flows and may result in absence of radial flows. It is demonstrated that the horizontal well with multiple vertical fractures may improve fluid flow patterns.