多层压裂改造气井椭圆渗流压力动态特征

Pressure transient behavior of multi-layer fracturing gas wells with elliptical flow

郑荣臣 严谨 张郁哲 史文洋 程时清 王树平1

中国石化海相油气藏开发重点实验室，北京 100083 中国石油大学（北京）油气资源与探测国家重点实验室，北京 102249 中国石化华北油气分公司采气一厂，河南 郑州 450006

Key Laboratory for Marine Oil and Gas Exploration, SINOPEC, Beijing 100083, China State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China No.1 Gas Production Plant, North China Oil and Gas Company, SINOPEC, Zhengzhou 450006, China

椭圆流理论在垂直压裂井渗流方面应用广泛，但在多层压裂气井渗流方面缺乏研究。文中基于压裂改造SRV概念，建立了多层椭圆复合渗流模型，利用拉氏变换、马蒂厄方程和数值反演方法得到了解析解，绘制了压力典型曲线并划分了流动阶段。以双层储层为例，分析了分层边界组合、分层改造特征、层间储层差异特征对压力动态特征的影响规律。结果表明：双层压裂改造气井存在6个流动阶段，层间物性差异较小的双层压裂改造模型可用单层改造模型等效表征；各层改造程度相同时，改造范围差异增加，内外区过渡流阶段压力导数出现新的水平段；层间储层差异增大，过渡流阶段出现时间越早，压力导数上升越缓慢；原始地层压力差异主要影响表皮效应控制的早期过渡流阶段。

Elliptical flow theory is widely used in pressure transient analysis(PTA) for vertically fractured well, while it is rarely applied to multi-layer fractured gas wells. Based on the concept of stimulated reservoir volume(SRV) for fractured wells, a novel multi-layer elliptical composite model is presented in this paper. The Laplace integral transformation, Mathieu equation and numerical inversion algorithm are all introduced to obtain the solution in the real domain. We graphed the type curves on a log-log plot, and divided the typical flow regimes. Furthermore, we conducted sensitive analysis on boundary combination, fracturing features of each layer and reservoir interlayer-difference using double-layer reservoir as an example. The results indicate that there are mainly six flow regimes in double-layer fractured gas wells, and the double-layer model can be simplified into the single-layer model if both reservoir layers have the smaller difference. Pressure derivate curve will appear new horizontal line in the transition flow regime when the difference of fracturing volume increases under the same fracturing extent. Meanwhile, the transition flow regime occurs earlier, and the pressure derivative rises slower with the interlayer-difference increasing. The difference of initial pressure between both layers mainly affects the transitory regime from storage flow to radial flow.

10.6056/dkyqt202002014