页岩气藏压裂水平井不稳定渗流模型及试井分析

Transient flow model of multiply fractured horizontal wells in shale gas reservoirs and well test analysis

 雷宇 曾彦 宁正福

北京石油机械有限公司，北京 102206 中国石油大学（北京）石油工程教育部重点实验室，北京 102249 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

Beijing Petroleum Machinery Co., Ltd., Beijing 102206, China MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China

 页岩气藏基质渗透率极低，因此多采用压裂直井或压裂水平井进行开发。页岩气藏多级压裂水平井压力动态研究是获取页岩储层参数的重要手段之一，也是页岩气井产能评价的基础。然而，目前的压裂水平井模型忽略了页岩气藏的非均质性和页岩有机质纳米孔隙中的渗流机理，未考虑不同赋存空间气体流动特征的差异性。为此，文中建立了页岩气藏多级压裂水平井压力动态解析模型。基于五线性流模型，将储层分为2个上部储层区域、2个内部储层区域及人工裂缝区域。分析不同区域流动特征，并运用Laplace变换和正规摄动方法对模型进行求解。根据模型解析解绘制压力动态曲线，并进行流动区域划分和敏感性分析。研究结果表明，该模型与实际生产数据吻合度较高，具备可靠的理论支撑，能较好地描述页岩气井开发过程中的压力动态变化。

 The matrix of shale gas reservoirs has an extremely low permeability; therefore, fractured vertical wells and multi-stage fractured horizontal wells (MFHWs) are adopted in most cases for exploration purpose. In this context, studying the dynamic pressure in MFHWs in shale gas reservoirs not only provides an important means of obtaining the parameters of shale reservoirs, but also constitutes the basis of evaluating the productivity of shale gas wells. However, existing models for fractured horizontal wells have neglected the heterogeneity of shale gas reservoirs and the seepage mechanism in the nanopores of shale organic matter, and failed to take into account the differences of gas flow characteristics among different occurrence spaces. On that account, in this study, we established a dynamic pressure analysis model considering reservoir heterogeneity and stress sensitivity effect of MFHWs on shale gas reservoirs. Based on the five-linear flow model, this study divides one reservoir into two top reservoir regions, two inner reservoir regions and one artificial fracture region. Through analyzing the flow characteristics of different regions, it uses Laplace transformation and regular perturbation methods to solve the model; based on the analytical solution to this model, it plots the dynamic pressure curve and carries out flow region division and sensitivity analysis. As indicated by the study results, the model established in this study fits relatively well with actual production data, has a reliable theoretical foundation, and can preferably describe the dynamic changes of pressure in the exploration process of shale gas wells.

10.6056/dkyqt201804015