School of Mines, China University of Mining and Technology
College of Petroleum Engineering, China University of Petroleum (Beijing)
Shale Gas Research Institute, PetroChina Southwest Oil & Gasfield Company
Sinopec Petroleum Exploration and Production Research Institute

页岩气/ 煤层气压裂井缝网反演是开发调整部署、提采方案优选与效果评价的基本依据,但储层天然裂缝发育,压裂缝网形态复杂、非均质性强,现有试井方法难以有效反演。 在表征页岩气/ 煤层气赋存、非线性流动机理、不同尺度非均质缝网的基础上,建立了压裂井多介质渗流数学模型,基于改进格林元方法实现了模型的高效数值求解,获得了页岩气/ 煤层气压裂井的压力动态响应特征,明确了流动阶段与非均质缝网参数的影响规律,构建了非均质缝网参数的试井反演方法,并结合现场案例进行了应用研究。 结果表明:页岩气/ 煤层气压裂井压力动态响应主要展示出6 个流动阶段,考虑储层分区后会出现改造区拟稳态流动阶段;裂缝导流能力主要影响早期双线性与线性流阶段,裂缝长度对边界控制流之前的阶段均有较大影响;相同裂缝长度与压裂段数下,缝网形态的压力动态响应较弱,需要联合地质、压裂、微震监测等资料才能反演缝网非均质性;所提出的试井分析方法综合了缝网建模、动态模拟、特征线/ 图版拟合等过程,可以实现压裂井非均质缝网反演,为页岩气/ 煤层气气藏工程研究提供了理论基础与技术支持。

Fracture networks inversion for shale gas/ coalbed methane fractured wells is the basis for de-velopment-adjustment-deployment, scheme optimization and efficiency evaluation of enhanced gas re-covery. However, existing well-testing methods face challenges in efficient fracture inversion consideringlimitations from: abundant natural fractures development in the formation, complex pattern of the frac-tured networks and profound heterogeneities. This study established a multi-media seepage mathematicalmodel of fractured wells based on the characterization of shale gas/ coalbed methane occurrence, nonlin-ear flow mechanism and varied scales of heterogeneous fracture networks. Afterward, the high-efficientnumerical solution of the model was achieved based on the improved Green's element method, and thedynamic pressure response characteristics of fractured shale gas/ coalbed methane wells were obtained.Then the influence law between flow phases and heterogeneous fracture network parameters wasclarified. At last, a well-testing data analysis method for inversing the heterogeneous fracture networkparameters was raised and relevant applications were applied to a field case. The results showed that thepressure dynamic response of fractured shale gas/ coalbed methane well mainly consisted 6 flow stages.The pseudo-steady flow stage would appear in the modified zone if reservoir zoning were considered.Early bilinear and linear flow phases were primarily affected by fracture conductivity, while phases be-fore the boundary-dominated flow phase were heavily impacted by fracture length. Fracture networkmorphology's dynamic response under pressure could be weak if fracture length equaled fracture stages,then other data should be introduced to obtain the heterogeneity of the fracture networks, such as geolo-gy, fracturing, microseismic monitoring data, etc. By combining fracture network modeling, dynamicsimulation, and characteristic line / curve fitting, the proposed well-testing analysis method can be usedto interpret heterogeneous fracture networks in fractured wells. In this study, basic theory and technicalsupport are provided for the research of shale gas/ coalbed methane reservoir engineering.

国家自然科学基金项目(51974328);江苏省自然科学基金青年项目(BK20210520);中国博士后科学基金项目(2022M713372)

1 气体赋存/流动机理与非均质缝网表征
1.1 气体高压物性表征
1.2 气体赋存机理表征
1.3 气体流动机理表征
1.4 非均质缝网表征
2 压裂井多介质渗流数学模型
2.1 基质渗流模型
2.2 微裂缝渗流模型
2.3 离散裂缝渗流模型
2.4 模型求解
1) 模型进行Laplace变换处理：
2) 建立边界积分方程：
3) 基质-裂缝网格剖分：
4) 数学模型的数值离散：
5) 数值模型迭代求解：
3 结果分析
3.1 流动阶段分析
1) 复杂缝网-单区域模型
2) 复杂缝网-分区模型
3.2 压力动态响应影响因素分析
1) 裂缝导流能力
2) 裂缝形态
3) 裂缝长度
4) 井储和表皮效应
5) 改造区渗透率提高倍数
6) 改造区大小
3.3 缝网参数试井反演方法
1) 特征线拟合法
① 早期井筒储集阶段
② 双线性流阶段
③ 线性流阶段
2) 缝网参数试井反演流程
3.4 现场应用
4 结 论