川南深层页岩水力压裂缝网扩展规律数值模拟研究  

MODELING STUDY ON THE HYDRAULIC FRACTURING OF DEEP SHALE RESERVOIR IN SOUTHERN SICHUAN

作　　者：孙景行 曾波[2] 刘俊辰[2] 宋毅[2] 黄浩勇 姚志广 岳文翰 桂俊川 徐尔斯 张召彬 赫建明[3] SUN Jingxing;ZENG Bo;LIU Junchen;SONG Yi;HUANG Haoyong;YAO Zhiguang;YUE Wenhan;GUI Junchuan;XU Ersi;ZHANG Zhaobin;HE Jianming(School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China;Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国矿业大学(北京),力学与建筑工程学院,中国北京100083 [2]中国石油西南油气田分公司页岩气研究院,中国成都610051 [3]中国科学院地质与地球物理研究所,中国科学院页岩气与地质工程重点实验室,中国北京100029

出　　处：《工程地质学报》2022年第4期1193-1202,共10页Journal of Engineering Geology

基　　金：中国石油天然气集团有限公司重大现场试验项目“深层页岩气有效开采关键技术攻关与试验-深层页岩气体积压裂技术现场试验”(资助号:2019F-31);中国石油天然气股份有限公司重大专项“西南页岩气体积改造技术提升攻关与现场试验”(资助号:2021CGCGZ005)。

摘　　要：3500 m以深页岩气资源量占整个川南地区总资源量的比例高达86.5%,该区深层页岩气藏构造复杂,压裂形成复杂缝网的难度大,有必要通过数值模拟研究深层页岩气复杂缝网主控因素,对实现川南地区深层页岩气的效益开发具有重要意义。在对川南地区页岩气气田某井的岩芯进行细观尺度下的观察并构建二维裂缝模型的基础上,利用位移间断边界元法(DDM)模拟深层页岩水力压裂过程中水力裂缝与天然裂缝相互作用的物理力学过程,研究主应力、应力差和压裂液排量对裂缝扩展的影响。结果表明:在高应力差条件下缝网的复杂程度和总长度急剧降低,缝网的平均宽度增大,且平均宽度随排量增加而增大的能力变得有限。在高应力差条件下提升压裂液排量,缝网长度的增加以产生新生裂缝为主,同时提升排量对于激活天然裂缝有一定的提升作用,但是效果有限。相比于拉张裂缝,剪切裂缝的形成受主应力和压裂液排量的影响更显著,在高应力差条件下缝网中剪切裂缝的长度急剧降低。随着压裂液的注入,在较低应力差和相同压裂液注入量的情况下,低排量工况下的裂缝长度逐渐大于高排量工况下的裂缝长度。在应力差较高的情况下裂缝扩展的速率较低,同时会使提升排量而形成更多新生裂缝的能力变得有限。基于显微镜观察构建的裂缝模型计算出的结果能够较好地符合场地实际,为深层水力压裂设计和施工提供参考。Based on the observation of the core of a well in the shale gas field in southern Sichuan at the mesoscale and the construction of a two-dimensional fracture model,displacement discontinuity method was used to simulate the physical and mechanical process of the interaction between hydraulic fractures and natural fractures in deep shale hydraulic fracturing.The influence of principal stress,stress difference and fracturing fluid injection rate on fracture propagation were discussed.The results show that under high stress difference,the length of the fracture decreases,the average width of the fracture increases and the increasing of fracture average width due to the increase of injection rate becomes limited.New fractures prevail in the increase of fracture length with the injection rate increases,so as to improve the activation of natural fractures,but the effect is limited.The generation of shear fracture is more affected by principal stress and injection rate,and its length decreases significantly under high stress difference.The fracture length under low injection rate is gradually larger than that under high injection rate during the fracturing process,under the condition of lower stress difference and the same injection volume.Fracture propagation rate decreases under high stress difference and generating more new fractures due to increasing the injection rate becomes limited.The modeling results based on the microscope observation meet the actual site better,and provide a reference for the design and construction of deep hydraulic fracturing in shale gas reservoir.

关 键 词：位移间断边界元法 数值模拟 水力压裂 页岩储层 

分 类 号：P642.3[天文地球—工程地质学]