深层页岩裂缝扩展与多期次压裂实验研究——以渝西龙马溪组为例  

Experimental Study on Fracture Propagation and Multi-stage Fracturing ofDeep Shale:A Case of Longmaxi Formation in Western Chongqing

作　　者：王荣 刘伟[1] 朱炬辉 张然 陈明忠 钱思蓓 李建忠 刘爱 WANG Rong;LIU Wei;ZHU Juhui;ZHANG Ran;CHEN Mingzhong;QIAN Sipei;LI Jianzhong;LIU Ai(Downhole Operation Company,CNPC Chuanqing Drilling Engineering Co.,Ltd.,Chengdu,Sichuan 610051,China;School of Mechanical Engineering,Xihua University,Chengdu,Sichuan 610039,China;CNPC Chuanqing Drilling Engineering Co.,Ltd.,Drilling Fluid Technology Service Company,Chengdu,Sichuan 610039,China;Sichuan Yuesheng Oil and Gas Field Technical Service Co.,Ltd.,Chengdu,Sichuan 610066,China;Wumao Oil-pumping Operation Area of PetroChina Changqing Oilfield Company,Xi′an,Shaanxi 710018,China)

机构地区：[1]中国石油川庆钻探工程有限公司井下作业公司 [2]西华大学机械工程学院 [3]中国石油川庆钻探工程有限公司钻井液技术服务公司 [4]四川越盛油气田技术服务有限公司 [5]中国石油长庆油田公司武峁子采油作业区

出　　处：《钻采工艺》2024年第5期74-80,共7页Drilling & Production Technology

基　　金：国家自然科学基金区域创新发展联合基金“四川深层页岩气水平井缝网压裂填砂暂堵物理机制研究”(编号:U19A2043);中国石油集团川庆钻探公司科研课题“提升3500~4500 m页岩储层水力裂缝复杂程度和有效性工艺技术研究”(编号:CQ2021B-39-Z2-4);中国石油集团川庆钻探公司科研课题“大安区块页岩气水平井组压后裂缝评价与焖井排液一体化技术研究”(编号:CQ2023B-30-3-4);四川省自然科学基金项目“深层页岩气二氧化碳压裂-埋存的复杂裂缝形成能力研究”(编号:2022NSFSC1273)。

摘　　要：渝西深层页岩具有高闭合压力、高水平应力差的地质特征,导致页岩气开采过程中裂缝扩展难度大,裂缝扩展规律不清。本文以渝西深层页岩储层岩心力学参数、矿物质含量为基准,优选具有类似参数的川南龙马溪组页岩露头开展实验。通过模拟较高垂向应力和正断层应力状态,结合声发射监测数据与泵注压力数据,对不同天然裂缝发育条件下的岩页水力裂缝起裂和扩展规律进行研究分析。研究发现:正断层应力、天然裂缝不发育的条件下,压裂形成的裂缝形态单一;天然裂缝发育方位显著影响缝网形态,高角度天然裂缝引导人工裂缝转向,形成台阶状缝;水平天然裂缝引导人工裂缝水平扩展,形成“T”字或“工”字缝;声发射显示,在实验条件下水力裂缝破坏机理主要为拉张破坏,而水平天然裂缝破坏机理为剪切破坏;多期次压裂可有效改善缝间局部应力,进一步增加裂缝复杂程度;综上所述,天然裂缝是龙马溪深层页岩储层形成复杂缝网的基础条件。本文实验结果可为深层页岩气压裂中裂缝复杂度的提升措施提供实验规律认识和参考依据。The deep shale in western Chongqing has the geological characteristics of high closure pressure and high horizontal stress difference,which leads to the difficulty and unclear law of fracture propagation in the process of shale gas exploitation.Based on the core mechanical parameters and mineral content of deep shale reservoir in western Chongqing,this paper selects the shale outcrop of Longmaxi Formation in southern Sichuan with similar parameters to carry out experiments.By simulating high vertical stress and normal fault stress,combined with acoustic emission monitoring data and pumping pressure data,the initiation and propagation laws of hydraulic fractures in rock sheet under different natural fracture development conditions are studied.The results show that under the condition of normal fault stress and undeveloped natural fracture,the fracture form is single.The development orientation of natural fractures significantly affects the morphology of the fracture network,and the high angle natural fractures guide the artificial fractures to turn and form step-like fractures.Horizontal natural cracks guide artificial cracks to expand horizontally to form"T"or"work"cracks;Acoustic emission shows that under experimental conditions,the main failure mechanism of hydraulic fracture is tensile failure,while that of horizontal natural fracture is shear failure.Multi-stage fracturing can effectively improve the local stress between fractures and further increase the fracture complexity.To sum up,natural fractures are the basic conditions for the formation of complex fracture network in Longmaxi deep shale reservoir.The experimental results of this paper can provide a reference for the understanding of experimental rules and measures to improve fracture complexity in deep shale gas fracturing.

关 键 词：水力压裂 复杂缝网 深层页岩 天然层理缝 声发射 

分 类 号：TE377[石油与天然气工程—油气田开发工程]