油气藏评价与开发
第7卷第5期2017年10月
RESERVOIR EVALUATION AND DEVELOPMENT
页岩气水平井分段压裂复杂缝网形成机制
许文俊，李勇明，赵金洲，陈曦宇，彭瑀
（西南石油大学油气藏地质及开发工程国家重点实验室，四川成都610500）
摘要：水平井分段压裂是页岩气高效开发的重要技术手段，有意识地利用水力裂缝沟通页岩储层中的天然裂缝，使其闭合的部分重新开启，开启的部分又相互连通，从而在地层中形成具有较大规模的复杂裂缝网络，有利于实现地层中页岩气向井筒的高效流动。为了合理优化页岩储层压裂设计方案，提高页岩储层压裂改造效果，需先认清页岩水平井分段压裂复杂缝网形成机制。基于位移不连续理论，建立了水平井分段压裂多裂缝干扰模式下的地应力场模型，分析了天然裂缝在复杂地应力场和存在压裂液滤失作用的情况下，发生张开或剪切破裂形成复杂缝网的机理。分析表明：水力裂缝诱导应力虽能降低地层原始水平应力差，但也会增加地层中天然裂缝发生张开和剪切破裂的难度，不利于复杂裂缝网络的形成。压裂液滤失是导致地层中天然裂缝发生张开和剪切破裂形成复杂裂缝网络的关键因素，天然裂缝的剪切破裂区域要远大于张开破裂区域，多条水力裂缝滤失效应的叠加更有利于形成具有较大波及区域的复杂裂缝网络。充分考虑压裂液滤失对复杂裂缝网络形成的影响，对提高页岩气水平井分段多簇压裂改造效果具有重要意义。
关键词：分段压裂；位移不连续理论；剪切破裂区域；张开破裂区域；复杂缝网
中图分类号:TE357文献标识码:A
Formation mechanism of complex fracture network under horizontal well staged
fracturing in shale gas reservoir
Xu Wenjun,Li Yongming,Zhao Jinzhou,Chen Xiyu and Peng Yu
(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan
610500,China)
Abstract:Horizontal well staged fracturing is an important technology for shale gas production,whose essence is to use hydraulic fracture to activate natural fractures.The natural fractures can make closed parts reopen and opened parts interconnect,and then form complex fracture network in shale reservoirs,accordingly,shale gas will flow to the wellbore through complex fracture network efficiently.In order to optimize shale reservoir fracturing design and improve the effects of shale reservoir fracturing,it is necessary to fully understand the formation mechanism of complex fracture network in staged fractured shale horizontal wells.Based on the displacement discontinuity theory,a complex stress field calculation model which takes into consideration hydraulic fracture inter⁃ference is established,which analyzes the mechanism that natural fractures occur open and shear fracture,and then the complex fracture network under the circumstance of complex ground stress field and fracturing fluid leak-off was formed.The results demon⁃strate that although the hydraulic fracture induced stress field can reduce the original horizontal stress difference,it would also in⁃crease the difficulty of natural fractures opening and shearing,which is unbeneficial for the formation of complex fracture network. Moreover,it is attained that fracturing fluid leak-off is the key factor that leads to the open and shear fracture of natural fractures in the formation of complex fracture network and the shear rupture zone of natural fractures is much larger than the open rupture zone, furthermore,the superposition of multiple hydraulic fracture filtration effect is more favorable for the formation of complex fracture network with a larger spread area.The impacts of fracturing fluid leak-off on complex fracture network have important significance for improving staged fracturing transformation of shale horizontal wells.
Key words:staged fracturing,displacement discontinuity theory,shear rupture zone,open rupture zone,complex fracture network
收稿日期：2016-10-31。
第一作者简介：许文俊（1991—），男，在读博士研究生，油气田增产改造理论与技术方面的研究。
基金项目：国家自然科学基金重大项目“页岩地层动态随机裂缝控制机理与无水压裂理论”（51490653）；国家重点基础研究发展计划“中国南方海相页岩气高效开发的基础研究”（2013CB228004）。
