多孔眼裂缝竞争起裂与扩展数值模拟  

Numerical simulation of multi-hole fracture competition initiation and propagation

作　　者：赵金洲[1] 王强[1] 胡永全[1] 任岚[1] 傅成浩 赵超能 ZHAO Jin-zhou;WANG Qiang;HU Yong-quan;REN Lan;FU Cheng-hao;ZHAO Chao-neng(State Key Laboratory of Oil-Gas Reservoir Geology&Exploitation,Southwest Petroleum University,Chengdu 610500,China;Sinopec Jianghan Oilfield Oil and Gas Production Engineering and Technical Service Center,Qianjiang 433124,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室·西南石油大学,四川成都610500 [2]中国石化江汉油田采油气工程技术服务中心,湖北潜江433124

出　　处：《天然气地球科学》2020年第10期1343-1354,共12页Natural Gas Geoscience

基　　金：国家科技重大专项“涪陵页岩气开发示范工程”(编号:2016ZX05060)资助.

摘　　要：射孔是水力压裂作业成功实施的关键因素之一,射孔参数研究对于储层改造、油气开采具有重要意义。基于全局嵌入黏聚区域模型(Cohesive Zone Model),建立了模拟多孔眼裂缝起裂、扩展的有限元模型。模型把储层考虑为致密、低渗透性的孔弹性介质,耦合了裂缝中流体流动与地质应力间的相互作用。KGD解析解与模拟结果保持吻合,验证了黏聚区域模型的准确性。研究结果表明多孔眼起裂会表现出4种竞争起裂模式:第一,初期就起裂并维持张开;第二,孔眼张开但未曾起裂;第三,初期起裂扩展后又闭合;第四,初期未起裂中后期才起裂。随着射孔密度的增加,孔眼的起裂率和平均破裂压力逐渐降低,近井筒区域裂缝复杂度增加。随着排量与黏度的增加,孔眼的初始起裂率、形成的主裂缝以及微裂缝数量都呈增加的趋势,水平应力差的影响则与之相反。多个射孔孔眼存在时,裂缝通过合并或闭合的方式呈现出由复杂到简单的变化,裂缝数量表现出由多到少的变化,最终形成以2~4条主裂缝为主(按孔眼起裂形成的主缝数进行统计),微裂缝为辅的扩展模式。Perforation is the key to the successful implementation of hydraulic fracturing,and the study of perfo⁃ration parameters is of great significance for reservoir reconstruction and oil and gas exploitation.Based on the global embedded cohesive zone model,a finite element model is established to simulate the initiation and propa⁃gation of multi-hole fractures.In the model,the reservoir is considered as a dense,low-permeability porous elas⁃tic medium,and the coupling effect of fluid and geomechanics during fracturing are considered.The KGD ana⁃lytical solution is consistent with the simulation results,which verifies the accuracy of the cohesive zone model.The results show that there are four competitive modes for multi-hole crack initiation.Firstly,the cracks open at the beginning and remain open;Secondly,the hole is open but not cracked;Thirdly,the initial initiation ex⁃tends and then closes;Finally,the initial crack did not start in the late crack.With the increase of perforation density,the perforation initiation rate and average fracture pressure gradually decrease,and the fracture com⁃plexity in the near-wellbore area increases.With the increase of displacement and viscosity,the initial crack rate,the number of main cracks and microcracks formed in the hole tend to increase,while the influence of hori⁃zontal stress difference is opposite.In the presence of multiple perforating holes,the crack propagation presents a change from complex to simple,and the number of cracks presents a change from more to less,Statistics are made according to the number of main hydraulic fractures formed at the perforation.The expansion mode is formed with 2-4 main cracks and micro cracks as auxiliary.

关 键 词：裂缝扩展 射孔密度 水力压裂 竞争起裂 黏聚区域模型 

分 类 号：TE371[石油与天然气工程—油气田开发工程]