压裂后页岩油藏多裂缝直井产能模型——以鄂尔多斯盆地页岩油井为例  

Study on productivity model for multiple-fracture vertical well in shale oil reservoirs after fractured:A case of shale oil wells in Ordos Basin

作　　者：董鹏 陈志明 于伟 DONG Peng;CHEN Zhiming;YU wei(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China;University of Texas at Austin,TX 78712,USA)

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]美国得州大学奥斯汀分校,美国得克萨斯州78712

出　　处：《大庆石油地质与开发》2022年第1期155-165,共11页Petroleum Geology & Oilfield Development in Daqing

基　　金：国家重点基础研究发展计划(973计划)“陆相致密油高效开发基础研究”(2015CB250900);北京市自然科学基金项目“页岩储层变导流能力裂缝网络井试井反演理论研究”(3204052)。

摘　　要：为提高单井产能和最终采收率,直井大型压裂技术已初步应用到鄂尔多斯盆地页岩油藏中。然而,经过大型压裂后,井筒附近会形成复杂多分支裂缝,这些复杂裂缝对大型压裂井的产能评价带来了挑战。针对此问题,基于页岩油藏和体积改造特点,建立了考虑渗透率应力敏感效应和非圆形边界的大型压裂复杂裂缝直井渗流模型,利用保角变换和Pedrosa替代法得到其解析产能模型,采用现有的常规裂缝井产能模型进行退化验证,并利用数值模拟方法和实例应用进一步验证。同时,分析了裂缝长度、裂缝导流能力、裂缝数目、应力敏感系数等因素对大型压裂直井产能的影响。结果表明:随着裂缝长度、裂缝导流能力及裂缝数目增大,大型压裂直井产能增大;随着应力敏感系数的增加,大型压裂直井产能下降;随着裂缝长度的增加,大型压裂直井产能变化明显;当裂缝导流能力和裂缝条数达到一定界限值时,随着裂缝导流能力、裂缝条数的增加,其对裂缝井产能影响减弱。因此,为在页岩油藏中获得最好的直井大型压裂效果,建议压裂裂缝尽可能长,不必追求过高的裂缝导流能力。In order to enhance individual well productivity and ultimate oil recovery,large-scale fracturing(LSF)technique for vertical well is primarily applied in shale oil reservoirs of Ordos Basin.However,complex fractures are usually generated near wellbore during LSF treatments,and these fractures bring a challenge in estimating the well productivity.To overcome the challenge,considering characteristics of shale oil reservoirs and volumetric stimulation,flow model for LSF vertical well with complex fractures is established considering stress-sensitivity effect of permeability(SEP)and non-circular boundary,and its analytical productivity model is obtained with the help of conformal transformation and Pedrosa’s substitution.Degradation verification is performed using existing productivity model of conventional fractured wells,and further verification is performed by numerical simulation and field application.At the same time,influence of some factors on LSF vertical well productivity are analyzed,including fracture length,fracture conductivity,fracture number,and SEP coefficient.The results show that productivity of LSF vertical well increases with increase of fracture length,fracture conductivity,and fracture number while decreases with increase of SEP coefficient.Productivity has much change as fracture length increases.When fracture number and conductivity increase to a certain value,with increase of fracture conductivity and number,the influence on fracture productivity gets less.Therefore,in order to obtain the best fractured effects of LSF vertical well in shale oil reservoirs,it is suggested that fractured lengths should be as long as possible and excessive high fracture conductivity is not necessary.

关 键 词：页岩油藏 大型压裂 非圆形边界 复杂裂缝 解析产能模型 

分 类 号：TE319[石油与天然气工程—油气田开发工程]