摘要
为明确地应力差、排量以及压裂级数对页岩水平井分段压裂裂缝扩展的影响规律,基于真三轴水力压裂试验系统,以露头页岩试样(300 mm×300 mm×300 mm)为研究对象,结合分段压裂裂缝诱导应力检测和水力压裂试验后试件裂缝三维形态结构新方法,在最大水平应力>垂直应力>最小水平应力条件下,开展页岩露头水平井多级压裂试验研究,探究地应力差、泵注排量和压裂级数对页岩水平井分段多级压裂裂缝扩展的影响规律.研究表明:由于上覆应力低于最大水平主应力,且水平应力差(数值等于最大水平应力减去最小水平应力)不变,上覆应力的减小易导致层理缝的开启;水平应力差越大,产生的横切井筒水力裂缝扩展距离越远;小排量下净压力低,压裂液易滤失,不易产生深穿透的主裂缝;压裂级数少的缝间干扰弱,能够开启相应级数的水力裂缝;地应力状态影响着层理缝及岩样的压实,上覆应力低时,压裂液易渗入层理缝,诱导应力值较小,且较为波动.结合泵注压力曲线和诱导应力曲线能更准确地了解水力压裂裂缝扩展的过程,推进对水平井多级分段压裂裂缝扩展规律的深入研究.
In order to clarify the influence of in-situ stress difference, displacement and fracturing series on the propagation of staged fractures in shale horizontal wells, we do the research based on a true triaxial hydraulic fracturing test system, using outcrop shale samples(300 mm × 300 mm × 300 mm) as the research object, combined with the new method of fracture-induced stress detection of staged fracturing and the three-dimensional morphological structure of specimens after hydraulic fracturing test. On the condition of maximum horizontal stress >vertical stress > minimum horizontal stress, we carry out the page multi-stage fracturing test study of horizontal wells in rock outcrops, to explore the influence of in-situ stress difference, pumping displacement and fracturing series on the fracture propagation of staged multi-stage fracturing in shale horizontal wells. The research results show that:because the overburden stress is lower than the maximum horizontal principal stress, the horizontal stress difference(the value is equal to the maximum horizontal stress minus the minimum horizontal stress) remains unchanged, and the reduction of the overburden stress easily leads to the opening of the bedding joints;the greater the horizontal stress difference is, the farther the propagation distance of the cross-cutting wellbore hydraulic fracture is;the net pressure is low under small displacement, the fracturing fluid is easy to filter out, and it is not easy to produce deeppenetrating main fractures;the interference between fractures with fewer fracturing stages is weak and can open hydraulic fractures of the corresponding series;the state of in-situ stress affects the compaction of bedding fractures and rock samples. When the overlying stress is low, the fracturing fluid is easy to penetrate into the bedding fractures,and the induced stress value is small and fluctuates greatly. Combined with the pump injection pressure curve and the induced stress curve, we can more accurately undersand the process of hydraulic fracturing fracture propagation.The research results of this article can promote the in-depth study of the fracture propagation law of multi-stage staged fracturing in horizontal wells.
作者
郭天魁
孙悦铭
刘学伟
陈铭
刘晓强
GUO Tiankui;SUN Yueming;LIU Xuewei;CHEN Ming;LIU Xiaoqiang(School of Petroleum Engineering,China University of Petroleum(East China),Qingdao 266580,Shandong Province,P.R.China;China Petroleum Engineering Research Institute of Dagang Oilfield Company,PetroChina,Tianjin 300280,P.R.China)
出处
《深圳大学学报(理工版)》
CAS
CSCD
北大核心
2022年第2期111-118,共8页
Journal of Shenzhen University(Science and Engineering)
基金
山东省自然科学基金省优青资助项目(ZR2020YQ36)
山东省自然科学基金资助项目(ZR2019QEE005)。
关键词
油田开发
页岩储层
提高采收率
水平井分段压裂
裂缝扩展
诱导应力
物理模拟试验
oilfield development
shale reservoir
enhanced oil recovery
staged fracturing of horizontal well
fracture propagation
induced stress
physical simulation test