摘要
页岩储层天然裂缝、水平层理发育,水力压裂过程中可能形成复杂的体积裂缝。针对页岩储层体积裂缝扩展问题,基于流-固耦合基本方程和损伤力学原理,建立了页岩储层水力压裂体积裂缝扩展的三维有限元模型。将数值模型的模拟结果与页岩储层裂缝扩展室内试验结果进行对比,二者吻合较好,从而证明了数值模型的可靠性。通过一系列数值模拟发现:(1)水力压裂过程中水平层理可能张开,形成水平缝,水平与垂直缝相互交错,形成复杂的体积裂缝网络;(2)水平主应力差增大,体积裂缝的分布长度(水平最大主应力方向压裂裂缝的展布距离)增加、分布宽度(水平最小主应力方向压裂裂缝的展布距离)减小,体积裂缝的长宽比增加;(3)压裂施工排量增大,体积裂缝的分布长度减小、宽度增加,压裂裂缝的长宽比降低;(4)天然裂缝的残余抗张强度增大,体积裂缝分布宽度减小、分布长度增加,体积裂缝的长宽比增加。研究成果可以为国内的页岩气的压裂设计和施工提供一定的参考和借鉴。
Due to the highly developed natural fractures and horizontal beddings in shale reservoirs, it is possible to generate complex volume fractures during hydraulic fracture treatment. In order to investigate the propagation process of complex fracture network, a three dimensional finite element model for volume fracture propagation of hydraulic fracture in shale reservoirs is built using fluid-solid coupling basic equations in porous medium and basic theory of damage mechanics. The numerical simulation results are in good accordance with laboratory experiment of shale fracture propagation, which prove the reliability of the numerical model. After a series of numerical simulations, some conclusions are drawn as follws：（1） The horizontal beddings can open and form horizontal fractures in hydraulic fracturing. They can intersect with vertical fractures and finally generate complex volume fracture network.（2） As the horizontal stress difference increases, the length of stimulated reservoir volume（SRV） can increase and the width can decrease, which means the ratio of length to width of SRV can increase. The length is the distribution distance of volume fracture along horizontal maximum principal insitu stress. The width is the distribution distance of volume fracture along horizontal minimum principal insitu stress.（3） As the pump rate of fracturing increases, the SRV length can decrease, width can increase, and the ratio of length to width of SRV can decrease accordingly.（4） When the residual tensile strength of the natural fracture becomes stronger, the width of SRV can decrease, the length and the ratio of length to width of SRV can increase. Research results can offer some references for hydraulic fracture design and operation of shale gas in China.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2015年第1期205-211,共7页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51304258)
"973计划项目"渝东南地区页岩气资源潜力评价(No.2012CB214705-05)
"863计划"页岩气勘探开发新技术(No.2013AA064503)
重庆市国土资源和房屋管理局科技计划项目(No.CQGT-KJ-2012-3)
关键词
页岩储层
天然裂缝
水平层理
裂缝扩展
体积裂缝
shale reservoir
natural fracture
horizontal bedding
fracture propagation
volume fracture
