含X型裂隙类岩石材料水力裂缝扩展研究  

Hydraulic fracture propagation of rock-like material with X-type flaws

作　　者：张波[1] 郭帅 杨学英[3] 李垚 许新骥[4] 杨磊[4] 张柏楠 ZHANG Bo;GUO Shuai;YANG Xueying;LI Yao;XU Xinji;YANG Lei;ZHANG Bonan(School of Civil Engineering,Shandong University,Jinan250061,China;Jining Construction Engineering Quality and Technology Center,Jining 272000,China;Shandong Urban Construction Vocational College,Jinan 250014,China;Research Center of Geotechnical and Structural Engineering,Shandong University,Jinan 250061,China)

机构地区：[1]山东大学土建与水利学院,山东济南250061 [2]济宁市建设工程质量技术中心,山东济宁272000 [3]山东城市建设职业学院,山东济南250014 [4]山东大学岩土与结构工程研究中心,山东济南250061

出　　处：《煤炭学报》2019年第7期2066-2073,共8页Journal of China Coal Society

基　　金：国家自然科学基金面上资助项目(51879151,51509146),国家自然科学基金重点资助项目(51739007)

摘　　要：页岩气等非常规油气资源逐渐成为资源开采的热门领域。提高非常规油气藏的渗透率是目前面临的突出问题,水力压裂技术是当前提高非常规油气藏渗透率主要技术手段之一。为探究天然岩体中的X型裂隙对水力裂缝扩展规律的影响,采用真三轴水压加载系统,对含预置X型裂隙的类岩石试件进行了水力压裂实验,研究了多种X型裂隙形态在不同围压下对水力裂缝扩展的影响,并使用数值计算软件Abaqus中的扩展有限元(XFEM)方法对部分实验工况进行了数值模拟。研究结果表明:X型裂隙裂尖位置对水力裂缝的扩展有诱导作用,水平应力差系数越低,天然裂隙裂尖对水力裂缝扩展方向的诱导作用越强;随着水平应力差系数的增大,裂尖位置对水力裂缝扩展的诱导作用减弱,水力裂缝逐步向水平最大主应力方向扩展。主、次裂隙裂尖距离较近时,两裂尖所处位置的应变能密度较大,主、次裂隙裂尖对水力裂缝扩展诱导具有集中强化效应,水力裂缝更易向裂尖位置扩展;主、次裂隙裂尖处于近似关于水平最大主应力方向对称的位置,主、次裂隙裂尖的应变能密度比较接近,主、次裂隙裂尖对水力裂缝扩展诱导作用具有平衡弱化效应,裂尖对水力裂缝的诱导作用减弱,水力裂缝更易向水平最大主应力方向扩展。Unconventional oil and gas resources such as shale gas have gradually become a hot area for resource exploitation.Low permeability of unconventional oil and gas reservoirs is one of prominent problem in oil/gas exploitation.Hydraulic fracturing technology is one of main technical means to improve the permeability of oil/gas reservoirs.In order to explore the influence of X-type flaws on hydraulic crack propagation in natural rock mass,the hydraulic fracturing experiments on rock-like material with pre-existing X- type flaws are carried out with the true triaxial hydraulic loading system.The influences of X-type flaws position on hydraulic fracture propagation are studied under different horizontal stresses.Some experimental conditions are numerically simulated using the extended finite element method (XFEM) method with the calculation software Abaqus.The testing results show that the X- type flaw tip position may influence hydraulic fracture propagation.The lower the horizontal stress difference,the more easily the X-type flaw tips may induce the hydraulic fracture propagates towards flaw tip position.With the increase of horizontal stress difference,the inducing role of X-type flaw tips on hydraulic fracture propagation may decrease.The hydraulic fracture gradually propagates towards the maximum horizontal stress direction.When the main and secondary flaw tips are close,the strain energy density at the location of the two flaw tips is larger than that of other places.In this situation the flaw tip has induction strengthening effect on hydraulic fracture propagation,and the hydraulic fracture is more likely to propagate to the flaw tip.When the main and secondary flaw tips are approximately symmetrical about the horizontal maximum principal stress direction,the strain energy density of the main and secondary flaw tips are almost same.In this situation the induction effect of the main and secondary flaw tips on hydraulic fracture is weakened,and the hydraulic fracture is more likely to propagate toward the maximum

关 键 词：水压致裂 X型裂隙 裂尖位置 水力裂缝扩展 

分 类 号：TD315[矿业工程—矿井建设]