摘要
页岩油气高效开发需要对储层进行大规模压裂改造,水力裂缝垂向扩展激活纹层弱面是形成复杂压裂缝网的关键。然而,由于海相页岩与陆相页岩沉积环境、矿物成分和岩体结构存在显著差异,导致水力压裂效果差异较大,亟需对水力裂缝扩展规律进行深入探索。本文选取了龙马溪海相页岩和长7段陆相页岩,开展了力学特性试验和真三轴应力状态下水力裂缝扩展规律研究。分析了海相页岩和陆相页岩力学各向异性、注入压力曲线、压裂缝网形态与裂缝扩展过程的声发射能量。结果表明:(1)海相页岩力学强度和弹性模量明显高于陆相页岩,抗压强度相差61.4~102.2 MPa,抗拉强度差值约为1.7~2.6 MPa,弹性模量差值约为7.0~25.7 GPa,表明层理弱面对陆相页岩力学特性和破裂模式影响更为显著。(2)海相页岩破裂压力和声发射能量高于陆相页岩,水力裂缝起裂和扩展特征明显。陆相页岩注入压力曲线明显不同于海相页岩,压裂液沿层理缝滤失,造成注入压力曲线非线性增长。陆相页岩水力裂缝起裂和主破裂特征不明显,声发射能量较低。(3)海相页岩水力裂缝形态较为平直,射孔起裂后形成两条主裂缝。陆相页岩水力裂缝形态曲折,垂向扩展受到层理弱面抑制,裂缝高度较小。当压裂液黏度由60 MPa·s增大至240 MPa·s时,陆相页岩水力裂缝垂向扩展高度增大,裂缝形态更加复杂。
The efficient development of shale oil and gas requires large-scale fracturing of the reservoir,and the vertical expansion of hydraulic fractures to activate the weak surface of the laminate is the key to form a complex fracture network.However,due to the differences in sedimentary environment,mineral composition and rock mass structure between marine shale and continental shale,the effectivities of hydraulic fracturing vary significantly,and it is urgent to further explore the propagation law of hydraulic fractures.In this paper,Longmaxi marine shale and Chang 7 member continental shale were selected to conduct mechanical property tests and hydraulic fracture propagation characteristics under true triaxial stress.The mechanical anisotropy,injection pressure curve,fracture network geometry and acoustic emission activity of marine shale and continental shale were investigated.The results show that:(1)The mechanical strength of marine shale is significantly higher than continental shale,the compressive strength difference is 61.4~102.2 MPa,the tensile strength difference is about 1.7~2.6 MPa,and the elastic modulus difference is about 7.0~25.7GPa,indicating that the weak bedding has a more significant influence on the mechanical properties and fracture pattern of continental shale.(2)The breakdown pressure and acoustic emission energy of marine shale were relatively higher than continental shale,the characteristics of hydraulic fracture initiation and propagation were obvious.The injection pressure curve of continental shale is significantly different from that of marine shale due to the fracturing fluid leaking off along bedding interfaces,resulting in nonlinear increase of injection pressure.The characteristics of fracture initiation and main fracture propagation were not obvious,and the acoustic emission energy of continental shale was low.(3)The hydraulic fracture geometry of marine shale is relatively straight,and two main fractures are initiated from spiral perforations.The hydraulic fracture morphology of co
作者
郭鹏
李晓
李守定
郑博
毛天桥
GUO Peng;LI Xiao;LI Shouding;ZHENG Bo;MAO Tianqiao(Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Institute of Energy,School of Earth and Space Sciences,Peking University,Beijing 100871,China)
出处
《工程地质学报》
CSCD
北大核心
2024年第4期1273-1280,共8页
Journal of Engineering Geology
基金
国家自然科学基金项目(资助号:42090023)
国家重点研发计划(资助号:2020YFA0710504)。
关键词
龙马溪海相页岩
长7段陆相页岩
力学特性
水力裂缝形态
压裂液黏度
Longmaxi marine shale
Chang 7 member continental shale
Mechanical properties
Hydraulic fracture geometry
Fluid viscosity
