基于Smooth-Joint模型的层状页岩力学特性研究

普光气田陆相页岩气资源潜力巨大，侏罗系千佛崖组一段页岩气大面积分布，埋深适中，页岩气资源量为4 239.5亿m³。为实现页岩气的高效开发，在室内页岩单轴压缩力学试验的基础上，利用颗粒离散元法建立页岩的单轴压缩模型和Smooth-Joint节理模型，探讨宏观各向同性页岩单轴压缩破坏、变形及强度特征，以及不同Smooth-Joint节理倾角对岩石力学特性的影响。数值试验与室内试验分析结果表明，节理面的存在降低了岩石的抗压强度；岩体的抗压强度随着节理倾角的改变而改变，随着节理倾角的增大，岩体的强度先降低随后增大；当节理面与潜在破坏面的方向相近时，即节理面倾角θ=45°+φ_s/2时，岩体受压破坏沿节理面发生，岩体强度下降得最多；层状页岩单轴压缩全应力—应变曲线可以分为5个阶段，阶段Ⅰ岩样内部裂纹闭合体积减小、阶段Ⅱ弹性变形过程(总体积应变增量等于弹性体积应变增量)、阶段Ⅲ裂纹稳定扩展(弹性变形)、阶段Ⅳ裂缝非稳定扩展(塑性变形阶段)、阶段Ⅴ试件裂缝继续扩展延伸直至达到峰后强度σ_p停止。该研究结果为普光陆相千佛崖组页岩气的开发提供...

Study on mechanical properties of layered shale based on Smooth-Joint model

The potential of continental shale gas resources in Puguang Gas Field is huge.The shale gas in the first member of the Jurassic Qianfoya Formation is widely distributed with moderate burial depth，and the shale gas resource is 423.95 billion m³.In order to realize the efficient development of shale gas，based on the indoor uniaxial compression mechanical test of shale，the uniaxial compression model and Smooth-Joint joint model of shale are established by using the particle discrete element method in this paper.The failure，deformation and strength characteristics of macroscopic isotropic shale under uniaxial compression，and the influence of different Smooth-Joint joint dip angles on the mechanical properties of rock are discussed.The results of numerical test and laboratory test show that the existence of joint surface reduces the compressive strength of rock.The compressive strength of rock mass changes with the change of joint dip angle.With the increase of joint dip angle，the strength of rock mass decreases first and then increases.When the direction of joint surface is close to that of potential failure surface，that is，when the dip angle of joint surface is θ=45°+φ_s/2，the compressive failure of rock mass occurs along the joint surface，and the strength of rock mass decreases most.The full stress-strain curve of layered shale under uniaxial compression can be divided into five stages.The closed volume of internal cracks in stage Ⅰ decreases，the elastic deformation process in stage Ⅱ（the total volume strain increment is equal to the elastic volume strain increment），the stable crack propagation in stage Ⅲ（elastic deformation），the unstable crack propagation in stage Ⅳ（plastic deformation stage），and the crack extension of stage Ⅴ specimen continues until the peak strength σ_p stops.The research results provide a certain reference for the development of shale gas in Puguang Continental Qianfoya Formation.Taking Well Ye 1 of Puguang Gas Field as an example，the well was successfully fractured，the gas production after fracturing was high，and the application effect of reservoir transformation was good.