基于数字岩心模型重构的岩石力学行为评价新方法  

A new rock mechanical behavior evaluation method reconstructed based on the digital core model

作　　者：郭建华 佘朝毅[2] 夏连彬 余文帅 苏强 李亚天 GUO Jianhua;SHE Chaoyi;XIA Lianbin;YU Wenshuai;SU Qiang;LI Yatian(Engineering Technology Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610017,China;PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China)

机构地区：[1]中国石油西南油气田公司工程技术研究院 [2]中国石油西南油气田公司

出　　处：《天然气工业》2024年第7期132-143,共12页Natural Gas Industry

基　　金：中国石油天然气股份有限公司重大科技专项“致密砂岩气藏提高采收率关键技术研究”(编号:2023ZZ25);中国石油西南油气田公司重大科技专项“四川盆地中西部地区致密气钻采关键技术研究”(编号:2022ZD01-03)。

摘　　要：石油天然气钻井过程中,上覆非目的地层钻取的岩心数量有限,在一定程度上限制了其岩石力学行为的研究,不利于安全高效钻进。为此,采用数字岩心模型对上覆长井段非目的地层岩石力学行为开展了反演研究,并以四川盆地天府气田上三叠统须家河组地层为例,基于目标层位岩屑组分测试结果与Voronoi理论,建立了用于表征须家河组岩心力学行为的数字岩心三维Voronoi体模型,还原了矿物成分、黏土以及孔隙的空间分布,最后从微观角度分析和研究了岩石的力学特性及损伤演化过程。研究结果表明:①数字岩心单轴压缩变形存在空隙压密、弹性变形、塑性变形和破坏后4个阶段,破坏形式主要为剪切破坏,这与实验结果高度吻合;②在轴向压力加载时,矿物颗粒受到挤压产生应变,当应变超过矿物本身的屈服应变时,矿物开始损伤,并将无法承受的压力传递给邻近矿物颗粒,逐渐形成裂纹和破裂面;③矿物空间分布仅对数字岩心的损伤演化和裂纹发展有影响,颗粒尺寸对弹、塑性以及破坏后阶段的力学行为均有影响;④随着围压增加,抗压强度和残余强度明显增大,且岩心尺寸越大弹性模量和峰值强度越低。结论认为,该方法分析结果与实验结果吻合,为岩心缺少条件下研究钻井过程中上覆地层岩石力学特性提供了新思路,并对破岩机理认识及优化钻头选型与设计具有重要工程意义。In the process of oil and gas well drilling,the cores drilled from the overlying non-target strata is limited in quantity,which,to some extent,limits the researches on rock mechanical behaviors and is not beneficial for safe and efficient drilling.To this end,this paper applies the digital core model to conduct inversion research on the rock mechanical behaviors of the overlying non-target strata in the long hole section.Then,with the Xujiahe Formation of Upper Triassic in the Tianfu Gas Field of the Sichuan Basin as an example,the three-dimensional Voronoi body model of digital core for characterizing the mechanical behaviors of the Xujiahe Formation cores is established on the basis of the cuttings component test results of the target layer and the Voronoi theory.In addition,the spatial distribution of mineral compositions,clay and pores are restored.Finally,the mechanical properties and damage evolution of the rocks are analyzed from a microscopic perspective.And the following research results are obtained.First,the uniaxial compression deformation of digital core is divided into four stages,i.e.,pore compaction,elastic deformation,plastic deformation and post failure,with shear failure as the main failure form,which is highly consistent with the experimental result.Second,under the action of axial pressure,mineral particles are compressed to generate strain.When the strain exceeds the yield strain of the mineral itself,mineral damage begins,and the pressure beyond the bearing capacity is transferred to the neighboring mineral particles to form crack and fracture surface gradually.Third,the spatial distribution of minerals only influences the damage evolution and crack propagation of digital core,and particle size affects the mechanical behaviors in elastic,plastic and post failure stages.Fourth,with the increase of the confining pressure,compression strength and residual strength increase significantly.In addition,the larger the core size,the lower the elastic modulus and peak strength.In conclusion,the analy

关 键 词：数字岩心 力学行为 单轴抗压强度 三维Voronoi 损伤演化 矿物组分 尺寸效应 

分 类 号：TE142[石油与天然气工程—油气勘探] TD315[矿业工程—矿井建设]