X射线衍射残余应力测试技术在纤维状方解石脉体现今应力状态分析中的应用

以济阳坳陷沙三下—沙四上亚段富有机质页岩中发育的纤维状方解石脉体为研究对象,采用X射线衍射残余应力测试技术定量获得方解石脉体受到的现今应力类型及大小,建立方解石脉体剪切破裂的应力模型和判别式,明确方解石脉体中破裂线的力学成因,并分析孔隙流体压力对方解石脉体发育的影响。结果表明纤维状方解石脉体的垂向有效应力为59 MPa,水平有效应力为16 MPa,处于三向挤压的空间应力状态中;任意剖面上的有效应力模型和剪切破裂判别式决定了方解石脉体表现为共轭剪切破裂,破裂线呈折线状或曲线状,理论破裂角为45°或28°,与薄片实际测量结果一致但也受薄片磨制方向影响;孔隙流体压力导致正应力减小而剪应力不变,影响页岩岩石骨架或方解石脉体的破裂方式。

Application of X-ray diffraction residual stress testing technology in the analysis of present stress state of fibrous calcite vein

Taking the fibrous calcite vein developed in the organic-rich shale from the lower Es3 to upper Es4 of Jiyang Depression as the research object,this paper quantitatively obtains the present stress type and size of the fibrous calcite by an X-ray diffraction residual stress testing technology,and establishes the stress model of the shear fracture of the calcite vein.The mechanical origin of fracture line in the calcite vein is determined and the influence of pore fluid pressure on the development of the calcite vein is analyzed.The results show that the vertical effective stress of the fibrous calcite vein is 59 MPa,the horizontal effective stress is 16 MPa,and the fibrous calcite vein is in the state of three-dimensional compression space stress.The effective stress model and the shear fracture discriminant on arbitrary section determine that the calcite vein appears as conjugate shear fracture.The fracture is a polyline or curved,and the theoretical fracture angle is 45°or 28°,which are consistent with the actual measurements from thin sections,but could also be affected by the polished direction of the thin section.The pore fluid pressure causes the normal stress to decrease while the shear stress remains unchanged,which affects the fracture mode of the shale rock skeleton or the calcite vein.