基于数字图像处理的非均质岩石材料细观尺度应力分析

Stress analysis of heterogeneous rock material at mesoscopic scale based on digital image processing technology

以冀中坳陷碳酸盐岩储层为例,利用碳酸盐岩微观结构的图像信息,确定地应力数值模拟计算网格的合适尺寸,将数字图像处理技术引入非均质碳酸盐岩岩石材料细观尺度的应力分布计算中,将表征岩石细观结构特征的量与岩石物理力学参数等宏观的量有机结合,精确预测碳酸盐岩非均质储层裂缝发育及分布的区域。结果表明:研究区域最大水平主应力为-59.51^-95.09 MPa,最小水平主应力为-34.05^-52.58 MPa;Mises等效应力为56.84~83.15 MPa;研究区域最大总应变为2.097×10-4,最小总应变为1.392×10-4;岩心样品在左上区域和右下区域均出现应力集中和变形不协调的情况,预测为裂缝主要扩展和分布的区域;基于数字图像处理技术能够更真实、有效地表征储层岩石的非均质性。

Taking the carbonate reservoir of Jizhong depression as an example in this paper, the image information of carbon-ate rock microscopic structure was used to determine the appropriate grid size for the numerical simulation of ground stress field. The digital image processing technology was introduced into the distribution calculation of meso-scale stress of hetero-geneous carbonate rock material. Combining those quantities characterizing the microscopic structure feature of rock with the physical and mechanical parameters of rock and other macroscopic quantities, the fracture developing and distributing area in carbonate heterogeneous reservoirs can be predicted accurately. The results show that the maximum horizontal principal stress range is -59. 51--95. 09 MPa, and the minimum horizontal principal stress is -34. 05--52. 58 MPa. Mises equivalent stress is 56. 84-83. 15 MPa. The maximum total strain of the studied area is 2. 097×10^-4, and the minimum total strain is1. 392×10^-4. The stress concentration and incompatible deformation occur in the up-left and the down-right regions of the core samples, which is predicted to be the main developing and distributing area of the fractures. The numerical calculation model based on digital image processing technology can reflect the real microscopic structure of reservoir rock material, and characterize the heterogeneity of reservoir rock more reliably and effectively.