Three-dimensional visualization of the evolution of pores and fractures in reservoir rocks under triaxial stress

To study the evolution of pores and fractures in reservoir rocks under triaxial stress conditions at the mesoscale, three-dimensional (3D) visualization of coal and shale was performed using computed tomography (CT) scanning and real-time acoustic emission (AE) signal monitoring. The experiment verified that the pores and fractures of the reservoir rocks increased, and the AE signals increased accordingly with the increase in stress. The pore and fracture evolution processes in coal and shale under triaxial stress conditions can be divided into three stages: initial, expansion, and penetration. Compared with coal, the pores and fractures in shale have a shorter penetration stage, indicating that the shale failure process is more rapid. Based on the Rickman formula, modified brittleness index calculation formulas for the tested shale were established. The results of the modified calculations and the CT scan results of pores and fractures can be mutually verified. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The evolution of pores and fractures in reservoir rocks under triaxial stress conditions was studied using CT scanning and real-time AE signal monitoring. The process can be divided into three stages: initial, expansion, and penetration; shale has a shorter penetration stage compared to coal, indicating a more rapid failure process; modified brittleness index calculation formulas for shale were established and verified with CT scan results.