Crack Propagation Characteristics of Hard Shale Based on Acoustic Emission

doi:10.3969/j.issn.1006-6535.2024.06.017

Abstract

Abstract: To address the issue of wellbore instability and collapse in shale gas development,with Longmaxi shale as the research subject,based on uniaxial compression experiments and acoustic emission technology,the influences of bedding dip angles on shale failure,crack types,and the variation process of characteristic parameters of acoustic emission during the compression process were investigated.The results indicate that the main crack of the rock sample inclined at an angle of 30° traverses the bedding plane.The failure of the rock is predominantly governed by the rock matrix,and a certain bedding weak plane exists,resulting in the inclined macrocrack not fully propagating along the bedding plane.The coupling failure of rock samples with dip angles of 45° and 60° occurs.The rock failure is mainly controlled by the bedding plane,resulting in conspicuous slip failure.The failure plane along the bedding weak plane penetrates the entire rock sample.The rock sample with a dip angle of 90° is dominated by splitting failure.The crack propagation is influenced by the bedding plane,and the rock failure is governed by the weak bedding plane and the rock matrix.The count of acoustic emission ringing exhibits a fluctuating pattern and a disparity exists.Prior to the peak stress and when the rock sample is on the verge of being destroyed,the count of ringing increases rapidly to the maximum value.For the majority of the time,the acoustic emission energy is relatively low,and the acoustic emission energy rises as the crack propagates.When the rock sample fractures,the release of acoustic emission energy attains the maximum value.The positioning point display model processed by the clustering algorithm is superior to the Geiger algorithm positioning model in the expression of single concentrated rock macro-surface cracks and shedding areas.This study can provide a theoretical reference for wellbore stability analysis in shale gas development.

Key words: uniaxial compression, acoustic emission, friable hard shale, three-dimensional positioning, fracture evolution

CLC Number:

TE38

Zhang Zhen, Cui Shuai, Liu Huize, Liu Houbin, Wu Pengcheng, Gou Qiyong. Crack Propagation Characteristics of Hard Shale Based on Acoustic Emission[J]. Special Oil & Gas Reservoirs, 2024, 31(6): 137-144.

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