海陆过渡相不同页岩岩相的岩石力学特性及能量演化特征

针对海陆过渡相不同页岩岩相岩石力学特性及能量演化特征认识不足的问题,以鄂尔多斯盆地东缘二叠系山西组山₂³亚段井下岩样为研究对象,开展了系列实验研究。结果表明:不同页岩岩相的力学特性差异较大,在单轴压缩实验下,硅质页岩相、黏土质页岩相抗压强度平均值分别为58.5、17.9 MPa;在单轴压缩条件下不同页岩岩相均有较强的脆性且为劈裂破坏,随围压增大,塑性增强且转变为剪切破坏,硅质页岩相破坏最严重;不同页岩岩相在峰值强度点处的能量参数有较大差异且受围压的影响程度不同,单轴压缩条件下硅质页岩相、黏土质页岩相、混合质页岩相的平均总能量分别为0.071、0.016、0.044 J/cm³。研究成果对海陆过渡相页岩储层井壁稳定和压裂优化研究具有一定的参考意义。

Rock Mechanical Properties and Energy Evolution Characteristics of Different Shale Lithofacies in Marine-Continental Transition Facies

In view of the insufficient understanding of rock mechanical properties and energy evolution characteristics of different shale lithofacies in the marine-continental transition facies, a series of experimental studies were carried out with the downhole rock samples from the Shan₂³ sub-member of the Permian Shanxi Formation in the eastern margin of the Ordos Basin as the study object. The result shows: The mechanical properties of different shale facies are quite different. Under the uniaxial compression test, the average compressive strengths of the siliceous shale facies and clay shale facies are 58.5 and 17.9 MPa, respectively. Under the condition of uniaxial compression, different shale lithofacies have strong brittleness and split failure, with the increase of confining pressure, the plasticity increases and transforms into shear failure, and the siliceous shale facies is the most severely damaged. The energy parameters of different shale lithofacies at the peak strength point are quite different and are affected by the confining pressure to different degrees. The average total energy of siliceous shale facies, clay shale facies and mixed shale facies under uniaxial compression is 0.071, 0.016 and 0.044 J/cm³, respectively. The research results have certain reference significance for the study of wellbore stability and fracturing optimization of marine-continental transition shale reservoirs.