An analysis of tensile strength, fracture initiation and propagation in anisotropic rock (gas shale) using Brazilian tests equipped with high speed video and acoustic emission

Abstract

This study attempts to further our knowledge of fracture behaviour by establishing an experimental system that links tensile strength, fracture initiation and propagation of an anisotropic rock (Mancos Shale) using an integrated Brazilian Test Setup equipped with Acoustic Emission and High Speed Video. The unique experimental conguration was applied to an anisotropic gas shale (Mancos Shale) in addition to other petroleum related reservoir rocks (such as sandstone and chalk). The variation in tensile strength, fracture initiation location, propagation time and the failure pattern are examined as a function between the layer plane and the loading direction. A time shift was shown to exist between the time at ultimate tensile stress and the time at fracture initiation. This phenomenon has been dubbed the Naet Shift.