LABORATORY TESTS FOR MECHANICAL PROPERTIES OF DEEP-SEATED SHALE IN JIAOSHIBA BLOCK OF SICHUAN BASIN

Uniaxial compression experiments on shale specimens of Wufeng-Longmaxi region are carried out to study the mechanical properties within bedding planes under different depths. The deformation feature, compressive strength and five fundamental failure modes are summarized. The result shows that the mechanical parameters of shale within bedding planes under different depths are turned out to be significant difference. Shale blocks within bedding planes present obvious brittle failure characteristics, which mainly forms of splitting failure accompanied by partial or localized shear failure. On the whole, as the sampling angle β enlarges, the elastic modulus and Poisson's ratio increase at first and then decrease. Comparative analyses are carried out for the mechanical parameters varieties of the transverse and longitudinal diversity. The diversity factor of compressive strength is quite larger than that of elastic modulus and Poisson's ratio. The effect of shale bedding planes is one of the main factor for the diversity of strength and failure mode. Bedding plane can determine shale compressive strength and failure mode to some extent. The research provides references for the wellbore stability analysis and hydraulic fracturing design in the shale gas exploitation.