Abstract
This paper presents laboratory investigations on the vertically drilled borehole specimens belonging to the Barren Measure Formation shales in the Raniganj sub-basin, India. These shales were examined for their mineralogical makeup and geomechanical properties through a series of laboratory experiments viz. X-ray diffraction, uniaxial tests, single-stage triaxial tests, tensile strength tests, porosity, and permeability measurements. The mineralogical assessment has revealed dominant clay minerals and moderate silica content. The mechanical tests yielded a high Young’s modulus and low Poisson’s ratio in these shales with brittle to semi-brittle type of failure. The compositional, elastic and tensile brittleness of these shales indicate values that are in good agreement with the brittle nature of gas shales. Furthermore, these shales report low porosity and ultra-low permeability. The Barren Measure Formation in the Raniganj sub-basin is organically rich and was targeted during India’s first exploratory well, yielding natural gas. However, these shales are still in their infancy in terms of their geomechanical attributes. This study also attempted to generate basic data on properties like compressibility, elastic moduli, and tensile strength, which are among the critical parameters controlling the reservoir simulation program. The results of brittleness and failure parameters (elastic moduli, internal friction angle, cohesion, compressive strength and tensile strength) of Barren Measure Formation in Raniganj sub-basin of Damodar Basin, India show high similarity with those of Roseneath Formation in Cooper Basin, Australia revealing their analogous origin.
