Comparison among brittleness, hardness and mineral composition of the Besa River Formation in the Liard Basin, Canada

Rock brittleness is regarded as one of the most crucial geomechanical properties affecting hydraulic fracturing in shale reservoirs. Numerous studies have been conducted to quantify rock brittleness, most of which were based on mineralogical and geomechanical properties. This study aims to clarify relationship between brittleness indices and multi-proxies of the Devonian Besa River Formation, which is a frontier shale gas play in Western Canada Sedimentary Basin and to suggest an ideal model for mineralogy-based brittleness index. To this end, we calculated Young's modulus and Poisson's ratio from well logs and measured the Leeb hardness from slabbed core surfaces. We also conducted geochemical and sedimentological analyses for the Besa River Formation. Hardness and brittleness are positively correlated with quartz content but negatively with clay mineral content in the formation, whereas carbonate mineral and total organic carbon (TOC) contents show no relationship with hardness and brittleness. Hardness measurements are also well correlated with rock brittleness from well logs and can be a good proxy for the brittleness of Besa River Formation. This study suggests an ideal model for a mineralogy-based brittleness index, considering the influence of biogenic and detrital quartz in the Formation. This model shows a high correlation coefficient with rock brittleness and can be useful to determine the brittleness of rocks with similar characteristics to Besa River Formation.