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Obtaining Geomechanical Information From Hyperspectral Imaging of a Shale Core, Horn River Basin, Western Canada

Abstract

Clay and biogenic silica content have been shown to control the brittleness of Devonian shale formations in western Canada and elsewhere. Increased clay content enhances ductility, whereas biogenic silica enhances brittleness. Carbonate minerals and organic carbon exert less substantial controls on geomechanical properties. Brittleness can be assessed from mineralogical or geochemical analysis of cores or from well logs, but these approaches suffer from relatively low resolution. Scratch tests or impact tests can provide higher resolution assessments, but these approaches cannot connect geomechanical behavior to underlying compositional controls. In this study, we apply hyperspectral imaging to assess the composition of a long shale core from the Horn River Group, Horn River Basin in northeastern British Columbia. This technology has been demonstrated to provide high resolution (< 1 mm) maps of variation in clay, carbonate, quartz and organic carbon content, revealing details and insights into depositional processes not apparent in standard core logging. The compositional maps are compared to geomechanical assessments based on (1) rock composition from electron capture spectroscopy logs, (2) impact tests, and (3) dynamic Young’s modulus and Poisson’s ratio from dipole sonic and density logs. Comparison of the hyperspectral compositional maps to geomechanical results shows a high degree of fidelity between maps of clay content and brittleness: high clay content associated with less brittle behavior and vice versa. We also test whether hyperspectral imaging can distinguish detrital quartz from biogenic-derived quartz, which would enhance brittleness predictions. Our analysis shows that interpretations of a shale formations can be greatly enhanced by hyperspectral imaging, enabling the interpreter to readily connect geomechanical behavior to underlying shale composition and to understand the scale at which geomechanical properties vary, critical information for predicting responses to hydraulic fracturing.