Creating Tensile Fractures in Colorado Shale Using an Unconfined Fast Heating Test

Under a high heating rate, thermally induced pore pressure is readily developed in low-permeability soft mudrocks, such as clay shale. Thermally induced pore pressure may lead to tensile fracturing in soft mudrocks and pose severe issues for thermal projects that include thermal heavy oil recovery and radioactive waste disposal. This article presents experimental investigations on the possibility of creating tensile fractures in a clay shale (Colorado shale) sample using a fast heating test. An unconfined fast heating test was conducted on a Colorado shale sample, which was retrieved from an overburdened shale formation above oil sand reservoirs in the Cold Lake area in Alberta, Canada. X-ray computed tomography scanning was applied to observe the thermally induced tensile fracturing behavior. A fully coupled thermal-hydromechanical finite element analysis was performed to examine the thermally induced pore pressure development in the sample. Experimental work indicates that Colorado shale loses its integrity when the sample’s pore pressure is higher than its tensile strength. The generated fractures in Colorado shale are almost parallel to shale’s intrinsic bedding plane.