Experimental Studies of Thermally Induced Deformation and Fracture Generation in Clay Shale

ABSTRACT

In thermal enhanced oil recovery process, the clay shale formations above the oil sands reservoirs may be subjected to high pressures up to 10MPa and high temperatures up to 300°C. The responses of the clay shale are very critical for designing or operations of thermal recovery processes. Maintaining wellbore and caprock integrities prevents incidents such as borehole collapse and leakage through caprock. Thermally induced deformation and fracturing in shale impacts on wellbore and caprock integrities. Most previous investigations focused on the mechanical properties of the clay shale. However, limited experimental work has been conducted to investigate the thermal response of clay shale under thermal operation conditions.

In this research, the thermal response of clay shale under different confining pressure conditions is investigated. Laboratory confined and unconfined tests were conducted on Colorado Shale cores which were retrieved from the overburden shale formation above the oil sands reservoirs in Cold Lake area, Alberta, Canada. The shale cores were heated at different heating rates and were subjected to different pressure conditions. The thermally induced deformation and fracturing responses in shale have been captured by X-ray computed tomography scanning (CT scan). The results show that under slow heating rates the shale sample maintains its integrity but display irreversible contraction after cooling to room temperature. Under high heating rates, the samples lose their integrity.

A full version of this paper is available on OnePetro Online.