Experimental and constitutive study of the thermo-mechanical behavior of an oil sand

摘要

The understanding of the thermo-mechanical behavior of oil sand deposits is of prime importancernin the safe and economic design of thermal oil recovery processes in Alberta, Canada. The present study focusesrnon both the experimental and constitutive characterizations of the thermo-mechanical behavior of “Firebag”rnoil sand from the Athabasca area in Alberta, Canada. Isothermal triaxial compression tests at different levelsrnof confining pressure and temperature were performed on samples obtained from a depth of approximatelyrn270 m. Experimental results at ambient temperature show a quite brittle behavior with relatively large peak andrnresidual strengths due to the initially dense and interlocked structure of the granular material. High temperaturesrnwere found to strongly increase the ductility and decrease the stiffness and strength of the samples. Based onrnthe experimental results, a simple non-associated plasticity model is proposed to realistically describe the nonisothermalrnmechanical behavior of Firebag oil sands. The proposed model is built on the Mohr-Coulomb plasticrnlimit enriched with constitutive features that enable it to capture important behavioral aspects of oil sands suchrnas high peak strength and dilatancy. The adequacy of the model is verified through the simulation of laboratoryrntriaxial test results at different temperatures. The model provides a consistent and yet simple framework for easyrnimplementation into a coupled reservoir-geomechanics computer algorithm for thermal oil recovery processes.