Numerical analysis of oil sand under nonisothermal conditions

Abstract

Theoretical expressions, in terms of elastic and thermal properties of multiphase soil systems, have been derived for the change in pore fluid pressure under undrained conditions and the change in soil stress under drained conditions. A methodology is proposed for linking these equations to Biot's generalized coupled flow and deformation formulations in a form suitable for finite-element implementation. The thermoconsolidation numerical model developed for this study employs a modified form of the hyperbolic stress-strain relationship that can account for the shear-induced volume change (dilation) effects. The numerical model is verified under drained conditions and then applied to simulate three triaxial experiments that previously had been performed on good-quality Athabasca oil sand samples. The analyzed tests include drained compression at room temperature, drained compression at an elevated temperature, and an undrained heating under anisotropic stress conditions. The numerical simulations were in remarkable agreement with the observed response under drained and undrained conditions, and the results indicated that the dilative effectsplây a crucial rolein satisfactorily modelling the response of oil sands, particularly under undrained conditions. The application of the numerical model in analyzing the laboratory tests provides a means for determining some of the soil parameters that would otherwise be difficult to measure. Key words: finite elements, numerical modelling, undrained heating, drained heating, thermal consolidation, oil sand, stiffness properties, thermal properties.