Absolute permeability of McMurray formation oil sands at low confining stresses

The Athabasca Deposit is the richest of the Alberta bitumen reservoirs with the majority of its recoverable reserves contained in the McMurray Formation. It has been estimated that only about 10% of Athabasca oil sands deposits are surface mineable; thus the vast majority of the bitumen will be recovered by means of in situ extraction technology. A special form of steam flooding, known as steam assisted gravity drainage (SAGD), is being used as the most promising in situ process for the McMurray Formation oil sands.;The SAGD process results in shear stresses and deformations that affect formation absolute permeability. The absolute permeability of the reservoir controls the drainage of fluids from the steam front and therefore the frontal steam advance rate and the bitumen production rate; it is one of the most important parameters in the effectiveness of the SAGD process.;An experimental study of the geomechanical behavior of McMurray Formation oil sand, specifically, the change in absolute permeability during shear at low confining pressures, was the primary objective of this thesis. Both undisturbed and reconstituted specimens were tested in this research program. The undisturbed specimens were obtained by coring a block of bitumen-free oil sand both vertically and horizontally. Since this block of locked sand is bitumen-free, no disturbance to the fabric of the cored specimens was induced by having to extract the bitumen.;Image analysis was employed to study the fabric of the undisturbed oil sand block sample. Structure anisotropy of the sand due to preferred particle orientation was identified.;A new computer controlled stress path triaxial testing system with the capability of continuous measurement of permeability during shear was developed for this study. Test procedures for the preparation of dense reconstituted specimens and for saturation of specimens were developed. A special method was derived for the analysis of permeability tests with lubricated end configuration.;The testing program included stress-strain and permeability tests on both vertical and horizontal undisturbed specimens. Inherent anisotropy was observed in strength, compressibility and permeability. A simple model for the prediction of changes in the absolute permeability is presented.;A methodology is presented in which the laboratory results can be implemented for reservoir numerical modeling of oil sands. A numerical reservoir simulator, FLAC, with strain softening behavior incorporated into the constitutive model, was used for this purpose.