VOLUME AND PERMEABILITY CHANGES ASSOCIATED WITH STEAM STIMULATION IN AN OIL SANDS RESERVOIR

Field performance and previous research have indicated that the stress es and deformations caused by steam stimulation processes in oil sands formations alter the oil sands structure. The resulting pore volume c hanges (that is, pore volume and pore interconnectivity) affect the re servoir permeability and water mobility. The relevant geomechanical an d fluid flow properties can be measured in the laboratory under the ap propriate temperature, stress and fluid pressure conditions which simu late field conditions. Reservoir models which incorporate the geomecha nical effects accompanying steam stimulation in oil sands formations c an then incorporate these measured properties. The volume and permeabi lity changes are the results of three effects: a change in the mean pr incipal effective stress, a change in the shear stress and a change in temperature. Testing equipment and experimental procedures to measure these material characteristics are described. Initial test results on Cold Lake oil sands are compared to research published in the literat ure on unconsolidated sands and on sandstones. The stress and material properties which affect such permeability changes are discussed.