Effect of temperature on ultrasonic velocities of unconsolidated sandstones reservoirs during the SAGD recovery process
Résumé
The steam assisted gravity drainage (SAGD) has been successfully used to enhance the recovery of heavy oil in Western Canada and Eastern Venezuela basins. Pressure and temperature variations during SAGD operations induce complex changes in the elastic properties of the reservoir rock. To study these changes, measurements of ultrasonic wave velocities were performed on both reconstituted samples and natural oil sands samples. Reconstituted samples were made of Fontainebleau sand with a slight cementation formed by a silicate solution. They have a high porosity (about 37 % to 40 %) and a high permeability (about 10-12 m²). Natural oil sands samples are unconsolidated sandstones extracted from the fluvio-estuarine McMurray Formation in Alberta (Canada). The saturating fluids were heavy oil and glycerol with a strongly temperature dependent viscosity. Tests were carried out at different temperatures (in the range -30°C and 80°C) and at different effective pressures (from 1.2 MPa up to 8 MPa). Experimental results showed that the elastic wave velocities measured are strongly dependent on temperature (mainly through the viscosity) whereas little effect of effective pressure was observed. Velocities decrease with increasing temperature and increase with increasing effective pressure. These effects are mainly due to the variations of the saturating fluids properties. The experimental results were afterwards compared with the Ciz and Shapiro [1] approach, a extension of the poroelastic theory of Biot-Gassmann [2, 3], applied for rock filled with the hightly viscous fluids.