Evaluation of Pressure and Temperature Sensitivity of Heavy Oil Sands in North Sea through Laboratory Measurement and Rock-Physical Modeling

Abstract

Summary We investigate the elastic properties of heavy oil sands from the North Sea through laboratory measurements and rock-physical modeling. Four samples are measured under changing pressure and temperature conditions, during which the velocity and porosity variations are recorded and analyzed. The pore fluids effect (saturation) is also investigated through comparing the dry and wet sample measurements. Besides, the influence of pressure type (pore pressure vs. confining pressure) is studied by comparing the measurements under the same differential pressure but different confining and pore pressures. Measurement results reveal that pressure and temperature have significant influences on the porosity and velocity of the samples; fluid saturation significantly increases the P-wave velocity while it slightly decreases the S-wave velocity; different pressure types cause evident differences in the P-wave velocities. In the rock-physical modeling, we apply four theoretical models and improve the modeling results by integrating the variations of porosity and pore fluids moduli at different pressures and temperatures. Comparison with measured data justifies that the updated modeling results improve the prediction, and among the four models, cementation theory achieves the best prediction results. This study quantitatively characterizes the pressure- and temperature-dependent elastic properties of North Sea heavy oil sands, which can provide a better understanding of the in-situ properties and also facilitate future exploration and production monitoring of the heavy oil reservoirs.