Abstract
In the Athabasca oil sands, which is a large deposit of heavy oil, located in northeast Alberta, Canada, it is common that impermeable shale intricately exists within the reservoirs and can potentially act as permeability baffles. For reservoir management, it is important to precisely delineate the intrareservoir shale. The main goals of this study are to establish a rock physics model of poorly consolidated, heavy oil-saturated sands and to estimate density by applying three-term AVO inversion to P-P reflected and P-S converted wave data.
We first explore viscoelastic features of heavy oil by using ultrasonic velocity measurement data collected over a wide temperature range. By using viscoelastic model, temperature and frequency dependences of the bulk and shear moduli are predicted. Furthermore, we establish a rock physics model of poorly-consolidated, heavy-oil saturated sands. For the case of inclusions in a matrix, Generalized Singular Approximation method is used to obtain the effective properties. The model incorporates the viscoelastic features of heavy oil to estimate velocity dispersion associated with the viscosities.
Density has a large contrast between reservoir and shale and is a desired property for reservoir delineation in the Athabasca oil sands. A P-P and P-S joint AVO inversion method is developed by extending an Bayesian inversion technique to multicomponent data. We apply the developed method to the Hangingstone oilfield to estimate density volume. The estimated density is practically consistent with the well log, implying that the method can provide a quantitative description of oil sands reservoir.
