Rock physics modeling of a bitumen saturated reservoir with unconsolidated sands

Evan Mutual, David Cho, Kristopher A. Innanen

Time-lapse (4D) seismic monitoring of thermal heavy oil production represents a simple and cost-effective method of characterizing the spatial changes in reservoir conditions due to steam injection. Using 4D AVO inversion techniques, we can estimate the changes in elastic properties due to production. To understand these elastic property changes in terms of more meaningful petrophysical parameters, we must consider the rock physics associated with our reservoir. Conventional reservoir targets can typically be modeled with standard sand and shale parameters using Batzle-Wang (1992) or Gassmann (1951) to investigate the fluid effects. In shallow heavy oil reservoirs such as the McMurray formation, the rock physics are more complex and these standard relationships are insufficient. In this study, a 4D rock physics model is created that accounts for both the unconsolidated nature of our reservoir and the finite shear modulus associated with the quasi-solid bitumen. This modeling is essential in interpreting 4D AVO inversion results and can be used as an input to a 4D rock physics inversion.