Temperature-Dependent Deformation Prediction of Oil Sand by Coupled Geomechanical and Fluid Flow Modeling

Kashihara, Koji (JAPEX) | Rutqvist, Jonny (Lawrence Berkeley National Laboratory)



Reservoir deformation during steam injection of SAGD operation can result in the increase in formation permeability that can positively impact to the bitumen production. The reservoir deformation behavior is controlled by the mechanical properties of oil sand, which are highly dependent on temperature. This work is focused on the temperature dependency of elastic properties of oil sand and its impact on geomechanical responses during a SAGD operation. Coupled geomechanical and fluid flow modeling technique is employed to illuminate the impact of the change in elastic properties to the reservoir deformation behavior.

Rock physics modeling is conducted at first for quantifying the temperature effect on the elastic properties of oil sand. Based on the investigation of log data from an actual SAGD operation field, we used the soft-sand model to calculate dry-frame elastic properties of the unconsolidated sand. We then applied and investigated several substitution methods to quantify the effect of the pore-filling bitumen on the elastic properties of the oil sand. We selected one of the solid substitution methods instead of Gassmann equation because bitumen behaves like solid at low temperature. The coupled hydraulic, thermal, and geomechanical simulator, TOUGH-FLAC, is used to investigate the effect of oil sand's elasticity on reservoir deformation behavior. The coupled modeling for SAGD is conducted for two simple cases; one case with the elastic properties at original reservoir temperature and the other case with the updated elastic properties considering the increased temperature. Comparison of the results from the two cases demonstrates the importance of considering the effect of temperature on the elastic properties of oil sand. This work is new in terms of combining rock physics modeling for quantitative description of the oil sand elastic properties and the coupled hydraulic, thermal, and geomechanical modeling considering the temperature-dependent elastic properties of oil sand.