The steam stimulation process is a proven, commercially viable recovery process in oil sand reservoirs. However, uncertainties remain in the analysis of the recovery mechanism of the process. One of the important aspects is the nature of shear failure created by pore pressure increase in the reservoir during steam injection. The changes in mass and heat transport properties in the heterogeneously deformed failure zone have been shown to be major factors affecting the recovery mechanism. This paper describes the theoretical and practical aspects of representing the shear failure sone in reservoir simulation, by means of pseudo relative permeability functions.

Relative permeability hysteresis is commonly used in the simulation of the steam stimulation process. The paper gives the theory for the pseudo relative permeabilities caused by heterogeneously failed media. The new functions are derived by considering the shear failure phenomenon and have a characteristic similar to relative permeability hysteresis. A set of stress-dependent pseudo relative permeabilities is proposed and a practical method for the use of the pseudo functions (including hysteresis) in a reservoir simulator is given. The pseudo relative permeability model is applied in the simulation of a well in the Esso Cold Lake site and shows that the hysteresis should be stress-dependent rather than saturation-dependent.

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