A Geomechanical Mechanism that Counteracts Flow Channeling Induced by Reservoir Thermal Drawdown

Abstract

This study employs a coupled thermal–hydrologic–mechanical (THM) model to investigate flow channeling associated with reservoir thermal drawdown. Flow channeling refers to the phenomenon that the fractures carrying more flow tend to cool faster and may subsequently dilate more than fractures carrying less flow, thereby causing increasingly severe flow concentration into the a small number of fractures. Our study discovers that the anisotropic thermal stress in a cooling reservoir tends to loosen fractures that are normal to the primary flow direction more than do fractures along the primary flow direction. This mechanism can counteract the flow channeling potential by promoting a diffuser flow pattern. We also found that the significance of the effects of this mechanism dependent on certain inherent characteristics of the fracture network. Fracture network patterns that are prone to and those with strong inherent resistance to flow channeling need to be identified.