Numerical Investigation of Potential Injection Strategies To Reduce Shale Barrier Impacts on SAGD Process

Abstract

Summary It is well known that shale barriers significantly reduce steam-assisted gravity drainage (SAGD) performance in Athabasca fields. An extensive 2D simulation study shows that the flow resistance at the end of shale barriers and the extra heat absorbed by the residual water inside the unproductive shale barrier are the main reasons for the shale barrier effects. Long continuous shale barriers located vertically above or near the wellbore delay production performance significantly. We investigated potential strategies, including solvent coinjection, top injector application, or a combination of both, to reduce the shale barrier impacts. Solvent in the vapour phase can pass through the narrow flow path at the end of a shale barrier. Meanwhile, because the phase condenses from vapour to liquid, solvent efficiently reduces the flow resistance of the shale barrier. Liquid solvent coinjection can accelerate the near-wellbore flow and reduce the residual oil saturation at the wellbore vicinity. Coinjecting a multicomponent solvent can flush out the oil at different areas with different drainage mechanisms from vaporized and liquid components. Additional injector application at the top of the reservoir results in only marginal improvement.