A Case Study: Steamflooding to Enhance Recovery of a Waterflooded Light-Oil Reservoir

Abstract Steamflooding in heavy-oil sands is well documented as a mature technology, and while steam has been injected into light-oil low-permeability sands for almost as long, the mechanisms and effectiveness of this process are much less understood because of flow complexities in these sands and complexities of high-pressure steam injection. The full-length paper details the examination of thermal recovery in such a reservoir by use of physical and numerical simulations. Steamflooding can improve upon performance of a waterflooded light-oil reservoir and enhance its oil recovery. The mechanisms such as wettability alteration, interfacial tension, and threshold-pressure-gradient decline contribute to higher oil displacement and sweep efficiency. Vaporization, viscosity reduction, thermal expansion, and relative permeability variation account for more than three-fourths of the incremental recovery in steamflooding. The steamflooded light-oil reservoir in this paper is a low-permeability reservoir with a high wax content and high oil viscosity around 50 mPa.s. It underwent more than 10 years of waterflooding with only 10% of the original oil in place (OOIP) recovered from the reservoir. Challenges faced in this complex project were related to the heterogeneous nature of the reservoir, limited sand continuity, unfavorable mobility for the ongoing waterflooding, associated high threshold-pressure gradient, and poor injection response. The steamflooding was carried out to enhance oil recovery after waterflooding. The paper discusses the mechanisms, strategies, barriers, and difficulties of reaching high recovery for steamflooding in a waterflooded light-oil low-permeability reservoir. A detailed reservoir-engineering study focused on the development method, the injection and production system, and the physical and numerical simulation.