Rich solvent - Steam assisted gravity drainage (RS-SAGD): An option for clean oil sands recovery processes

Abstract

The impact of steam generation on Steam-Assisted Gravity Drainage (SAGD) process economics and environmental impacts have led to various modifications of SAGD including solvent co-injection with steam. One example is the Expanding Solvent Steam-Assisted Gravity Drainage (ES-SAGD) process where 1–5 vol% solvent is injected with the steam into the reservoir. The solvent travels with the steam to the edge of depletion chamber dissolving into the oil thereby mobilizing the oil more than would have been achieved with heating alone. This means lower steam-to-oil ratio and thus, greater thermal efficiency, lower emissions intensity, and water consumption intensity. However, processes where the majority of the fluid injected is steam are still overly emissive and expensive to operate. There is a need to develop carbon-neutral bitumen production processes. Rich Solvent-SAGD (RS-SAGD) aims at injecting mostly solvent into the reservoir with small amounts of steam to achieve radically lower emissions and water consumption intensities than that of SAGD. Here, a RS-SAGD process is investigated where the solvent content is >60 vol% by using detailed thermal-solvent reservoir simulation in an Athabasca oil sands reservoir. The results reveal that RS-SAGD yields higher oil rate than that of SAGD and the process has significantly higher energy efficiency, up to 96% lower emissions and water consumption intensities than that of SAGD. Given the performance of RS-SAGD processes, oil sands operators should consider such processes for future operations.