Steam Additives to Reduce the Steam-Oil Ratio in SAGD: Experimental Analysis, Pilot Design, and Field Application

Abstract

Producing bitumen using SAGD requires a significant amount of water and energy, resulting in a large amount of greenhouse gas emissions. Therefore, reducing the steam-oil ratio (SOR) in SAGD is critical to make the oil recovery process profitable and sustainable in a carbon-constrained world. This paper presents the potential benefits of co-injecting water-soluble volatile additives with steam in SAGD. The objective of the process is to decrease the SOR while maintaining SAGD-like oil production rates at economical chemical additives concentrations. Through a comprehensive experimental study, multiphase behaviour of the additive-water-bitumen system, mixture's viscosity, additive thermal stability, adsorption, emulsion stability, and recovery performance were evaluated. Extensive coreflooding experimental tests quantified the potential for improved oil recovery and SOR reduction. The experimental variables included additive concentration, water-oil ratio, and temperature. The studies showed that the additives improved oil recovery by promoting the formation of oil-in-water emulsions at the producing SOR. A series of reservoir simulation studies were also conducted for a field pilot design and evaluation of key performance indicators. Two different methodologies, equilibrium and non-equilibrium, were used to model the steam additive behaviour under both transient and steady-state conditions. Data obtained from coreflooding and viscosity measurements were the primary inputs of the reservoir simulation models. The fine-tuned reservoir simulation model quantified the technology uncertainties using multiple equally probable realizations of the reservoir to design and optimize the field pilot's injection scenarios and operating conditions. The simulation results showed SOR reduction of up to 25% with steam additives co-injection for the designed concentrations. Different phenomena such as additive transportation, condensation, additive degradation, and adsorption in a growing steam chamber were included in the numerical model. Based on the experimental and reservoir simulation results, a 4-well pair field pilot was designed, built, and put in operation at the Surmont SAGD project.