Reducing the Environmental Impact of Bitumen Extraction with ES-SAGD Process



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Steam Assisted Gravity Drainage (SAGD) is a proven enhanced oil recovery technique for oil sand extraction. However, the environmental and economic challenges associated with excessive greenhouse gas emissions due to the combustion of significant amount of natural gas and consumption of large amount of fresh water for steam generation limit the application of this technology. To address these issues, various SAGD modifications have been developed, among those, SAGD with solvent co-injection is one of the most prospective techniques.

In this experimental study, the effectiveness of base SAGD and Expanding Solvent SAGD (ES-SAGD) was tested on a Peace River bitumen. All experiments were conducted using a two-dimensional cylindrical physical model. In order to investigate the influence of in-situ asphaltene precipitation on the performance of ES-SAGD process, three different types of solvent were considered as hydrocarbon additives; asphaltene soluble (toluene), asphaltene insoluble (n-hexane), and solvent with intermediate solubility parameter (cyclohexane). Different strategies for solvent injection were examined.

In all experiments, temperature profiles at 47 different positions, produces oil and water were monitored continuously. Viscosity and API gravity of original and produced oil samples were measured. This study reveals that co-injection of hydrocarbon solvents with steam enhances the efficiency of SAGD process in terms of oil production, level of oil upgrading, steam to oil ratio and energy consumption. It was also concluded that selection the solvent type and injection strategy are important parameters for the design of hybrid SAGD process.