Multicomponent Solvent Co-injection with Steam in Heavy and Extra-Heavy Oil Reservoirs

Expanding solvent steam assisted gravity drainage (ES-SAGD) is a hybrid steam–solvent oil recovery process that can be used to extract oil from heavy oil and bitumen reservoirs. It is a variation of the SAGD process in which only steam is used. In ES-SAGD, the mobilization of highly viscous oil is enhanced through a combination of heat and mass transfer processes, which results in significantly reduced volumes of water and natural gas needed to generate the injected steam, making ES-SAGD more energy efficient and environmentally sustainable relative to SAGD. Both SAGD and ES-SAGD use the same well configuration, and solvent co-injection in existing SAGD projects often requires limited facility modifications. This study investigates different aspects of ES-SAGD experimentally, based on typical Long Lake reservoir properties and operating conditions, using different concentrations of gas condensate. Furthermore, this study provides phase behavior insights to govern the selection of appropriate solvents for use in ES-SAGD. The performance of the gas condensate ES-SAGD cases in this study exceeded that of the baseline SAGD case in terms of oil production rates, energy efficiency, and postproduction water handling. These findings were instrumental in the design and implementation of a field pilot project by Nexen Energy ULC in the Athabasca Oil Sands that began in September 2014.