In-Situ Reflex (ISR) is a novel solvent-based process that utilizes resistive electric heaters to vaporize solvent and recycle mobilized water downhole. ISR promises a significant reduction in greenhouse gases emissions through the elimination of steam generation and water handling facilities at the surface as well as effectively vaporizes the injected fluid along a wellbore. However, the economic viability of this process is highly dependent on the in-situ refluxing of the solvent which requires an in-depth understanding of the process and associated challenges numerically and analytically. In modeling the SAGD process, optimal operating conditions rely on a relatively constant temperature profile across the major portion of a steam chamber that leads to an excessive energy input requirement. However, ISR optimal operating conditions tend to exhibit different temperature profiles as a result of changing thermal recovery to a solvent diluting mechanism. As such, employing a SAGD analytical model results in misunderstanding the ISR fundamental thermodynamics and hindering further optimization of the process.

This paper is the first time that an unsteady-state semi-analytical model has been developed for predicting ISR performance and shared publicly. The developed model has been validated using numerical simulation data and is capable of properly predicting a temperature distribution in a steam-solvent gaseous chamber in the presence of a fixed source of heat in an injector. This model includes fixed heat sources in both injectors and producers to represent the resistive heater concept, capture the reflux concept, and evaluate the contribution of refluxed solvent to reducing the solvent usage. In addition, the model helps better understand the phase behavior and the effectiveness of various solvents in further analyzing and determining the optimum downhole operating conditions and improving the overall ISR performance and its economic viability.

The proposed model brings an insight into analytical modeling of the ISR process with the aim of increasing an understanding of the heat transfer mechanism, along with identifying the advantages and limitations of using the bottom-hole resistive heater technology. This will lead to a higher predictability of successful field implementation, lower upfront capital cost, higher energy efficiency, and environmentally sustainable development.

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