STARS
Thermal & Advanced
Processes Simulator

A Methodological Analysis of the Mechanisms Associated to Steam-Solvent Co-injection Processes using Dynamic-Gridding

Hybrid steam-solvent processes are gained importance as a thermal recovery process for heavy oils in recent years. A number of pilot projects during the last decade indicates the increasing interest in this technology. Steam-solvent co-injection process aims to accelerate oil production, increment ultimate oil recovery, reduce energy and water disposal requirements and the volume of emitted greenhouse gases compared to Steam-Assisted Gravity Drainage (SAGD) process. Among the identified physical mechanisms that play a role during the hybrid steam-solvent processes are the heat transfer phenomena, the gravity drainage and viscous flow, the solvent mass transfer and, in particular, the mass diffusion/dispersion phenomena. The major consequence of this complex interplay is the improvement of oil phase mobility which is controlled by the reduction in oil phase viscosity at the edge of the steam chamber. It follows that a detailed representation of this narrow zone is necessary to capture the dominating physical phenomena involved.

In this work, we present numerical results of the Expanding-Solvent Steam-Assisted Gravity Drainage (ES-SAGD) process using an adaptive dynamic gridding in the CMG commercial simulator. Comparisons are performed between SAGD and ES-SAGD after characterization and analysis of the mechanisms that govern the oil production for Athabasca oil sands in both cases. Finally, in the framework of the numerical methodology presented above the effect of solvent composition and injection rate is illustrated quantitatively in terms of oil recovery efficiency. Recently published data for similar applications are also discussed.

A study of sensitivity to grid size was carried out to define the appropriate grid necessary to represent the near-edge zone of the steam-solvent chamber. Our results for the ES-SAGD process indicate that a decimeter scale is required at least to represent with a good precision the heat and mass transfer processes taking place at the edge of the steam-solvent chamber. These conclusions are illustrated with temperature, saturations, solvent concentration, oil viscosity and mobility profiles from different grid size models applied to ES-SAGD.

It is expected that this work will provide some insight to the simulation community about methodological aspects to be taken into account when hybrid steam-solvent processes would be modeled.

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© Copyright 2014. Society of Petroleum Engineers
Presented at the SPE Improved Oil Recovery Symposium, 12-16 April 2014, Tulsa, OK, USA

SPE Paper #: 
169075-MS
Year: 
2014
Software: 
Process: 
Thermal Recovery