SPE Reservoir Evaluation & Engineering
Volume 16, Number 1, February 2013, pp. 51-59

Summary

Foam is a means of improving sweep efficiency that reduces the gas mobility by capturing gas in foam bubbles and hindering its movement. Foam enhanced-oil-recovery (EOR) techniques are relatively expensive; hence, it is important to optimize their performance. We present a case study on the conflict between mobility control and injectivity in optimizing oil recovery in a foam EOR process in a simple 3D reservoir with constrained injection and production pressures. Specifically, we examine a surfactant-alternating-gas (SAG) process in which the surfactant-slug size is optimized. The maximum oil recovery is obtained with a surfactant slug just sufficient to advance the foam front just short of the production well. In other words, the reservoir is partially unswept by foam at the optimum surfactant-slug size. If a larger surfactant slug is used and the foam front breaks through to the production well, productivity index (PI) is seriously reduced and oil recovery is less than optimal: The benefit of sweeping the far corners of the pattern does not compensate for the harm to PI. A similar effect occurs near the injection well: Small surfactant slugs harm injectivity with little or no benefit to sweep. Larger slugs give better sweep with only a modest decrease in injectivity until the foam front approaches the production well. In some cases, SAG is inferior to gasflood (Namdar Zanganeh 2011).

© 2013. Society of Petroleum Engineers

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History

• Original manuscript received: 19 October 2011
• Revised manuscript received: 13 August 2012
• Manuscript approved: 7 November 2012
• Published online: 31 January 2013
• Version of record: 27 February 2013