SPE Reservoir Evaluation & Engineering
Volume 14, Number 3, June 2011, pp. 287-298

Summary

Oxidative degradation of polymers is a serious concern in their field application for enhanced oil recovery (EOR). This study is an attempt to resolve some of the discrepancies in the literature regarding the occurrence and extent of this degradation, as well as to present a coherent framework for discussing the multitude of possible radical reactions. Sodium carbonate and bicarbonate are demonstrated to play a key role in stabilizing polymer against multiple reported sources of degradation, and it seems likely that this is caused by their effect on iron solubility. Brines containing iron in the reduced state are often obtained from aquifers for use in polymer hydration. These brines are shown to be prone to causing immediate degradation if exposed to air during or after polymer hydration because of the oxidation of soluble iron. If this cannot be avoided, preaeration may be a feasible strategy to minimize degradation during hydration. However, care must be taken to ensure subsequent degradation is not caused by the injection of a polymer solution containing oxygen into a formation containing iron. For instance, sodium dithionite can be added downstream of the last exposure to oxygen. The use of sodium carbonate may also mitigate degradation caused by the oxidation of iron (II) during polymer hydration.

© 2011. Society of Petroleum Engineers

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History

• Original manuscript received: 15 June 2010
• Meeting paper published: 25 April 2010
• Revised manuscript received: 15 February 2011
• Manuscript approved: 8 March 2011
• Published online: 16 May 2011
• Version of record: 7 June 2011