SPE Production & Operations
Volume 24, Number 1, February 2009, pp. 43-49

Summary

Effective matrix acidizing in Kuwait’s horizontal openhole wells is a big challenge. Reservoir heterogeneity and the length of the horizontal wells make acid placement and diversion difficult, particularly in high-water-cut (WC) wells in which water has broken through as a result of high-permeability streaks or natural fractures. Furthermore, acid penetration is limited by the large surface area of the horizontal wellbore, and this is exacerbated by the relatively small injection rate imposed by the use of coiled tubing (CT). To make matters worse, formation damage in horizontal wells is usually very deep as a result of long exposure times.

This paper discusses the application of a new viscoelastic-surfactant (VES)-based, self-diverting acid system for stimulation of more than 20 horizontal openhole wells in carbonate reservoirs in Kuwait. The application also deployed a new nonparticulate material that forms a highly viscous plug when it contacts water and that degrades when mixed with oil in the formation. The new fluid system is pumped before the acid treatment to effectively prevent the acid from stimulating high-water-saturation sections.

The field results show significant improvement in post-stimulation production, owing to effective diversion and water-production control compared with wells in which a conventional polymer-diversion technique was used in the past with no consideration for water-production control in high-WC cases. The new technique has been selected as the standard stimulation practice in most horizontal openhole carbonate wells in Kuwait.

© 2009. Society of Petroleum Engineers

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History

• Original manuscript received: 28 November 2006
• Meeting paper published: 11 March 2007
• Revised manuscript received: 18 June 2008
• Manuscript approved: 13 October 2008
• Published online: 2 March 2009
• Version of record: 26 February 2009