The Hannay field is located in Block 20/5c of the North Sea, approximately 150 km Northeast of Aberdeen. The development consists of two subsea producers tied back to Buchan via a 13.5 km pipeline. The production mechanism at Hannay is depletion with significant aquifer pressure support.

The Hannay Field commenced production from a horizontal subsea well (Hannay 1) at an initial rate of 18,000 stb/day. However, the initial months saw approximately 9 tonnes of sand production transported into the production separators.

In an attempt to mitigate sand production, the well was flowed below 10,000 BFPD. Reduced flow rates from the Hannay 1 well provided economic justification for a second producer. Hannay 2 was drilled approximately 1 year after field start-up. Due to sand production from the Hannay 1 well and sensitivity to water-based gravel pack fluid, it was necessary to complete the well with a cased-hole gravel pack. The installation of the gravel pack resulted in a large skin of 100. Acid was used to reduce this skin to approximately 50; however, the Hannay 2 productivity still remained significantly impaired.

This paper presents the engineering studies conducted to evaluate and justify the perforation of the gravel pack in the Hannay 2 well to reduce well damage. These include rock mechanics, sand prediction analyses, and reservoir simulation work to evaluate the potential benefit and optimum interval to perforate to maximise oil recovery.

Detailed well intervention planning was undertaken and successful operations conducted to increase oil production from the well by 3,000 BOPD. Incremental reserves of 1.0 mmstb will be realised for a cost of under £2 million. This shows the importance of a long clean-up period for wells that initially produce sand before adopting a conservative sand control strategy.

You can access this article if you purchase or spend a download.