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. Introduction The Hannay oil field is located 13.5 kms Northwest of the Talisman operated Buchan field. The discovery well 20/5c-6, drilled in June 1996 by Amerada Hess, encountered an oil bearing Lower Cretaceous Britannia Sandstone Member. Two drill stem tests were then carried out, producing 3,700 - 8,000 bopd. The first development well, 20/5c-8y (Hannay 1) was completed over the A and Massive sands with 5 ½" tubing.The total perforated interval was 755ft over a horizontal section of 1,235ft, with a cemented 7" liner. The well tested at a peak of 21,900 bopd.The 20/5c-8x sidetrack was required to be plugged back following severe operational problems when running the 4–1/2 inch liner. The Hannay Field came on-line on 21stMarch 2002, producing through an 8-inch pipeline to the Buchan Alpha platform.From Buchan oil is exported through a 12-inch pipeline to the BP operated Forties field and onwards via the 36 inch Forties Pipeline System to Cruden Bay. The initial months of production from Hannay 1 saw rapid water cut development accompanied by approximately 9 tonnes of sand production.Due to sanding, production from Hannay 1 was restricted and a second development well, Hannay 2, was planned to recover the reserves not recovered by Hannay 1 when the 8x-sidetrack was abandoned. The Hannay 2 development well (Hannay 20/5c - 9) was spud on 20th March 2003.The low angle well was located to target the local high to the east of the Hannay 1 sidetrack (20/5c-8x).This well location recognised the potential upside of the central high and was selected based on maximum forecast incremental reserves from simulation work in addition to reasonable proximity to the existing Hannay well to minimise geological risk. Although it was originally intended to complete the well with an open- hole gravel pack (OHGP), based on the initial sand production seen in Hannay 1, core testing identified that the Barrier Shale was highly sensitive to water-based gravel pack fluid.It was subsequently decided to complete the well with a cased-hole gravel pack (CHGP). Prior to installing the CHGP the casing was perforated at intervals in the A sands, and the massive sands to within 20 ft above the OWC.
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 p roduction 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.
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