Operators in the U.K. North Sea have placed a flurry of relatively small fields on production.
Five U.K. fields involve four subsea completions and one wellhead platform tied back to existing platforms.
In addition, Amoco (U.K.) Exploration Co. started production from Davy and Bessemer fields in the southern North Sea, both developed using a minimum facilities platform design that may be copied for other projects.
In the Norwegian North Sea, production from Norsk Hydros Oseberg oil field passed the 1 billion bbl milestone.
U.K. activity
Off the U.K., Amerada Hess Ltd. saw first oil from South Scott field, Conoco (U.K.) Ltd. drew first gas from Ganymede and Callisto fields and from the Kx reservoir, and Phillips Petroleum Co. U.K. Ltd. started gas production from Alison field.
South Scott, in Blocks 15/21a and 15/22, has estimated reserves of 60 million bbl of oil. It began flowing from one subsea well tied back to Scott platform 4.5 km away on Block 15/21a.
Sandy Paterson, project manager, said a second production well will be spudded before late December using a semisubmersible rig. Two water injection wells will be drilled next year.
The first well achieved an initial flow rate of 20,000 b/d of oil.
Paterson said development costs for South Scott are expected to amount to about 65 million ($100 million).
Amerada also is working to develop its Telford discovery, which lies southeast of the Scott platform on Block 15/22, with first oil slated for the end of 1996. Telford holds estimated reserves of 50 million bbl of oil.
Amerada intends to submit a development plan to the U.K. Ministry of Industry & Energy in a few weeks. The plan is said to involve two subsea manifolds in Telford, 6 and 10 km from the host Scott platform.
Conoco developed Ganymede field with an unmanned wellhead platform on Block 49/22, handling gas from five wells. Ganymede reserves are estimated at 250 bcf of gas.
Callisto field has a single well subsea tie-back to the Ganymede platform, 13 km away. Callisto, in Block 49/22, is estimated to hold 70 bcf of gas.
Gas from Ganymede and Callisto moves through a 20 km, 18 in. pipeline to join the Lincolnshire Offshore Gas Gathering System (Loggs), which ships gas to shore at the Theddlethorpe terminal.
Total production from Ganymede and Callisto is expected to average 300 MMcfd. Development cost for the two fields was 120 million ($190 million).
Conocos Kx reservoir in Block 49/16 is one of two reservoirs known officially as Alison field, although the main reservoir in Block 49/11a was developed by operator Phillips.
Phillips and Conoco developed Alison and Kx using a three slot subsea manifold. Alison and Kx were connected to export infrastructure via a subsea tee installed earlier by Phillips during development of nearby Ann field.
As with Ann, gas from Alison and Kx is sent by pipeline to join the Conoco-operated Loggs complex, while operation is controlled by means of an umbilical from Phillips Audrey B platform, 15 km away on Block 48/15a.
Alison is expected to produce 400 MMcfd of gas. The Alison production well is the first trilateral well in the U.K. North Sea. Development cost was 22 million ($35 million).
Kx reservoir holds estimated reserves of 30 bcf of gas, which Conoco said makes it the companys smallest development in the North Sea. Production from Kx is expected to average 20 MMcfd.
Davy, Bessemer monotowers
Amocos platforms in Block 49/30a Davy field and Block 49/23e Bessemer are the first monotower units installed in the U.K. North Sea. Combined development cost is 84 million ($130 million).
Davy and Bessemer are expected to produce a combined 220 MMcfd of gas, with output sent through two pipelines to Amocos Indefatigable platform on Block 49/23a.
Amoco plans to use the same platform design on three other prospects in the same area, due to be drilled this year. They are North Indefatigable, West Davy, and Bell prospects (OGJ, Mar. 27, p. 30).
Amoco drilled a new pool wildcat in North Indefatigable prospect last April. The company is reviewing commercial potential of the resulting discovery.
An evaluation of 3D seismic data from the Bell prospect is near completion. Amoco is considering development options, including use of a small monotower platform or a subsea tieback to the Bessemer export line.
Oseberg production
Cumulative oil flow from Norsk Hydros Oseberg field passed 1 billion bbl Oct. 4. This equals the volume of reserves estimated for the field when the company presented a development plan to Norways government in 1983.
Now Hydro expects to produce a further 1 billion bbl of oil from Oseberg, along with about 100 billion cu m of gas.
Commercial production of Oseberg gas depends on the outcome of a debate under way over which Norwegian fields will be tapped to meet new contracts to supply gas to European buyers.
Operators are expected to make their recommendations to government next month. Oseberg gas competes with gas from North Sea Troll field and Aasgard fields in the Norwegian Sea for development under the gas supply contracts (OGJ, Oct. 9, p. 29).
Gas from Troll field has been injected into Osebergs reservoir, by means of a small subsea development in Troll, since 1991. This injection is expected to help recover an added 315 million bbl of oil from Oseberg during the fields life.
Long term, Oseberg oil recovery will be diminished if the fields gas reservoirs are not depleted.
Oseberg oil production, started in December 1988, amounts to more than 500,000 b/d from three platforms at present.
Osberg field lies in Norways Blocks 30/6 and 30/9. License partners are operator Norsk Hydro 13.68%, Den norske stats oljeselskap AS 64.78%, Saga Petroleum AS 8.55%, Elf Norge AS 5.77%, Mobil Development Norway Inc. 4.33%, and Total Norge AS 2.88%. Copyright 1995 Oil & Gas Journal. All Rights Reserved.
