An artificial island has emerged as the preferred development option for the 100 million bbl offshore extension of Wytch Farm oil field on the south coast of England.
Field operator BP Exploration hopes to submit planning applications for the island during 1991. Production start-up from the island is provisionally set for 1995.
BP has also started up a new gathering station in the onshore part of the field that will enable production from Europe's largest onshore field to rise to 60,000 b/d from the current 11,000 b/d.
Wytch Farm started production in 1979 from the small Bridport reservoir at 924 m subsea.
In 1986-87, BP started development of the larger underlying Sherwood reservoir at 1,585 m subsea. The project required a new gathering station, 41 wells, a 56 mile, 16 in. oil line to Hamble near Southampton, and a pipeline to deliver gas into the U.K. grid.
First production from new wells, along with oil from older wells, has started to flow to Hamble terminal at about 20,000 b/d. The flow will rise to the field's peak of 60,000 b/d the next few weeks.
That will be followed by the start of associated production of 4,000 b/d of gas liquids and 12 MMcfd of sales gas. Gas liquids will move by rail.
The onshore part of Wytch Farm has recoverable reserves of about 200 million bbl. Most of the offshore extension cannot be reached by drilling from onshore sites.
ISLAND DETAILS
The artificial island concept emerged after detailed talks with many local groups, at which other options for the offshore development were discussed. These included subsea completions, concrete or steel wellhead platforms, a concrete gravity based island, and deviated wells from onshore sites.
The island was preferred to other options because it will be less obtrusive and provide better protection in case of an oil spill. Objections came from the Nature Conservancy Council, which was concerned about the disruption during construction.
Because of the effect of the island on navigation and fishing rights in Poole Bay, BP will need to promote an act of Parliament before it can proceed with a detailed planning application for the project.
The artificial island is to be built 1.2 miles offshore in 2023 ft of water and cover an area of 15 acres. The island will stand 33 ft above low tide level and will be landscaped to screen facilities except for the drilling rig mast.
BP plans to drill 30-40 wells from the site, which is to be permanently manned and linked to the existing Wytch Farm facilities by pipeline.
If there are no delays, the island could start production in 1995 when the 60,000 b/d flow from the onshore part of the field will start to decline.
BP figures offshore production will build slowly to maintain the 60,000 b/d level. Eventually the offshore flow could be 30,000-40,000 b/d.
Preliminary advice on the project has been taken from one of the partners in Wytch Farm, ARCO British, whose parent company operates four artificial islands off California.
WHAT'S NEXT
Now that the island concept has been chosen, BP is concentrating on studies to pinpoint the best site for the unit.
It has commissioned a study by Hydraulic Research Ltd., Wallingford, England, on the effect of the island on beaches and navigation channels.
If this study shows the island will cause silting of local harbors, other development options will have to be reconsidered.
BP owns a 50% interest in Wytch Farm. Partners' interests are ARCO 17.5%, Premier Oil Dorset Ltd. 12.5%, Kelt Exploration Ltd. and Clyde Petroleum (Dorset) Ltd. 7.5% each, and Goal Petroleum plc 5%.
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