Conoco eyes novel floater for Banff field

Banff Development Layout [152962 bytes]

Conoco (U.K.) Ltd. has received U.K. Department of Trade and Industry approval to develop Banff oil field, which is currently undergoing a 6-month production test.

Banff lies in 100 m of water on U.K. North Sea Blocks 29/2a and 22/27a and has estimated reserves appraised to date of 60 million bbl of oil and 39 bcf of associated gas.

Unique design

Conoco plans to produce Banff with a unique production ship, built to the delta-shaped Ramform design originally adapted by PGS Exploration AS, Oslo, for seismic vessels.

PGS operates two Ramform seismic vessels and plans to build two more. The hull shape is thought to give greater stability than conventional hulls, allowing greater vessel uptime in severe North Sea conditions (OGJ, Aug. 28, 1995, p. 72).

For Banff development, Conoco has let contract to a PGS unit, Petroleum Geo-Services U.K. Ltd., to provide and operate a Ramform production ship.

PGS subsequently let contract to Atlantic Power & Gas Ltd., Aberdeen, to operate the field on a day-to-day basis.

Conoco has not disclosed development cost for Banff. However, PGS said the contract will bring it $350 million.

Also, a contract to build the hull has been let to Hyundai Engineering & Construction Co. Ltd., Ulsan, South Korea.

The ship is expected to cost a total $200 million to build, with topsides likely to be added in U.K. Banff is expected on stream in June 1998, with a projected field life of 7 years.

The hull will be only 380 ft long, compared with 700 ft for a conventional vessel of similar capacity. Because of its delta shape, it will still be able to support a 16,000-ton deck load.

The ship will have capacity to produce 60,000 b/d of oil and 45 MMcfd of gas. It will also be able to store 120,000 bbl of oil.

A storage tanker will be moored nearby to hold a further 500,000 bbl of oil.

Iain MacMillan, Banff project manager, said the decision to choose a Ramform ship was not based on vessel shape, but with best commercial value given a similar performance between a standard production ship and the Ramform.

Project details

Oil production is expected to peak at 60,000 b/d, while gas exports are expected to be 20 MMcfd, with a further 5 MMcfd to be used as fuel gas.

Oil will be exported from the storage unit by shuttle tanker. PGS is also considering using two shuttle tankers to offload the oil, with permanent storage only in the Ramform ship.

Gas is to be exported through an 8-km, 6-in. pipeline that will be tied in to the Central Area Transmission System operated by Amoco (U.K.) Ltd. Conoco expects to conclude a gas export deal with Amoco soon.

First production from Banff will come from two development wells drilled for an early production system. Sedco 707 semisubmersible rig will have produced 5 million bbl of oil from Banff at an average 35,000 b/d when it leaves the field this month (OGJ, Nov. 11, 1996, p. 28).

Conoco intends to drill two water injection wells before production resumes and install a five-well cluster manifold on the seabed, to be tied back to the ship with flexible risers.

Reserves earmarked for development to date lie in Paleocene sands and an underlying fractured chalk reservoir at 4,500-7,600 ft. A Conoco official said other structures in the field could be developed later.