More oil and gas operators are turning to compliant tower designs for deepwater development projects.
McDermott Inc. unit Hudson Engineering Corp., Houston, is drafting preliminary compliant tower designs for deepwater developments in the Gulf of Mexico and North Atlantic Ocean.
One unit under design could be used as the hub production facility for staged, multifield development of discoveries in the Atlantic about 190 km west of Shetland Island. British Petroleum plc last month received U.K. Department of Trade & Industry (DTI) approval of a first phase development scheme for 250-500 million bbl Foinaven field, the first west of Shetlands (OGJ, Nov. 14, Newsletter).
The other compliant tower design Hudson is working on as a development option is a 100-200 million bbl discovery on Garden Banks Block 260 by operator Amerada Hess Corp. and 50-50 partner Oryx Energy Co., Dallas (OGJ, Apr. 4, p. 39).
Hudson says compliant tower based offshore production systems are competitive with deepwater production alternatives because the structures can support large deck payloads and high production rates while retaining significant developmental flexibility. The company has performed preliminary designs of compliant towers for water as deep as 3,000 ft. The North Atlantic around Foinaven field is 1,300-1,600 ft deep and the gulf 1,650-1,700 ft deep at Garden Banks 260.
FOINAVEN FIRST PHASE
BP's $860 million first phase Foinaven development is expected to start producing by late 1995 or early 1996. Production is to peak at 85,000 b/d of oil, with gas being reinjected.
Cumulative first phase Foinaven production is expected to total about 200 million bbl. DTI approved Foinaven's first phase development a little more than a month after conclusion of a 44 day extended well test (EWT) last summer that confirmed the field's commerciality. A horizontal well during the EWT flowed an average 17,800 b/d of oil and at peak 20,000 b/d.
BP's development plans call for Foinaven subsea wells to produce through flexible flow lines to an FPSO permanently stationed in the field and anchored to the seabed with a turret system allowing the vessel to rotate 360. Foinaven's flexible flowlines and control umbilicals are to connect subsea wells and manifolds to the FPSO turret. Production is to be exported from the field via shuttle tankers.
Finnish built supply vessel Anadyr is to be converted at the Astanos fabrication yard in northern Spain to store 300,000 bbl of oil. Gas lift and gas/water injection facilities are to be installed on the vessel.
A group led by McDermott and Golar-Nor has a contract for design, engineering, procurement, and operation of the FPSO production system and shuttle tanker service. Contracts worth more than a combined $140 million have been awarded for manufacture and installation of subsea trees, controls, flowlines, and risers. A study by Smith Rea & Associates concluded other discoveries in the area could be developed with FPSOs. If later discoveries add sufficient reserves, a pipeline link to an existing terminal might become a commercial option. However, Smith Rea found the long term mix of production facilities could include fixed, floating, and compliant structures, all supported by significant subsea elements.
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
