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BG International's Blake Project Will Set World Record.

Early last year, Coflexip Stena Offshore was awarded a substantial E.P.I.C. contract by BG International for the Blake Development that will see the largest and heaviest reeled pipe system installed and operating in the world. The engineering and project management phase is nearly completed and in this article we look at just what is involved on this complex project.

The Blake Field is located in water depths of 95 meters, approximately nine kilometers north of the Ross Field in the Moray Firth of the Northern North Sea. The field is operated by BG International on behalf of partners Talisman UK and Paladin Resources, and is to be tied back to the existing Ross FPSO Bleo Holm. The Ross field came on stream in April 1999 and the subsea infrastructure was designed, manufactured and installed by CSOL. Ross field production is projected to continue around 25,000 bpd and the addition of Blake plateau production of 44,000 bpd was seen as a natural development for the Ross FPSO.

Installation of the subsea infrastructure began in early April with production kicking off in mid-June.

The base case development plan for Blake is to be six production wells clustered around a manifold and two satellite water injection wells some three kilometers on either side of the main well cluster, to maintain aquifer pressure and hence production rates.

The manifold serves to distribute lift gas, injection water, control functions and chemicals to the wells and to route individual well production to either or both the 10-inch and 12-inch production/test pipelines to Ross.

The manifold will be connected to the Ross FPSO by the following new services: 10-inch production; 12-inch production; 6-inch gas lift; 12-inch water injection; and dynamic/static umbilical carrying power, communications and chemicals.

In turn, the satellite wells are each served by a six-inch water injection flow-line and umbilical. A new, dedicated control system is to be installed on the FPSO.

Critical to the Blake Development is flow assurance, that is to say the production pipelines must be capable of carrying the hydrocarbons during the critical early production period and turndown conditions. As the flowing wellhead temperature is close to the wax appearance temperature, high levels of insulation are required on the production pipelines to prevent wax formation which would restrict flow.

A key feature in CSOL's technical solution will be the use of a 10-inch in 16-inch pipe in pipe solution, to maintain the FPSO arrival criteria in terms of arrival temperature.

The use of this type of system has been a result of a substantial development program undertaken by the Group's Offshore Engineering Division based in Aberdeen, Scotland. Once the 10-inch in 16-inch pipe in pipe system is installed, it will be the largest and heaviest reeled system installed and operating in the world.

It is intended that the Blake gross production, at a maximum of 100,000 bpd, will be routed to the production separator and the lower Ross production to the test separator. As such, well testing in the normal manner will not be possible and downhole gauges and multiphase flowmeters, located in the Blake manifold, are required to gather well and reservoir information to optimize field performance.

As it is imperative to maintain reservoir pressure, injection water has to be provided at a maximum flowrate of 120,000 bbls a day, with a maximum of 70,000 bbls a day to an individual well.

At the Ross FPSO, the existing risers will be reconfigured to accept, separately, Ross and Blake production fluids with water injection and lift gas being tied into an existing distribution manifold, located within the FPSO swing circle.

The new dedicated control system will require installation of the new topsides control and power units to provide power, electric and hydraulic, and to communicate with the subsea system, issuing commands and receiving data. In turn, each subsea tree will have a dedicated control module to operate the valves and to receive and transmit data back to the FPSO. New electro-hydraulic umbilicals will be provided through DUCO (a wholly owned CSO subsidiary based in Newcastle) to support the control system.

The manifold (circa 200Te) will be a gravity-based structure designed to house all the pipeline headers and diversion valves and to protect them from danger caused by fishing activity.

The existing Ross FPSO cannot provide the entire Blake requirements in its current state, requiring extensive modifications, in excess of anything that could be carried out with the FPSO in location. It is therefore planned that, during the second quarter 2001, the FPSO will be disconnected, (i.e. the risers and mooring chains) and towed to the McNulty Fabricators conversion yard (a wholly owned CSO subsidiary as of January) where it is expected to be upgraded within a six-week period before being towed back to the field and reconnected.

The management of this phase of the works will be a key factor in the overall success of the project and CSOL anticipates that it will have up to six vessels in the field at any one time to support the disconnection and reconnection of the FPSO.

During the period that the FPSO is off location, the Blake field infrastructure will be installed in what will be a carefully sequenced operation, utilizing the CSO Apache and a number of other CSO DSVs and support vessels. After the successful installation and commissioning phase, the Ross and Blakefields will be brought on stream.

Critical to such a multi-faceted project are the interfaces between all the participating contractors, BG International, Talisman and the statutory regulating authorities. Interface Management will be undertaken by a dedicated team led by CSOL, which will ensure that each participant knows what and where the interfaces are and what is expected from them. Without this management function, this project, with a large number of participants, would not be possible.

CSOL, as E.P.I.C. subsea contractor, will also require the support of a large number of specialist subcontractors and supply chain management will be fundamental to secure the best solution for the Blake Development. CSOL has developed over the years a number of relationships with key vendors to ensure that best practices and quality of service are provided. This is well-recognized within the industry with ten projects involving tieback/production through an FPSO in the North Sea, over the last four years, eight including Blake will have been carried out by CSOL.

The Blake project is typical of the developments that are now taking place in the North Sea where an all-around approach is required by the E.P.I.C. contractor to ensure that the technical and commercial challenges are met.

Derek Alexander, Project Manager, Coflexip Stena Offshore, Aberdeen, Scotland
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Title Annotation:construction of underwater gas pipeline.
Comment:BG International's Blake Project Will Set World Record.(construction of underwater gas pipeline.)
Author:Alexander, Derek
Publication:Pipeline & Gas Journal
Geographic Code:1USA
Date:Aug 1, 2001
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