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    Deepwater drives construction vessel upgrades

    Vessel & ROV News // June 1, 2001
    A small-scale revolution is taking place in the offshore construction market, with operators rushing to upgrade the construction vessels that they use to carry out heavy lifts and lay pipelines for the worldwide offshore industry.

    In the last six months, three of the major contractors working in this field - Stolt Offshore, J Ray McDermott and Heerema Marine Contractors - have all completed major upgrades of their construction vessels in order to target the growing amount of workin the burgeoning deepwater sector of the offshore industry.

    For Stolt Offshore, the market driving the need to upgrade its vessel - the self-propelled multi-purpose derrick lay barge Seaway Polaris - is the West African market. Although some of the fields off the coast of West Africa are in shallower waters, manyof the more recent finds are not.

    Prior to the upgrade, the Seaway Polaris was best known as a highly efficient shallow water vessel, equipped to DP3 standard, and capable of station keeping in 60kt head seas and 30kt beam seas.

    In order to work more efficiently in heavy seas it was decided to equip her with a new 'J-lay' tower, new outrigger for heavy modules (machinery used to lower large underwater modules), and new facilities for remotely operated vehicles (ROVs).

    Having been fitted with the new equipment, she is now capable of heavy lifts of up to 14,500kN on Floating Production, Storage & Offloading (FPSO) platforms, SPARs and Tension Leg Platforms. The six working stations with which she is equipped enable herto lay pipework at a high lay rate using the S method and a steep curved stinger or the J-lay technique, and the 5,000kN outrigger enables her to lower the largest, heaviest modules.

    A spokesperson for Stolt Offshore said the installation the new 'J-lay' system on the Seaway Polaris was completed in March of this year. Immediately afterwards deepwater tests were successfully concluded and the vessel departed for the Girassol field inBlock 17 offshore Angola, where the Seaway Polaris's first job saw her install a total of 34.9km of 12in water and gas injection lines in an average water depth of 1,350m. Subsequently she has been engaged on the La Ceiba development on behalf of TritonEnergy in Equatorial Guinea, tying back four subsea wells to a FPSO in water depths of 700-900m.

    J Ray's McDermott's upgrade project has seen the derrick barge DLB16 upgraded to an advanced reel/pipelay/derrick barge, whilst Heerema Marine Contractors has upgraded its deepwater construction vessels DCV Balder and DCV Thialf. Both of the latter beingcontracted by BP of the installation of deepwater pipelines in the Gulf of Mexico even before their upgrades were completed.

    As Albert Ploeg of Heerema's marine department explained, Balder has been converted into a Class 3 dynamically positioned deepwater construction vessel capable of using an 800m J-lay system. She also has dual cranes for heavy lifts to set topsides, and amooring line deployment winch capable of installing 6in lines with a line pull of 275 tonnes. Like the Seaway Polaris, she has been tailored to the installation of FPSOs, SPARs, TLPs and integrated topside of up to 6,300 tonnes.

    For its part, J Ray McDermott says the upgraded DLB16 will be capable of a wide range of deepwater operations, having been upgraded to DP2 rating and fitted with a quartet of azimuthing thrusters. The newly upgraded platform will be capable of installingumbilicals and flowlines, along with coiled tubing and reeled pipe, says the company. The work on the DLB was completed at Talleres Navales de Golfo SA del CV (TNG), a subsidiary of J Ray McDermott in Veracruz, Mexico.

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