What Future for Conventional Pipelay Barges?

Abstract In order to study the evolution of Conventional Pipelay Barges, the paper presents the past and present capabilities of some selected laybarges and how their equipment has been modified to suit the market needs. A second section reviews the pipelay market needs to date and its major characteristics. A segmentation between Conventional lay, Flexible line and Rigid Reel lay is apparent. All three segments grow significantly from 19% to 1997 and remain at a sustained level of activity for the years thereafter. There is a tendency to shift to smaller diameters and deeper waters. The last section discusses the pipe lay barge evolution; it concludes that the fields where the greatest gains can be achieved for the industry seem to be: for station keeping, dynamic positioning; for laying techniques, S-lay: and for production rates, real-time nondestructive control techniques. Introduction Since the Sixties, conventional pipelay barges have dominated the market of pipelaying. This has remained the case, even though considerable innovation and effort has been put into alternative laying techniques such as bottom-tow or near-the-bottom-pull or tow, surface-tow, rigid steel and flexible, reel barge or J-lay. Throughout this period, ETPM has operated conventional pipelay barges, such as DLB 1601, DLB Polaris or LB 200, first on their own behalf, and later for the McDermott-ETPM Joint Venture. The Company is therefore well placed to look back at the various challenges the industry has met up to now to review those it will be facing in the near future, and to outline the improvements and innovations that will be required to adapt to new market requirements. Past & Present Barge Capabilities Present Lay barge capabilities have been largely determined by the successive challenges the industry has had to face. Large diameter trunklines The challenge to transfer large quantities of crude or gas over very long distances, with minimum intermediate boosting platforms, started in the North Sea in the mid Seventies. It sill continues today and extends to other areas as well. Typical characteristics of some selected projects are shown in Table 1. This has resulted in the construction of a different generation of lay-barges able to work in harsh environments, of two types monohull, such as DLB 1601, or semisubmersible, such as the LB 200 (ex Viking Piper) or SEMAC I. These were further upgraded later in time to suit the needs of the market, mainly with regard to tensioning devices, stinger capacities, monitoring and control systems, handling equipment and welding equipment. Further, the water depths in which the pipelines were to be laid increased dramatically with the crossing of the Norwegian Trench (deeper than 350m) which resulted in additional increases in tension and stinger/ramp capacity (see Fig. 1- LB 200 laying Zeepipe IIB for Statoil).