Installation of Deepwater Pipelines With Sled Assemblies Using The New J-Lay System of the DCV Balder
Authors: Wolbers Dick , Hovinga Rob 
Published: October 2008

This paper describes the most important features required for installing deepwater pipelines, pipelines with in-line sled assemblies, PLETs, and SCRs. This includes methodologies specifically developed to suit the capabilities of DCV Balder. During the last quarter of 2002, Heerema Marine Contractors (HMC) performed an extensive Trials program proving all pipelay methodologies and associated installation procedures of the DCV Balder. This included the installation of 10 km 28-inch and 24-inch pipe with a Pipeline End Termination (PLET) and an in-line sled assembly.

Subsequent to successful completion of these trials, the DCV Balder started with installation projects which included the installation of in-line sled assemblies with weights up to 136 mT.

Introduction

In the past ten years, major oil companies extended their exploration activities more and more into deeper water offshore areas, driven by portfolio considerations and the depletion of their easily accessible reservoirs.

Heerema Marine Contractors (HMC) decided to respond to these market trends by setting up and executing a deepwater investment program to convert the Semi-Submersible Crane Vessel (SSCV) Balder into the Deepwater Construction Vessel (DCV) Balder.

Features of the DCV Balder specification include the 1050 mT capacity J-lay system and a 650 mT A&R winch, which in combination with the world's largest Mooring Line Deployment winch provides the unique capability to lower pipelines with loads up 1200 T. The combination of the J-lay tower with the two main cranes of the DCV Balder allows for handling of large structures such as PLETs and in-line sleds complete with mudmats.

Maintaining its existing heavy lifting capacity results in the following main benefits:The ability to use one vessel to execute all marine installation works for a complete Deepwater Field Architecture including the export system, thereby eliminating intermediate mobilizations, mode changes, interface risks, and multiple mobilization charges.The ability to install deepwater flowlines and export pipelines (up to 32-inch OD) with PLETs and in-line sled assemblies of up to 150 mT in water depths exceeding 2000 meters.The ability to install Steel Catenary Risers (SCRs) and alternative risers concepts with special care for fatigue life considerations. DCV Balder is presently working for the BP Southern Green Canyon/Mississippi Canyon Deepwater development in the Gulf of Mexico. The Scope of Work comprises of the installation of the complete infrastructure for four major deepwater fields and associated deepwater export pipelines. This would not only include 330 km of export pipelines and 100 km of flowlines, but also 20 in-line sled assemblies and fifteen Steel Catenary Risers (SCRs). A typical deepwater field layout is presented in Figure 1.

Recently completed projects include the installation of a 6.5-mile pipeline with an in-line sled assembly weighing 136 mT.

This paper presents the specification and use of the DCV Balder's enhanced capabilities, and the development of the revised working practices adopted by HMC. In addition, HMC's Quality, Environment, Safety, and Health (QESH) Management System applied on all deepwater installation projects will be addressed.