The BP Bombax Pipeline Project - Design for Construction
Authors: Champagne Brett , Smith Derek , Grass Jerry 
Published: October 2008

The BP Bombax Pipeline Project involved designing and installing one of the largest subsea pipelines of this magnitude in the world to support gas expansion in Trinidad and Tobago. The Bombax Project pipelines and manifold are in an area of relatively shallow water, ranging from around 250 feet at the platforms, gently sloping to the shoreline. Such water depths do not generally present significant problems for pipeline design and installation. With a 48-inch pipeline, however, the effects of wave and current are significantly exaggerated and bearing in mind that with such a large diameter, small variations in material thicknesses have a measurable impact on costs, from steel for the line pipe, to concrete for the weight coating.

The paper focuses on the design for construction challenges involved with the new 48-inch trunkline and how these challenges were addressed. Specific design topics that will be addressed in this paper include: material grade selection, wall thickness design, and stability design. The paper will also focus on the decision by the project to involve the installation contractors during the design phase.

Introduction

In response to the increasing demand for energy in the form of natural gas, BP Trinidad and Tobago has started expanding its offshore fields and gas transportation system to supply new LNG trains at Point Fortin on the West side of Trinidad as well as the increased local domestic market. There are two projects currently underway to expand production and transportation of gas from 1.5 bscfd to 3.0 bscfd, the Kapok Project and the Bombax Project. The Kapok Project comprises a new 2.6 BCFPD production platform, Cassia 'B' that is bridge connected to the existing Cassia 'A' platform and a new drilling platform Kapok. The Bombax Pipeline Project includes 63 km of 48-inch offshore pipeline from Cassia 'B' to landfall at Rustville, on the East Coast of Trinidad. From the landfall, the pipeline extends 1.8 km onshore to the existing Beachfield slug catcher and production facility for onward transportation of gas to the various industries on the island including the LNG facilities on the West Coast. The offshore end of the 48-inch pipeline is connected to the existing 40-inch pipeline via a 20-inch subsea jumper. This jumper facilitates looping of approximately 2/3's of the existing 40-inch pipeline thereby expanding thetransportation system capacity.

Additional gas production to meet the growing industrial demand will be supported by a new wellhead platform located at the Kapok field along with continued development of existing fields. The Kapok platform is linked to the Cassia 'B' production hub by a 26-inch multi-phase pipeline installed as part of the Bombax Pipeline Project. Due to the development schedule, the Kapok platform will be ready for production before the Cassia 'B' hub topsides are available. To allow Kapok to produce early gas, it is intended to carry out separation on Kapok with the test separator and transport liquids via a new 6-inch line to the existing 12-inch liquids line. The 12-inch liquid line transports liquids to shore from BP's existing platforms originating from the Mahogany platform.