The Bombax Pipeline Project - Installation and Positioning of Large Manifold, Spool Supports and Spool Pieces
Authors: Sokol John , Steffy Mark 
Published: October 2008

The BP Bombax Pipeline Project required the precise installation of some of the world's largest subsea pipeline components in support of BP Trinidad and Tobago LLC (BPTT) gas production at its Cassia Field located offshore the east coast of Trinidad. This work had to be performed to exacting tolerances and within an extremely short schedule in an underwater environment challenged with zero visibility, extreme water currents, and water depths of 225-feet. This paper addresses the installation challenges of this phase of the Bombax Pipeline Project and the methods and equipment that were employed to successfully complete this installation.

Introduction

The Tie-In Work of the BPTT Bombax Pipeline Project (Bombax) involved the offshore installation of a 400- ton subsea manifold, five 70 ton pipe spool support frames, five 48-inch diameter pipe spools (one measuring 300 feet long and weighing 270 tons), five 26-inch diameter pipe spools, two 20-inch pipe spool, a 12-inch hot tap, and approximately 19,000 feet of 6-inch diameter pipeline. The most challenging phases of this tie-in work were the installations of the subsea manifold, the pipe spool support frames and the 48-inch diameter pipe spools.

The installation work took place approximately 64 kilometers offshore the east coast of Trinidad. Prior to the start of the Tie-In Work, the owner, BPTT, had already installed approximately 63 kilometers of 48-inch pipe from the BPTT production facilities at Beachfield, Trinidad to the offshore site at the Cassia Field. The owner had also preinstalled a 26-inch pipeline between platform Kapok and the planned location of the 400-ton subsea manifold. In addition, the owner had recently completed installation of a new separation platform, Cassia B, and a new drilling platform, Kapok. Already existing at the site were platform Cassia A, a 40-inch diameter gas pipeline from platform Mahogany to the BPTT Beachfield production facility, and a 12-inch diameter condensate line from platform Mahogany to the BPTT Beachfield production facility.

The installation work involved several components. The first component was the installation of a 6-inch pipeline to connect the newly installed platform Kapok to the existing 12- inch condensate pipeline that passed through the field. CDI installed approximately 19,000-feet of pipeline between platform Kapok and the 12-inch condensate line where the 6- inch pipeline was connected to the 12-inch line through the installation of a hot tap.

Next in order of installation was the installation of the subsea manifold (see Figure 1). This 400-ton manifold had been constructed dockside in Trinidad and had to be lifted from the dock, transported offshore and installed, all without the benefit of a derrick barge. The offshore installation required precise positioning and placement.

After the installation of the subsea manifold came the installation of five specially designed pipe spool support frames between the subsea manifold and platform Cassia B located approximately 100 meters away. These five support frames were to provide support for the 48-inch pipe spools that would connect the subsea manifold to platform Cassia B.