Shell Gabon is operating and producing oil from numerous fields located in the western part of Gabon.
Crude oil is treated and exported from the Gamba Terminal to tankers through a 30inch offshore export line connected to the SBM (Single Buoy Mooring) via a PLEM (Pipeline End Manifold) and 2 x 16inch floating hose strings (risers). The total length of the existing export line is approximately 10.7km, consisting of 1.3km onshore and 9.4km offshore, from the export pump in the Gamba terminal to the PLEM.
The existing export sealine was installed in 1986 and needed to be replaced as it had reached the end of its design life. The sealine was originally designed as a single line with no provision for inspection, pigging or cleaning facilities. The Gamba Terminal is located about 200NM south of Port Gentil.
In order to improve the operating performance and maintenance, Shell Gabon wanted to replace the single existing line with a looped 22inch sealine system and pigging facilities to allow round trip pig runs for inspection and operational cleaning purposes.
Van Oord Offshore was contracted by Shell Gabon to replace the existing sealine (onshore and offshore), install a new PLEM, rotate a SBM, flush the newly installed system, inspect the SBM and decommission the old PLEM in the Gamba field (200NM south of Port Gentil). Van Oord Offshore contracted Bluestream as their diving sub-contractor for the project. Bluestream was responsible for the preparation and execution of the diving activities which took place from the DSV Stril Server (DP2).
The project scope of work consisted of, but was not limited to, the following tasks:
- Pre-flooding on the pre-installed sea-lines
- Recovery of PLEM tow/hold back wires
- SBM preparation works
- Grouting of PLEM
- Laydown head removal – 4 pieces
- Installation of spools – 4 pieces
- Concrete mattress installation
- Floating hose removal and installation
- Subsea hose removal and installation
- SBM rotation of 60 degrees
- Decommission old 30 inch pipeline and PLEM