Abidjan : assistance to shore crossing for a gas pipeline

The field has a potential of 2.5 billion barrels of crude oil and 3,300 billion cubic feet of natural gas.

During phase 1 of the BALEINE project, Geocean was involved in setting up the subsea infrastructure for the installation of a gas pipeline between the Baleine field and the Abidjan power plants. The pipeline would transport the associated gas and enable the production of electricity, which would be connected to the local distribution network.

A micro-tunnel was drilled to allow the subsea pipeline to pass from the sea to land in the heart of Abidjan’s urban area to achieve this.  The project was carried out in partnership with Bessac, another Vinci Construction entity specialising in the construction of underground tunnels and micro tunnels.

Operations were complicated by waste at the bottom of the water, regularly blocking the pump suction. Despite this, the team managed to keep the operations on time to be ready for the arrival of the customer’s pipelay barge’s, which would build and lay the pipeline. Time was of the essence !

BALEINE project landfall and shore approach mission :
Installation engineering – design and supply of installation aids.

• Preparation and mobilisation in Abidjan of a pontoon adapted to the operations to be carried out, dredging/lifting/diving.
• Dredging of the seabed (5,000 m3) to allow recovery of the MTBM Microtunnel drilling unit (50 tonnes) and the future gas pipeline entry into the tunnel during installation.
• Installation of a 4″ diameter, 1,550 m long traction cable across the 350 m microtunnel linking land and sea, laid on the seabed to a depth of 20 m off the coast of Abidjan. This will enable the pipeline to be pulled from a laying barge.
• Assistance with the pipeline installation by pulling along the seabed using a 500-ton linear winch located on land at the end of the tunnel.