Contaminated water is not normally disposed of offshore, but this was the recent stipulation by the authorities at Abu Dhabi's Das Island. Environmental regulations required corrosive effluent in produced water from a de-oiling plant on the island be reinjected into an aquifer at sea. Coflexip Stena Offshore was selected by operator ADMA-OPCO to supply and install the 6.3 km, 10.75-in. ID water line.
The flexible flowline was laid between existing pipelines, starting from a flange pit on the island. The first 600 meters of the line from the shore were buried, with the remainder set down on the seabed, terminating at a wellhead tower.
CSO's flowline was manufactured at its plant in Le Trait, northern France, then mounted onto six reels which were shipped to the UAE on a heavy lift vessel. The pipe was fabricated using high density polyethylene thermoplastic liner, to provide protection against corrosion, plus suitable flow and abrasion resistance.
Criteria for the design included shallow water stability on the seabed (10-30 meters) and upheaval buckling resistance for the buried section. Local subcontractors were employed for the onshore work and offshore trenching. CSO has now supplied over 200 km of flexible pipe for offshore projects in the Middle East.