Buoyancy tanks assist shallow-water Bahrain jacket installation
Aqualis Offshore has completed offshore installation engineering of an 1,800-ton steel jacket structure offshore Bahrain for the Bahrain LNG Import Terminal project.
The company worked on this program with APMC, which was responsible for transportation and installation on behalf of the EPC contractor, GS E&C.
Aqualis’ scope covered engineering services related to the load-out, transportation and float-off operation, towing, positioning, lowering to the seabed, and buoyancy tank removal, including all marine procedures.
The offshore installation was completed last month.
To ease the jacket installation in shallow water, the company engineered buoyancy tanks that allowed the jacket structure to be floated-off the transport vessel, towed to site, and lowered to the seabed through ballasting.
This approach avoided the need for mobilizing a large installation crane vessel.
“The jacket, with three of six main piles slotted into the jacket legs, and its buoyancy tanks were loaded out onto pre-installed grillages on the [Wish Way] submersible heavy-lift vessel using trailers,” said Phil Lenox, director – Asia Pacific, Aqualis Offshore.
TheWish Way transported the jacket from the SKMT (Samkang M&T) Goseong yard in South Korea to its final location offshore Bahrain in 20 m (65.6 ft) water depth.
“On arrival, the heavy-lift vessel was ballasted down for the jacket to be floated off at a suitable nearby site and towed 5 km [3.1 mi] to the installation location in shallow water,” Lenox continued.
“Following positioning between the breakwater and jetty structure, the buoyancy tanks were ballasted to lower the jacket to the seabed. After driving the main piles, the buoyancy tanks were removed from the jacket structure by releasing connecting pins and de-ballasting the tanks for recovery.”
The associated topsides float-over installation is due to follow in August.