Fugro GEOS Inc. has been contracted to provide real-time, full water column current measurements for BP’s Gulf of Mexico Thunder Horse production, drilling, and quarters (PDQ) semisubmersible. The PDQ semi is the largest production drilling quarters semisubmersible in the world.
To meet the challenge, Fugro GEOS had to accomplish a number of “firsts.”
The contract involved building the first self-contained 38-kHz acoustic Doppler current profiler (ADCP), which is capable of the longest profiling range ever achieved, Fugro says. The ADCP is suspended beneath the surface of the Thunder Horse platform on a custom-built frame, measuring to depths of over 1,000 m (3,281 ft).
“The design included the repackaging of all the electronics into a subsea housing and the installation of a ruggedized cable to the surface for power and data transmission,” says Caroline Nicholas, sea systems division manager. “Thermal analysis was undertaken to ensure that the electronics did not overheat in the subsea housing.
“Another first was the installation of the cabled mid-water 75kHz ADCP,” Nicholas says. “Installed 500 m (1,640 ft) above the seabed in 1,860 m (6,102 ft) of water, the ADCP was contained in the biggest buoyancy buoy ever produced - a 1.9-m (76-in.) buoy of 1,814 kg (4,000 lb) buoyancy. Our third ‘first’ was the installation of the first cabled seabed 75-kHz ADCP in 2000 m (6,567 ft) of water.”
The 75-kHz ADCPs were lowered from the vessel with ROV assistance and attached to a preinstalled mud mat. Data and power connections then were made using ROV wet mateable connectors. To ensure data transmission over long distances, 5,500 m (3.4 mi) of fiber-optic cable was used.
The system provides real-time full current data updates every 10 min to Fugro GEOS weather monitor software. The data is then displayed through the Fugro GEOS ADCP data acquisition and management system.
