The design included the repackaging of all the electronics into a subsea housing, and the installation of a ruggedised cable to the surface for power and data transmission. Thermal analysis was undertaken to ensure that the electronics did not overheat in the subsea housing.

The 38kHz ADCP, which claims to be capable of the longest profiling range ever achieved, is suspended beneath the surface of the Thunder Horse platform on a custom built frame, measuring down to depths of over 1,000m in real-time.

This represented the first installation of a cabled mid-water 75kHz ADCP. Installed at 500m above the seabed in 1,860m of water, the ADCP was contained in the biggest buoyancy buoy ever produced, a 76in buoy of 4,000lb buoyancy. Also ‘first’ was the installation of the first cabled seabed 75Khz ADCP in 2,000m of water.

Installation of the 75khz ADCPs was carried out using an ROV vessel. The ADCPs were lowered into position from the vessel with assistance from an ROV, which attached the subsea ADCPs to a preinstalled custom mud mat. Data and power connections were then made using ROV wet mateable connectors. To ensure data transmission over such long distances,  some 5,500m of fiber optic cable was used, running from the seabed to the Thunderhorse PDQ platform.

The system provides real-time full current data updates every 10 minutes to Fugro GEOS weather monitor software which is then displayed through the Fugro GEOS ADAM (ADCP Data Acquisition and Management) web-based system.

‘We undertook beam analysis to orient the ADCPs and to avoid obstruction of any interference from other subsea structures, and to ensure good quality data was delivered to the client, said Fugro GEOS sea systems division manager Caroline Nicholas. ‘Extensive testing has been done and we have found good correlation between all the instruments, which all agree with each other.’