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Innovative ROV/ADCP Combination Extends Range
Fugro GEOS Innovation in Gulf of Mexico

Fugro GEOS ADCP/ROV application
Here is the RDI 300kHz ADCP being mounted on the drillship’s ROV. The ADCP has a deep water casing, since it gathered continuous data as the ROV moved from surface to bottom in the 8800 feet of water.

Fugro GEOS had a problem: their client BHP was about to drill the second-deepest well in the world, on the Walker Ridge Block in the Gulf of Mexico. The well was located at a depth of 2680m (8800 feet) in an area where water currents could threaten the marine riser. Traditional ADCP (acoustic Doppler current profiler) current measurement equipment could only reach up a little over 1000 meters in good conditions. What to do?

Get innovative, that’s what.

Fugro GEOS has previously extended the water current profiling ranges by employing two 75kHz ADCPs. One was suspended below the drillship, to cover the top 450m of the water column. The second was mounted on the blow-out preventer on the ocean floor, looking upward, to monitor currents near the bottom. This double configuration has given good data for shallower wells.

But it wouldn’t work in the ultra deep water areas of the Gulf. The real innovation at Walker Ridge was the implementation of a 300kHz ADCP mounted on the drillship's ROV. This ADCP continuously collected current profile information as the ROV descended and ascended throughout the entire water column. One instrument, full coverage of all 2680 meters!

Fugro GEOS developed a special software package that they call RovADCP to integrate the current velocities measured as the ROV descended in the water column. Real-time data was made available to the drillship for the full water column. This data, which can be used alone or combined with data from stationary ADCPs (using Fugro GEOS’ RigADCP software), provides the information needed to safely manage the drilling operation in an area of current activity. Full coverage is especially critical in deep water, where hydrodynamics have an even greater impact on operations (due to increased depth) and the ocean conditions are more variable and less predictable.

ROV and ADCP, ready for deployment underneath the drillship. The ADCP data was interpreted through Fugro GEOS’ RovADCP software.