Claudio Paschoa compares two new compact ROV-operated systems for seabed geotechnical drilling by Forum Energy Technologies and Helix Energy Solutions.
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Forum’s Rovdrill 3 system. |
New compact ROV-operated machinery for seabed geotechnical drilling, coring and sampling are being developed for deepwater operations. This new form of geotechnical drilling combines work class ROV systems with compact drilling systems. Two companies, Forum Energy Technologies and Helix Energy Solutions, are leading the way in the development of this technology.
An advantage of taking the coring and sampling rig to the seabed is to minimize deck operations and a decrease in deck footprint. This dramatically reduces the inherent risks associated with these types of activities, while at the same time greatly reducing costs, by taking the traditional drilling rigs with their high dayrates from the picture.
The rig itself can be very compact, easy to deploy, operate and recover without the need of specialized and expensive surface vessels or platforms, and once deployed, they are free from the influences of sea state conditions and vessel/platform motions during sampling operations. However, the surface deployment of the systems, are still dependent on sea and wind state.
Forum Energy Technologies has employed its Rovdrill 3 system worldwide. This is Forum’s third generation Rovdrill system, which is composed of a purpose-built drilling unit controlled by a WCROV Rovdrill. Designed and built as a collaborative effort between Perry and GEMS (Geotechnical Engineering and Marine Surveys) engineers, Rovdrill has a proven capability to perform applications for offshore geotechnical investigations and mineral explorations.
Rovdrill provides many advantages over standard drillship operations, as it is compact, easy to deploy, operate and recover. Forum’s Rovdrill can be operated from a variety of ROV systems and vessels of opportunity without the need of specialized and expensive surface vessels or platforms. It also has the advantage, according to Forum, of being capable of operating in all seabed environments with multiple, interchangeable rig foundation options. This flexibility may help in optimizing core sample quality. Rovdrill is capable of operating in water depths up to 4000m. The coring/sampling depth is a standard 90m, but is expandable to 200m.
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Helix’s ROVdrill Mk 2. |
A different concept is proposed by Helix Energy Solutions, which fundamentally attaches the ROV to an extremely compact subsea coring and sampling rig. Helix’s system, the ROVdrill Mk. 2 actually places the ROV and the rig inside a cage. Helix Energy Solutions Group, Inc.’s robotics subsidiary, Canyon Offshore Ltd. (UK), which has an extensive fleet of proven trenching equipment and ROVs, is responsible for the ROVdrill Mk.2 systems and operations.
The ROVdrill Mk. 2 can be used for geotechnical site investigation recovering samples down to 50m below the seabed and carrying out cone penetration testing (CPT) to over 120m. The system also allows for a fully automated seabed operated drilling module capable of carrying out a range of coring, sampling and in situ tests. It is launched as a conventional work-class ROV system from a DP2 vessel, albeit the combined weight of the ROV and drilling unit and its linear disposition may limit its maneuverability. However, this may be balanced by the fact that currents won’t affect the ROV’s operation.
The self-contained system is capable of drilling and testing with full real-time monitoring of the operation, via cameras and subsea sensors. ROVDrill’s tool racks are configured to provide a total of 14 tool slots, with each slot able to carry 3 tools, for storing as many as 40, 3m long tools for various applications. The ROVdrill Mk. 2 system can be deployed from any suitable DP vessel. However, differing from Forum’s Rovdrill 3, it cannot use a ROV of opportunity as its ROV and the subsea geotechnical drilling rigs are interconnected. Both the Forum Rovdrill and Helix’s ROVdrill MK. 2 are deepwater operations-capable.
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