INTO THE DEEP 10
TECHNOLOGY
ADUS
3D LASER SURVEY Tullow Oil, operating offshore Ghana on the west coast of Africa, has a continuous requirement for more effectively monitoring their seabed infrastructure, which is located in challenging deepwater environments. To this end, ADUS, a newly created department within DeepOcean and working with DeepOcean Ghana Ltd. has recently completed an innovative deepwater subsea 3D laser survey for Tullow Oil. This is the first extensive commercial laser survey of its kind conducted in the industry and it heralds a new era of high-resolution, cost effective subsea data acquisition. ADUS was originally a ‘spin out’ company from the Universities of St Andrews and Dundee in Scotland, specializing in highresolution surveys of shipwrecks that were subject to large-scale wreck removal and management projects. Notable ADUS wreck surveys included the Deep Water Horizon in the Gulf of Mexico, the Costa Concordia in Italy, the Rena in New Zealand, and the Sewol in South Korea. ADUS was acquired by DeepOcean in 2013. So what are the end results of a laser survey? Laser surveys produce high-resolution 3D metrical datasets which can be ‘flown around’ on a computer screen or even ‘walked through’ by the user at the right scale in Virtual Reality (VR). This allows for an appreciation of the asset and its context in a way not previously possible. The datasets then lets the user derive accurate measurements in context for metrology purposes and to understand more precisely the changes over time of any
particular asset, which is an important part of the inspection process. For the Tullow work, the ADUS survey operations covered 12 drill center locations and a total of 27 metrologies in water depths between 800 and 1800 meters, setting new bench marks for high-resolution contextual 3D surveys whilst proving to be an alternative and rapid ‘contactless’ solution to conventional (LBL) metrology surveys. Tolerances requested were +/- 10 cms in position, +/- 10 cms in height, and +/- 0.5 degrees in orientation (heading, inclination). The achieved results were well within these tolerances. In fact, the measurements achieved over a 25-meter distance using the 3D point cloud were within 1 cm of the distances measured using the traditional LBL acoustic system. A key aspect of this survey was the fact that it was conducted dynamically - i.e. from moving ROVs, rather than stationary ones. The dynamic approach, whilst very much more complicated to achieve, offers many advantages over a static laser deployment. The survey is rapid and able to cover much larger areas, and allows for optimal placement of the laser to acquire the best possible data on complicated structures. The dynamic laser survey solution, from a moving ROV is comprised of 2G Robotics deep rated ULS 500 Pro Lasers and Sonardyne’s SPRINT INS system. The performance of these systems exceeded expectations with accuracies approaching 1cm in dynamic operation. Two deep rated ULS500 systems and the Sonardyne system have now been purchased by DeepOcean.
The accurate 3D ‘point clouds’ resulting from the survey, coupled with innovative modeling techniques developed in house, are providing DeepOcean engineers with valuable quantitative and contextual information to better inform IMR tasks and undertake metrology tasks, thereby increasing efficiency for the client. The success of these recent survey operations has led to a further contract under which the company will conduct similar surveys on Tullow’s assets off Ghana for the next two and a half years. There are, of course, many other potential subsea applications for the use of the laser which will be of value to DeepOcean’s existing clients. Anyone reading this who considers that use of the laser would add value to any particular project, or might wish to include the techno-logy in future tenders, should get in touch with either Mark or Stuart Leather. Future development of the laser system includes: • • • • •
Utilization of dense point cloud laser data for reverse engineering tasks Providing a basis for superior visual asset management systems Use of virtual reality for enhanced data processing and enhanced inspection Use of virtual reality for operational simulations Use of HD still photographs derived from the laser system camera for co-registration with point cloud data