Page 648 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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FIGURE 23.5
SeaTrepid’s Riser Crawling vehicle.
With the autonomous riser crawler, the vehicle is mated to a subsea docking station (Figure 23.6(a)). The docking station is linked to the host platform via power and data communica- tions. The vehicle communicates wirelessly with the docking station. Upon command, the vehicle departs the docking station, travels the length of the riser, and then redocks (after inspection) with the docking station for both dumping data gathered during inspection and for battery recharge (Figure 23.6(b)). This method isolates the vehicle’s locomotion energy requirement to simply trav- eling the length of the riser (thus avoiding the considerable energy requirement for station-keeping in a subsea current).
23.3.2 AUVs
The next step in AUV incorporation is to remove them from structural support, giving them a full free-swimming capability. But to what level can such autonomous systems be incorporated into the offshore environment?
For some time now, AUVs have been used offshore for environmental and geophysical surveys. One of the more successful companies performing AUV surveys for the oil and gas industry is Lafayette, LAbased C&C Technologies. With their line of C-Surveyor vehicles, based on the Hugin AUV developed by Kongsberg, C&C has cornered the market for pipeline route and site sur- veys in support of deepwater exploration and development. As of this writing, C&C is approaching 125,000 miles (approx. 200,000 km) of surveys for over 60 clients (and climbing!). The question posed in the early days of AUVs entering the offshore industry was whether their use would be profitable. An AUV surveying at 46 knots can conduct a survey an order of magnitude faster than an ROV operating at less than 1 knot—or the now-rather-rare towed vehicles. A recent con- tract that C&C signed with Petrobras was for 730 days of support for a $50 million price tag!
The prior data shows that the AUV is the tool to use when conducting oil and gas exploration and pipeline surveys, however, what role would they play around the offshore rigs, platforms, and installations? Lockheed Martin believes AUVs can play a significant role in this area as they can,
23.3 Autonomous ROVs 649
