The Magazine for Underwater Professionals
Autonomous underwater vehicles: operational experience and the future
Autonomous underwater vehicles have been gradually gaining a foothold in the offshore industry over the last 20 years. AUVs are primarily used for survey operations. They have recently gained a higher public profile with the coverage of the search for flight MH 370 in the South Pacific. However, opinions over AUVs tend to be mixed in the oil and gas industry; AUVs have both ardent supporters and deep sceptics. The AUV may be ready for the industry, but is the industry ready for the AUV?
The Aberdeen Branch’s November 2014 evening meeting focused on this question. A number of speakers discussed the development and current status of AUVs in the subsea oil and gas industry. The presentations looked at low and high logistics AUVs, their capabilities, their applications and their advantages over traditional survey methods. Both contractor and operator perspectives were covered.
The meeting was chaired by Damian Ling from the Chevron subsea survey team. Damian has extensive operational experience with AUVs at Chevron, and chaired the meeting in a well-informed and assured manner. Damian first introduced Stuart Inglis from Subsea 7, who gave a short presentation on the Aberdeen Branch SUT+ group and its plans for 2015.
The first technical speaker for the evening was Simon Goldsworthy, business development manager at NCS Survey Ltd. Simon presented NCS’ operational experience with the small, low logistics Gavia AUV, manufactured by Teledyne Gavia. The Gavia is a relatively small modular AUV, typically deployed in a configuration of around 3.5 metres in length, 20 centimetres in diameter and a weight of 120 kilograms. The NCS business strategy is to use vessels of opportunity to support its AUV operations. Simon described a range of operational modes, including a two-man beach launch, a fast rescue craft (suitable for calmer weather, outside the North Sea), a small host vessel using very simple launch and recovery methods and a large host vessel with a cradle launch and recovery system developed by NCS.
NCS started its AUV survey business in 2009. The operation grew slowly at first, but has become a successful survey business. Simon described some of the challenges which NCS has faced in developing its AUV capability, including NCS’ own operational learning and improvements in the reliability and uptime of the AUV. Low logistics AUVs are widely supplied in military operations, characterised by a high supply of vehicles of low specification, and little support from the manufacturer. In contrast, oil and gas applications are characterised by a low supply of AUVs but with high specification, and a high demand for the manufacturer’s support. Simon explained how the engagement of the manufacturer is critical to optimising the AUV for oil and gas survey operations. Simon completed a very open and interesting presentation with a summary of NCS’ future development plans and a request for support from the operators to define their future requirements, to assist the industry with development direction.
The next speaker was Andy Docherty, offshore AUV manager at DOF. Andy described DOF’s experience with the higher logistics Hugin AUV, manufactured by Kongsberg Maritime. The Hugin vehicle is intended for deployment from a larger host vessel with its own dedicated trolley/stinger launch and recovery system. DOF started its AUV operations with the Hugin 3000 AUV in Norway, operating as part of the Geo Consult business, which was later acquired by DOF. Geo Consult/DOF operated the Hugin 3000 up to 2008 when it was lost in Western Australia. DOF subsequently replaced the vehicle with the newer Hugin 1000, and has since built up an extensive and impressive track record with the AUV.
Like NCS, DOF also uses vessels of opportunity, but the larger logistics demands require a containerised logistics system which can be mobilised onto suitable vessels. Andy noted the importance of the vessel and its mobilisation; vessels of opportunity vary widely and the right vessel specification and equipment is critical to the success of the project. DOF has completed more than 20,000 kilometres of line survey since October 2012. Typically, the Hugin runs on 18- to 20-hour missions with launch and recovery operations once a day. DOF has recently ordered an updated Hugin 1000 with updated specification, including hot-swap hard disk drive data storage to reduce turnaround times, and plans to update the existing Hugin 1000 to the same specification. Andy closed his very simulating presentation with some operational lessons learned by DOF, and by summarising DOF’s plans for the future.
The third speaker was Jonathan Mueller-Wiesner, subsea operations engineer in BP’s North Sea operations subsea and pipelines team. Jonathan gave an overview of BP’s operational lessons from pipeline landfall inspections with a small low logistics AUV. His presentation was based on most recent BP landfall inspections (2013) conducted with a small AUV in north east Scotland and Shetland, up to five kilometres offshore, in water depths inaccessible by offshore vessels. Jonathan focused on the operability of AUVs in a subsea execution framework and the readiness of AUVs as a standard subsea inspection tool. Jonathan noted that, on paper, the AUV has the potential to be cheaper than other survey methods, to reduce the execution risks and to obtain data closer to the beach line. In practice, the mobilisation was easy and the AUV performed well in strong tides and shallow water. However, progress was slow due to reliability, launch and recovery (which was limited to flat calm seas from the small host vessel) and the need to repeat surveys due to the partitioning of the survey route. Jonathan acknowledged that BP would repeat inshore surveys with AUVs, but would ensure that their lessons learned were addressed in future operations.
Jonathan also explained that BP is not ready to perform offshore AUV pipeline surveys in the North Sea and is looking for better reliability and wider weather windows for launch and recovery. Jonathan gave a very honest and engaging summary of AUV performance from the operator’s perspective.
The final speaker of the evening was Jim Jamieson, technology manager/life of field at Subsea 7. Jim’s presentation was titled ‘The Autonomous Inspection Vehicle (AIV)’. Subsea 7 has replaced the word ‘underwater’ with ‘inspection’ to identify a number of key developments in its vehicle capability. The Subsea 7 AIV is a medium-sized ROV-shaped vehicle with dimensions of 1.7 metres by 1.3 metres by 0.8 metres. Like an ROV, the vehicle has the ability to hover and hold station and is suitable for all types of infield inspection. A key technology is the feature-based navigation capability (developed by Seebyte Ltd) which allows the AIV to interpret its environment and compare against its own mission “world model”. The AIV can adjust its own mission to suit the actual environment that it encounters.
Jim described how the AIV is deployed from a seabed basket, therefore avoiding the critical launch and recovery at the water surface. The AIV can return to its own basket, dock safely and wait to be recovered later, therefore removing the schedule dependency on vessel operations. Jim explained how Subsea 7 has identified a number of operational modes, including deployment from a host facility, simultaneous operations from construction vessels working in the area and the self-explanatory “lobster potting” operational mode where more than one AIV and basket can be deployed by a single support vessel. Each AIV completes its mission from and back to its basket, while the support moves between baskets to recover, recharge and redeploy each AIV in turn.
Jim concluded his very absorbing presentation with some personal comments on the future of autonomous technology and how it can be developed towards full autonomous intervention in the underwater environment. Jim explained the road map using a simple “see-sense-touch-do” model. Current autonomous vehicles can “see” their environment, and are beginning to “sense” it too, with advanced sensors. The next challenge is to “touch” the environment; while this may seem a simple operation in human terms, it is a significant technical challenge to develop the interaction, feedback and sensitivity to allow controlled contact with other features. Once achieved, then the door is open to the final “do” step, and the possibility for simplified intervention activities. The technology and road map are impressive. However, as Jim explained, it has to make economic sense to become reality.
The evening concluded with Damian Ling’s thanks to the speakers, for four fascinating and high quality presentations. The evening raised many questions from the floor and much thought provoking discussion. Launch and recovery are clearly important challenges, but AUV technology is definitely here, ready and available, and has an exciting future ahead.
One of the key questions of the evening was put to Andy Docherty of DOF, namely, has the AUV replaced the ROV for survey operations? Andy replied that the AUV is faster and lower cost than an ROV, but the ROV can still perform operations that are not yet within the capability of an AUV; for example, the Hugin single head MBES cannot provide the same level of data density as the dual head ROV. Some of these misgivings will be overcome in the future as the AUV industry develops more ways to close the gap, as has already been done with positioning accuracy and data repeatability. The AUV is not intended to replace the ROV but to provide a viable alternative.
We were delighted to see a high turnout, with 165 attendees at the event who enjoyed further debate in the bar and over the buffet dinner provided by the Treetops Hotel. As always, our grateful thanks are due to the speakers and our branch sponsors Fugro, GE Oil and Gas, KD Marine, Nautronix, OneSubsea, Technip and Wood Group Kenny.