BP has been using autonomous underwater vehicles (AUVs) in anger since collecting seabed survey data in the Gulf of Mexico four years ago with a Hugin 3000, developed by Norwegian subsea specialist Kongsberg Simrad and marketed by Louisiana-based C&C;Technologies. That BP are among the faithful when it comes to further refining AUV technology to be ‘enhancing and enabling' can be seen in recent collaborative projects aimed at making advances in areas including intelligent pipeline survey software and hovering inspection and intervention AUV units.
‘We believe that there are some fundamental things that we can add to existing technical solutions through the enhancing use of AUVs - essentially carrying out the work of ROVs but standing on their own,' stated BP offshore systems team EPT senior subsea engineer David Saul. ‘Equally, we are looking at AUVs as enabling because we see developments coming up in the future that will simply not be operable without AUV technology, many examples of which will be in the sub-ice and ultra-deepwater categories.'
BP, he said, has adopted a bifocal view of subsea technology, ‘looking both at what we need now, and what we will need in the future. And we are doing this by having a series of step developments'. The emphasis is on technology development that will see commercial spin-out. ‘We want to create staged products that people can go out and sell to give the confidence to oil companies to move to the next stage subsea,' offered Saul.
‘This approach also helps when the technology gets to the enabling stage later down the piece because the people using it will be familiar with it,' he added. ‘There are no big surprises, no step-changes in operation.'
Collaborating with Subsea 7 and SeeByte, BP in 2001 launched a project with the mission of creating a commercially viable intelligent pipeline survey tool. Designed at the same time to support BP's own AUV development goals, the project's product - Autotracker software - from Heriot-Watt University spin-off SeeByte, last year reached the trial phase.
Autotracker, its makers claim, makes it possible for an AUV ‘to search for, locate, identify, and then track a pipeline while gathering video and other sensory data'. Because the software can ‘recognise' changes in pipeline position and re-plan its forward course, noted Saul, ‘at the end of the run you have a survey of the pipeline not a survey of the seabed where the pipeline was supposed to be or where the AUV drifted off to'.
In a trial last year in the UK North Sea off Sullom Voe, which followed on from earlier tests off Orkney, a Subsea 7 Geosub AUV outfitted with Autotracker software carried out more than 100km of runs, including successful simultaneous auto-tracking of multiple pipeline sections, collecting survey data while travelling at a speed - ‘typically' 4 knots - that would leave most ROVs in its wake while navigating rock dumps and free span areas.
The hope, said Saul, was that Autotracker-powered AUVs would be deployed this year in the US Gulf. ‘The business unit that backed funding for this project have made clear that they want to use it again next year,' he noted. ‘We feel it works and we are going to take this opportunity to advance intelligent pipeline tracking.'
Through another collaboration with Subsea 7 and SeeByte, known first in 2004 as Spinav and since rebranded SeeTrack Offshore, the oil company is angling to fashion ‘a safe platform for early de-risking of a hovering AUV - one of the long-term goals at BP'. SeeTrack, an embedded software application that enables a workclass ROV to provide fully autonomous survey and inspection of a moving riser in strong currents, is designed to free the ROV pilot to focus on inspection or intervention activity while affording ‘safer access to more critical and harder to reach areas'.
In recent trials on the Foinaven field West of Shetland, a 75m riser section was inspected with the aid of the tracking system using autonomous DP controlled position-holding in up to 1.6knot crosscurrents.
BP's most ambitious AUV project to-date took place last year in the US Gulf with ECA's Alistar 3000, a 3000m water depth capable unit powered by lithium ion batteries and designed for ‘close flying' operations around subsea structures and equipment (OE October 2006). ‘The goal was to evaluate and demonstrate just what are the state-of-the-art capabilities of hover-capable AUVs,' Saul said. ‘We really want to go and clarify the commercial opportunities here - and assess current weaknesses.'
Put through its paces both in a location in the Mediterranean and, later, on BP's US Gulf King field, the compact, 5m long AUV, which weighs 2100kg in air including its 150kg payload of inspection equipment, carried out several missions performing pipeline tracking at various depths and speeds - as well as hovering, the Alistar 3000 cruises at 2.5knots and has a top velocity of 6knots - before moving on to a series of anomaly and anode inspections.
Casting forward, Saul saw two areas of challenge in the realm of AUVs: ‘people and technical'. ‘From the work we have done with ECA, Geosub, Autotracker, and so on, we feel we know where we stand in terms of areas of technical improvement,' he stated. ‘We need to improve positioning, communication and reliability, and we need to look at alternate recovery systems.' As across the offshore industry, skills shortages are a stumbling block to the AUV sector, ‘a niche area that not a lot of people know about'.
The next step in BP's stepwise AUV development programme will be the creation this year with Subsea 7 of a ‘prototype inspection vehicle', a unit being given life to work as a ‘platform that will allow BP to go and de-risk a number of the activities that will help us to know what we will need technically going forward.'
BP's present AUV wishlist includes improved 3D DP, ‘AUV-friendly' advanced tracking sonar and video systems, wireless vessel-to-vehicle data communications, and enhanced battery capability. Doubtless the list will roll on as technological breakthroughs are made and, at the same time, offshore demands on AUVs grow more onerous.
‘People are talking about AUV/ROV hybrids; what AUVs could do toward enabling sub-ice operations; long-term deployments; change detection,' catalogued Saul. ‘The good news is that to get there we can start by borrowing some technology and thinking from ROVs, so there are wins to be had here.
‘The best approach is stepwise rather than the big step: small steps with commercial spin-outs get a lot more interest from companies when it comes time for trialling technology,' he concluded. ‘AUVs are going to enhance rather than replace existing technologies, but there are going to be clear areas where AUVs will provide core enabling technology.'
by Darius Snieckus
© 2007 Offshore Engineer