The emergence of new offshore exploration targets at depths of 3,000 metres or more is putting increasing pressure on operators to maintain their deepwater assets, which requires the industry to keep pushing the limits of current technology.
While oil and gas structures, equipment and other high-value components located above the surface require regular inspection and monitoring, subsea assets, located in increasingly deeper water require the same treatment.
While certain subsea inspections can be carried out by professional scuba divers, operators may need to conduct inspections in water that is not clear enough for this to be effective, in highly remote locations or at extreme depths or pressures which would be considered unsafe for divers.
In these cases, operators may opt to instead use unoccupied and highly manoeuvrable remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs).
ROVs are typically connected to a group of cables, or tether, sending electrical signals back and forth between the operator and the vehicle. At minimum, most ROVs come equipped with a camera and lights, but some have advanced tools and features such as mechanical manipulators, sonar, magnetometers, cutting/shearing tools, and other devices to measure characteristics of the environment.
Industry is also increasingly using AUVs in its inspection and monitoring operations. AUVs are self-propelled, unmanned and untethered underwater vehicles capable of carrying out simple activities with little or no human supervision.
In 2017, Total completed the first large-scale inspection survey in the deep offshore using an AUV. Equipped with next-generation sensors, the AUV performed a comprehensive inspection survey of 502 kilometres of pipeline in Block 17 in Angola.
It was a novel, bold approach that enabled the company to create a new strategy for managing subsea pipeline integrity.
Total notes that key to the AUV is its ability to ensure optimised, low-cost inspection campaigns.
“In the medium term, the aim is to obtain a multifunctional resident AUV that can spend several months on the seabed and carry out work on the facilities at any time,” Total says.
Industry and research collaboration
In April 2020, scientists from around the globe, led by Dianne McLean and Miles Parsons from the Australian Institute of Marine Science (AIMS) urged closer ties between industry and researchers to maximise the use of ROVs.
The scientists said ROVs could be adapted from their use in the industry to increase scientific and industry understanding of the impact of marine infrastructure, thus boosting environmental and resource management capabilities using a range of instruments, including audio recorders and sample collectors.
Dr McLean said with some low-cost engineering and operational tweaks, industry and science can use ROVs to fuel new scientific discoveries.
“For instance, we could better understand the influence of structures such as platforms and pipelines in marine ecosystems – to the mutual benefit of the resource company and the environment.”
The new research follows on from an earlier study that used adapted underwater vehicles to examine fish populations around a platform on the North West Shelf, 138 kilometres offshore from Dampier in Western Australia.
In May 2020, the AIMS team extended the study, working with Santos to use ROVs to survey marine life around shallow water platform jackets.
“By partnering with experienced research scientists, industry can improve the quality of its ROV-derived data,” says Dr Parsons.
Dr McLean said the extra information could be particularly useful when it comes to complex engineering and environmental management challenges such as decommissioning large structures at the end of their working lives.
“From an industry point of view,” she said, “these small additions to ROVs and their use for scientific surveys has the potential not only to improve environmental management, but also to facilitate more informed engagement with external stakeholders such as regulators and the public.”
The research shows that small enhancements to the vehicles and how they are used now could provide substantial benefits to science and to resource companies in the long-term.