Delving Deeper with AUVs
By Ross MacLeod
What lies beneath? Subsea industry to delve deeper with underwater robotics
Autonomous underwater vehicles (AUVs) and buoyancy-driven gliders have revolutionized the way the subsea industry gathers oceanographic data and despite the volatility of oil prices, it is predicted that the demand for this technology will continue to grow over the next five years and beyond. Although the sustained low oil prices have reduced budgets and put a cap on the development of new technology, operators are quickly beginning to realize the cost saving benefits of underwater gliders forcing them to rethink their approach to subsea exploration.
Saving Time is Saving Money
Gliders are the latest step in the development of autonomous float technology. Unlike conventional propeller driven AUVs, they don’t require a vessel on-site and can be deployed for up to six months without having to resurface. They are also much smaller and lighter, making them easier and quicker to transport and mobilize for international operations.
Historically, remote operated vehicles (ROVs) or divers have been used for underwater research activities, however these methods are far more complex and can take many weeks to plan and deploy, often requiring large numbers of personnel and big budgets.
In the current market where this is no longer a viable option for many companies, gliders ability to operate without human intervention, eliminating the safety risks attached to operating ROV vessels, makes them an increasingly attractive alternative to the subsea industry.
The first subsea gliders were highly specialized and were limited in scope to the specific task that they were designed to complete. Since then, technology has progressed allowing them to become dynamic platforms for a variety of imaging, chemical, biological, acoustic and oceanic sensors that can be adapted to meet the needs of a specific project.
During the 1990s, AUV technology entered an intense research and development phase which was largely funded by national defense agencies, with commercial vehicles not widely available until around 2000.
Today, with advances in technology, gliders operate with little or no need for powered systems and are typically used offshore to investigate environmental, metocean or water-mass structures.
Ashtead Technology, a leader in marine technology and subsea services, has been an exclusive distributor of Blue Ocean’s fleet of Teledyne Webb Research Slocum gliders since striking a global asset management agreement last year with the provider of ocean data solutions.
Blue Ocean’s Slocum gliders can be equipped with a diverse range of different sensors and can be deployed in the water for up to a six months at a time. With two-way satellite communications the gliders can be deployed and controlled anywhere in the world, are highly weather resilient and have no environmental impact.
Conceived by Douglas C. Webb and supported by Henry Stommel, Slocum gliders were named after Joshua Slocum, the first man to single-handedly sail around the world.
The long-range and duration capabilities of Slocum gliders make them ideally suited for subsurface sampling, they can be programmed to transmit their data to shore while downloading new instructions at regular intervals.
The small relative cost and the ability to operate multiple vehicles with minimal personnel and infrastructure enables small fleets of gliders to study and map the world’s most dynamic seas.
Slocum gliders operate using buoyancy as a propulsion mechanism, which allows for longer deployment periods and the collection of large datasets continuously over these extended time scales.
They are capable of transmitting data in real-time and can be deployed and recovered easily, at a fraction of the cost of traditional vessel-based or fixed-mooring monitoring approaches, lowering both project costs as well as health, safety and environmental risks.
Initially gliders were used extensively for academic and military applications but over the past few years, they have been increasingly adopted for a wide variety of oil and gas applications including pipeline leak detection, oil spill response, decommissioning studies, dredge/construction plume monitoring, environmental monitoring and metocean studies.
Over time gliders have become more and more autonomous with less human interaction required as artificial intelligence has advanced.
To meet the long-term needs of the subsea industry, current developments are focused on increasing battery life, improving autonomous functions and enhancing sensor capabilities so they can perform increasingly challenging intervention tasks.
This will see gliders play an important part in the dismantling of offshore structures as decommissioning activity steadily increases over the next decade.
They will also allow decommissioning work to be carried out as cost-effectively and safely as possible, either replacing or supporting ROVs and diving operations in monitoring and mapping the environmental impact.
It’s believed that gliders will develop faster than the 30 years it took ROVs to become everyday tools, and with software and sensor improvements, they could truly transform the way the industry conducts underwater installation, inspection, repair and maintenance work.
The current generation of gliders are capable of exploring water depths of 1,000m, travelling at approximately 1-2 nautical miles per hour.
Future developments in glider technology could see them operate with long endurance, extreme depth, or rapid response capabilities, while development of new sensors will further expand the parameters that can be measured.
It is clear that gliders will continue to play an increasingly important role in the exploration and monitoring of the world’s oceans.
Their capabilities have already surpassed what was once believed as possible, travelling across complex terrain to collect high resolution metocean data to satisfy monitoring requirements for a number of industries including subsea, offshore renewables, mining, engineering and environmental.
The continued development of gliders and sensors will increase the range of marine applications, while advances in artificial intelligence will increase reliability and flexibility.
Blue Ocean Monitoring recently completed a contract in Indonesia working for PT Newmont Nusa Tenggara (PTNNT), which is a subsidiary of Newmont Mining Corporation, one of the world’s largest gold producers with assets and operations across five continents. The task was to utilize the Slocum glider for monitoring in support of PTNNT’s Tailings Placement Program at its Batu Hijau copper-gold mine in Sumbawa, Indonesia. The program involved tailings from the mine being piped (3.2 km) offshore and deposited off the continental shelf, where the depth reaches in excess of 4,000m. The glider equipped with a suite of water quality sensors was deployed to monitor the tailings which were not being disbursed into the coastal environment of Sumbawa. The monitoring program took just three weeks to complete and satisfied the full objectives of the survey scope.
(As published in the October 2016 edition of Marine Technology Reporter)