Editor's note: This story first appeared in the July-August 2022 issue of Offshore magazine. Click here to view the full issue.
By Alan Anderson, Jami Cheramie, and Casey Glenn, Oceaneering International
The case for developing an autonomous and resident subsea vehicle to perform offshore infrastructure inspections is evident. For example, in the North Sea, there are dozens of fields and associated pipelines located within 100 km of the coastline.
The development of a new generation of resident and autonomous underwater vehicles (AUVs) has been enabled thanks to advances in secure, reliable communication networks, software, batteries, and positioning sensors. These new vehicles can accurately position themselves subsea and receive missions to gather data and safely send it back to shore for analysis without resurfacing.
Oceaneering’s Freedom AUV can carry out survey, commissioning, and inspection, maintenance, and repair scopes without requiring a pilot to monitor and control operations. Freedom can be easily launched from shore to service subsea assets, dock subsea as a resident vehicle, recharge, and transfer data, and move between fields to support other assets as needed.
Recently, Freedom achieved its latest milestone, completing pipeline inspection in an operational environment. It is set to begin commercial campaigns in 3Q 2022.
Oceaneering has been at the forefront of development and market release of autonomous and resident vehicles for the last two decades. The company launched remote piloting and control technology (RPACT) in 2004, allowing the flexibility to pilot remotely operated vehicles (ROVs) from shore. After launching the Liberty E-ROV in 2017, Oceaneering began work on designing an autonomous resident vehicle that combined the work class functions of an ROV and the speed, range, and maneuverability of an AUV.
Increased 4G offshore coverage along with faster, stable, and more cost-efficient satellite communications have supported more flexibility for remotely piloting from shore. Additionally, more offshore installations have direct fiber to shore connectivity, resulting in lower latency and higher fidelity connections.
With a docking station on the seabed, Freedom is capable of operating in an autonomous and tetherless configuration. The vehicle boasts a working range of 120 km, a working depth rating of 4000 m, top speed of 3 m/s, and subsea deployments of up to six months.
Freedom can inspect miles of flowlines and remote wellheads as it flies around the field. The vehicle, like the company’s Liberty E-ROV, can be remotely piloted from a remote operations center while in tethered, free-swimming mode. While in autonomous mode, free of the tether, its advanced autonomous software enables high quality, unpiloted inspections of infrastructure.
Freedom’s software enables the vehicle to complete low altitude inspections for pipeline surveys. The vehicle can track pipelines down to two meters off the seabed to provide high-resolution data survey altitudes and up to 20 m for reconnaissance.
This configuration of the vehicle enables pipeline tracking with unprecedented proximity and tolerances, providing significantly improved data acquisition. However, tracking a pipeline this closely adds complexity. To compensate, the software includes a heightened level of obstacle detection, autonomous obstacle avoidance, and situational awareness. These features allow the vehicle to re-plan its route and re-engage with the tracked pipeline. Freedom has been outfitted with numerous sensors in its configurable payload bay. This includes machine vision cameras, Sonardyne’s SPRINT-Nav 500 inertial navigational system, Voyis underwater laser scanner ULS-500 Pro, and Teledyne’s Reson T20 imaging sonar.
Freedom’s control software recognizes pipeline features including free-spans, depleted anodes, mattress crossings, and anomalies. Freedom’s ability to stop and hover, especially when related to anomaly detection, enables the software to trigger sub-missions for further inspection, thus avoiding the requirement for costly subsequent inspection operations after the initial survey.
The team has focused on the continual advancement of the system’s pipe tracking and sensor fusion algorithms throughout the software development process. Increased focus has also been dedicated to achieving the highest-possible quality of data for customers while advancing work in subsea obstacle avoidance and object of interest inspection routines.
Software reliability and failover tolerance are areas where the team has achieved marked improvement. The intensive qualification process also has put a large focus on reliability engineering and potential hazard identification. Findings from live testing at Oceaneering’s dedicated facility in Norway and three campaigns on operating pipelines have supported the development of the company’s reliability engineering. This in turn helps ensure that learnings are continuously rolled into the product as part of the continuous improvement process.
To ensure that the Freedom AUV meets its specifications and durability, a rigorous testing schedule was required involving thousands of kilometers of tracked pipeline including obstacle avoidance and over 300 autonomous docking operations.
In March 2019, Oceaneering started its Living Lab, an autonomous vehicle test ground near Stavanger, Norway, devoted to the development, testing, and verification of the new control software and the next-generation vehicle. The site allowed for thorough reliability testing in water depths up to 300 m, replicating an offshore environment with subsea docking station and a variety of pipelines at depths ranging from 10-240 m.
In June 2020, the vehicle began testing untethered, demonstrating its ability to dock and undock autonomously in a relevant environment. In September 2020, Freedom completed the industry’s first autonomous subsea docking operation using a third-party underwater docking station at the test facility.
Testing in an operational environment began in late February 2021, assessing all autonomous features of Freedom on a real pipeline in a sheltered location. Another objective proved was the hydro-acoustic control for supervised autonomy and subsea launch and recovery into the docking cage using machine vision and advanced autonomous docking algorithms. In August 2021, Freedom started demonstration on offshore pipelines in the UK and Norwegian sectors. During this testing, Freedom accurately and quickly tracked pipelines at low altitudes, enabling the collection of much higher fidelity data.
Freedom is currently undergoing final qualifications with further commercialization actions and additional resident docking tests are being demonstrated on behalf of a customer.
In future developments, Oceaneering will be looking to integrate more historically ROV-centric tasks within Freedom’s autonomous behaviors, including cathodic protection measurement, leak detection localization, measuring depth of burial of pipelines and cables, and valve position assessment and operation.
Freedom is well-suited to support future developments, including the subsea factory concept where rigs and vessels are not primary assets. It is anticipated that with continued development and customer buy-in, Freedom can be used for infrastructure assurance, light intervention operations, cleaning, torque tool functions, manipulator-based activities, and underwater inspections in lieu of drydocking operations.
