Supporting Subsea IMR with Resident ROV Systems to Reduce Vessel Days and Carbon Footprint

The offshore oil and gas industry has been investigating innovative solutions to help reduce or eliminate carbon footprints subsea and increase worker safety on- and offshore. Remote operations coupled with advanced autonomous solutions can have a significant impact on how business is conducted.

A recent Rystad Energy report from March 2021 states that inspection, repair, and maintenance (IMR) operations are ideal for robotic operations: “The segment [is] where adoption of robotics has gained the most traction among operators in recent years.”

“The next generation of robotics solutions is already emerging within subsea IMR in the form of perpetually underwater robotics solutions that offer significantly lower costs and better reach than a conventional remotely operated vehicle (ROV),” the Rystad report said.

LIBERTY E-ROV

Launched in 2017, Oceaneering's Liberty™ E-ROV is a self-contained, battery-powered, work-class vehicle that allows performance of routine tasks that would normally be performed by an ROV and support vessel. It can carry out IMR, commissioning, and underwater intervention scopes. It is an all-in-one deployable and recoverable system that comes with a cage-mounted battery pack, tether management system, and communications buoy that stays on the water’s surface to interface with Oceaneering’s Onshore Remote Operations Centers (OROCs) via satellite or 4G LTE mobile broadband.

With its 550 kw Lithium-Ion battery pack, Liberty has the endurance to stay submerged for prolonged periods ranging from 180 days in hibernate, 22 days in observation, and 3-8 days for intervention tasks. Between missions, the Liberty has a quick turnaround on deck for charging and maintenance, and then re-deployed for the next mission.

The Liberty system can also be viewed as a deployment method with packaging that can serve any vehicle shape and size, all depending on the needs.

Once Liberty is deployed subsea by a vessel of opportunity equipped with a subsea crane, the vessel can be relieved. By removing dedicated ROV support vessels, operators can simplify logistics, costs, and reduce their carbon emissions output by an estimated 90%. Operators can have instant availability to use a work class ROV without any installation of topside equipment.

Since its launch, the Liberty E-ROV has achieved many milestones with its 80 missions and more than 10,000 operational hours and contributed to eliminating 7,200 Support Vessel Hours, 28,800 Offshore Crew Hours and 13,700-ton support vessel CO2 emissions.

Key advantages of the system include:

• Reduces vessel days required to complete operations
• Supports efficient installation and recovery operations as the system can be moved using a single lift
• Very low idle power consumption enables the system to be on site for an extended period supporting the launch of the vehicles well in advance of operations
• Reduces carbon footprint and mobilization
• Enables expedited intervention with positioning at strategic locations subsea
• Operated independent of surface weather conditions
• Operations supported by remote piloting at Oceaneering OROCs

During 2019-2020, Oceaneering studied how to improve the efficiency of the Liberty operations by eliminating the need for a typical vessel with subsea crane to support deployment. The study centered on using an emergency preparedness vessel that is present on any field in operation. Several challenges, including safeguarding the vessel’s primary function (responding to an emergency) were solved alongside the client and vessel owner through design and adapting operational procedures.

Today, the Liberty is only deployed from the emergency preparedness vessel using a special-built launch and recovering system (LARS) with an advanced tandem lift active-heave compensated subsea crane offering a safe working load of 34 ton. The LARS is also used to deploy other subsea assets to the seabed (i.e., tooling) and opening hatches on subsea templates. This adds to Liberty’s success and demonstrates how close industry cooperation aiming for a win-win can shape “out of the box” solutions.

CASE STUDY

In 2020, a major operator prepared to commence oil production from a North Sea asset and wanted to ensure that no unplanned incidents occurred during start up through the riser. The operator adopted a comprehensive pipeline seabed-to-platform monitoring plan to maintain the highest level of oversight.

The Liberty E-ROV was selected over a conventional system to complete monitoring at depths up to 310 m several times per day over the course of 1-2 months, depending on the findings. A conventional ROV system would have been vulnerable to stoppage during inclement weather windows and would require extensive effort for multiple deployment and recoveries across the monitoring window. If an additional vessel were required, this would add significant cost and generate additional carbon emissions.

Because the location of the work scope was fixed on the platform area, the Liberty system was deployed in a tethered configuration. A dedicated umbilical provided power and data communication connectivity directly from the platform to the ROV system. This solution eliminated the need to recharge Liberty’s batteries and negated the risk associated with winter storms in the area that may push the system’s buoy out of location.

Liberty completed 822 hours of monitoring spread over 110 top-to-bottom trips conducted across 34 days. The vehicle did not need to dock in the subsea garage and did not require maintenance. No issues were detected during production commencement. This deployment proved Liberty’s ability to provide longer, continuous deployments.

FUTURE DEVELOPMENTS

The Liberty system is continuously being improved through lessons learned. Development plans involve creating a deepwater Liberty system with a depth rating of 3000 m—currently Liberty is rated to 1000 m. A deepwater solution would use existing subsea infrastructure instead of a buoy for communications and charging.

There are also plans for full electrification with the state-of-the-art resident technology developed with the Freedom Autonomous Vehicle. The current Liberty is a full work class ROV system, but the mentioned resident Freedom technology can be tailored and packaged to serve specific needs enabling an even more cost-effective solution. A “lighter” version of the Liberty could become an integral part of subsea installations to perform specific need-based intervention tasks. Such solutions will aim to achieve residency for more than 12 months, preferably matching planned maintenance intervals where a support vessel would be onsite.

For more information, visit: www.oceanneering.com.

This story was originally featured in ON&T's May 2022 edition. Read more, here.