While oil and gas operations have multiple critical assets above ground that require attention, there are also plenty below the surface that need to be maintained, such as offshore platforms and drilling equipment, pipelines, communication and other cables.
Subsea inspections are generally performed during the installation and decommissioning stages of a project, but they are also critical during the operational phase. During these inspections, operators will examine assets for leaks, cracks and other damage that may occur as a result of corrosion, aging, seismic events, installation issues or damage caused by a third party. Failing to do so proficiently could cause both severe environmental impacts and financially damaging product losses.
Certain visual inspections can be carried out by professional scuba divers with high quality still or video cameras, providing benefits such as flexibility and speed in areas of clear water. However, with oil and gas operations increasingly getting deeper and more remote, there may be instances where divers are not available or their safety can be at risk (for example due to pressure limits or unsafe working conditions i.e. in confined spaces). Under these circumstances, many operators are opting to utilise remotely operated vehicles (ROV) and other technologies instead.
ROVs are unoccupied, highly-maneuverable, underwater robots that are connected to a ship via a group of cables. These cables transmit command and control signals between the operator and the ROV, allowing remote navigation of the vehicle.
ROVs can range in size from that of a small computer to as large as a small truck or bigger, and typically comprise a still and video camera, lights, sonar systems, underwater thrusters, and an articulating arm (used for retrieving small objects, cutting lines, or attaching lifting hooks to larger objects).
They allow oil and gas operators to investigate areas that are too deep for humans to safely dive themselves and can stay underwater for periods longer than human divers, expanding the time available for inspection.
Autonomous underwater vehicles (AUV) are taking it a step further, not requiring operator intervention. When a mission is complete, the AUV will return to a pre-programmed location where the data can subsequently be downloaded and processed.
In October 2019, Equinor announced it had awarded a contract involving the use of a wireless underwater intervention drone and an ROV to aid with maintenance, repair or replacement work at its Njord licence. Equinor will be the first user of the technology which is expected to commence operation when the Njord field resumes production this year.
Anders Opedal, executive vice president, Technology, Projects and Drilling said it is the first contract which has been signed for the use of advanced wireless drone services in the oil and gas industry.
“We are pleased to secure a contract that will bring subsea technology a big step forward. Equinor aims to help shape the development of this type of technology, which this contract underscores.”
The underwater intervention drone (Hydrone-R) can be autonomous below Njord for months between scheduled maintenance, whereas the all-electric work class ROV (Hydrone-W) will be connected to the platform like a traditional ROV.
Both are electric and can be operated without a surface vessel, helping to reduce carbon emissions. In addition, the response time will be reduced and the operations will not be dependent on weather conditions.
“It is very exciting to be a pioneer for this type of technology offshore. Enabling personnel to plan and perform operations from shore rather than being flown offshore, this pathbreaking technology will also reduce costs,” said Olav A. Godø, operations manager, Njord.
Equinor is also doing other impressive things in the space of subsea inspections, maintenance and repair. For example, at the Åsgard field in the Norwegian Sea, the company is piloting an underwater intervention vehicle with a snake-like body and underwater thrusters that can swim around subsea installations. The robot is designed to live permanently underwater and conduct subsea inspection, maintenance and repair tasks that would typically require a remote-controlled robot from the surface.
Its slender and flexible body allows for precision hovering and manoeuvring (even in strong ocean currents), and allows it to carry out operations in confined spaces not accessible by conventional underwater vehicles.
“The vehicle can access places previous machines could not reach and is a cost-effective way to conduct maintenance and inspection. With the snake robots lying ready on the seabed, it is easier to send them to a pipeline than to send a remote-controlled robot down from the surface,” Equinor says.
Another of Equinor’s assets, the semi-submersible Kristin platform, needs to be inspected several times a year for the growth of vegetation (algae, shells and mussels) that threaten to block the seawater intakes on the platform’s fire extinguishing system. Previously, a ship was needed to perform these seawater intake inspections at a significant cost, but the use of a drone is saving the company large sums of money.
The drone can be launched without ROV operators or divers and can go to a depth of 150 metres. It is operated via a cable for control signals and transmission of HD images. Once back on the platform, the pictures can be shared with anyone who has internet access.
