Underwater drones have the potential to reduce costs, mitigate risk, improve efficiency and cut CO2 emissions from offshore oil and gas operations
Oil and gas companies have just begun to scratch the surface when it comes to deploying underwater drones or remotely operated vehicles (ROVs) that are permanently or semi-permanently based on the seabed near an offshore installation. Advances in AI, sensors, video, robotics, batteries, and connectivity make these offshore automatons capable of performing maintenance and repairs 24 hours a day, seven days a week in all types of weather without the need of an OSV.
As a result, these resident robots have the potential to reduce cost, increase safety by mitigating the risk to crew and improve efficiency and operability.
In October, Norwegian oil and gas company Equinor signed a 10-year subsea services contract worth €40M (US$44M) with Italy’s Saipem to use undersea resident robots to support the Njord field development on the Norwegian Continental Shelf (NCS).
Commenting on the contract, Equinor chief technology officer Sophie Hildebrand says: “We have absolutely stepped into the future. I think it is only up to our imaginations as to what we can do with this technology.”
Under the contract, which contains a 10-year option, Saipem-Sonsub will deploy its underwater intervention drone (UID) Hydrone-R starting in Q1 2020 and the all-electric work-class ROV Hydrone-W in 2021.
“This is a historic contract in the oil and gas industry,” says Equinor executive vice president, technology, projects and drilling Anders Opedal. “It is the first contract signed for the use of advanced wireless drone services.” Mr Opedal says that the contract “will bring subsea technology a big step forward.”
The drone may be autonomous below Njord for months between scheduled maintenance, whereas Hydrone-W will be connected to the platform like a traditional ROV. Both are electric and can be operated without a support vessel.
Since a support vessel is not needed, using resident robot technology will help Equinor advance its goal of reducing its CO2 emissions from its operations. It plans to reduce carbon emissions by 50% from its logistics supply chain by 2030 based on its 2011 levels. Since 2011, it has cut CO2 emissions from its logistical operations by a total of 600,000 tonnes.
“It is very exciting to be a pioneer for this type of technology offshore,” says Njord operations manager Olav A. Godø. “Enabling personnel to plan and perform operations from shore rather than being flown offshore: this pathbreaking technology will also reduce costs,“ says Mr Godø.
Equinor’s proprietary docking station for data transmission and subsea induction charging will be installed on the seabed near Njord and used by the underwater drone.
According to Saipem, the Hydrone-R as a subsea resident drone can remain underwater for 12 months, has wireless operability and can be connected to subsea infrastructures via through-water communication links. The drone can cover an area within a 10-km radius for inspections and interventions. Even larger distances can be covered with intermediate subsea docking stations for recharging, mission download or data upload, providing a flexible range of operations.
Hydrone-R can also operate more traditionally, launched subsea and then being retrieved on the surface upon completion of its mission.
First steps towards resident robots
Equinor, then Statoil, took its first steps towards introducing resident robots in 2016 when it awarded a 10-year contract to Norway’s IKM Subsea AS for ROV and subsea services for the Visund and Snorre B fields in the North Sea.
Under the Nrk750M (US$82M) contract, which contains a 15-year option, IKM Subsea introduced the resident ROV (RROV) concept, a permanently subsea-installed ROV system operated from a dedicated operational base onshore. The contract has allowed IKM Subsea to take a phased approach to developing its RROV.
Under its contract with Equinor, IKM Subsea operates four ROVs on the Snorre B and Visund installations in the North Sea. They can all be operated from the Onshore Control Center at Bryne, Norway, which is manned 24 hours a day, 365 days a year. One of these four ROVs is the Merlin UCV RROV, which can stay submerged for up to three months; it operates on a 1,000 m excursion capable tether management system from a subsea garage, which is connected to a host platform.
For all their benefits, subsea resident robots still pose a number of technological challenges, from remote control functionality to reducing maintenance requirements.
“A key requirement has been station keeping, to help with certain tasks when you need the ROV to be stationary,” says IKM Subsea’s engineering manager Ments Tore Møller.
The RROV employs UK acoustic and non-acoustic technology firm Sonardyne’s Sprint-Nav hybrid navigation instrument. Sprint-Nav is built around Honeywell ring laser gyro inertial sensors, in an inertial measurement unit (IMU), coupled with Sonardyne’s Syrinx Doppler velocity log, and a high-precision pressure sensor. Tightly integrating raw data from these sensors at a low level means higher levels of accuracy and reliability are achieved, according to Sonardyne. It says the technology allows ROVs to calculate their own position for longer periods of time with less drift.
Tethered ROVs, of course, also have their limitations. Survey work, for example, is limited by the length of the tether. Without a tether, and aided by Sprint-Nav, a vehicle can travel further between nodes where it can be recharged or transfer data at a docking station.
Live remote-controlled operations of the resident robot are facilitated by Sonardyne’s BlueComm free space optical modem, which provides live video transmission through the water.
Another option for resident robots involves deploying a cage with battery packs to allow for independent operation from a support vessel. The cage creates allows communications and control of the resident robot from onshore via a surface buoy and 4G cellular network, says Mr Møller.
To further support RROV operations, IKM Subsea is also considering creating a digital twin – a virtual replica of the real world. To recreate the subsea environment, Sprint-Nav would use positioning data in conjunction with a 3D sonar. If the ROV’s communications link or the sonar dropped out, Sprint-Nav could continue calculating the vehicle’s position. A digital twin would also make it possible to simulate procedures, conduct more realistic training and reduce time on the real system, says Mr Møller.