BP’s 1st foray into unmanned over-the-horizon operations, using Sonardyne technology and an unmanned surface vessel, is helping it gather strategic data. It’s also a key step towards a more marine autonomous systems-led future. Craig Allinson, Survey and Positioning Lead at BP North Sea, explains.
“Throughout the life of a field, reservoir management strategies can change and, when they do, we need data to verify what impact we’re having. For the Machar field in the North Sea we changed our reservoir water injection strategy and we wanted to monitor its impact.”
“Specifically, we wanted an efficient way to keep a close eye on any seabed deformation in the field. Having considered unmanned operations for some time, we decided, in a 1st for BP, to use seafloor sensors combined with an unmanned surface vessel (USV), operated over the horizon, for data harvesting. We chose XOCEAN’s XO-450 USV, fitted with a Sonardyne HPT 3000 Mini-Ranger 2 6G Ultra-Short BaseLine system. The Mini-Ranger 2 has modem functionality, so it can communicate with and retrieve data from the Fetch subsea sensor logging nodes, also from Sonardyne, that were chosen for our seabed monitoring.”
Using a USV for unmanned monitoring
The XO-450 is an International Marine Organisation compliant, 4.5 m-long USV with a hybrid power system, including a diesel generator and solar panels, powering lithium-ion batteries to drive the electric thrusters and all instrumentation. The vessel has an 18-day endurance capability with communications (incl. dual redundant satellite communications systems), cameras (incl. thermal imaging) and navigation lights. It’s able to communicate real time with XOCEAN’s onshore control room, where pilots enable 24/7 remote, over-the-horizon control. The pilots have a full view of all the systems and can take control at any time. So we can use the vessel almost anywhere. With it, BP can go out in to the North Sea and harvest data without sending people offshore and therefore removing risk.
Fetch subsea sensors
Sonardyne’s Fetch are low-power, long-life sensors used to measure seabed deformation. This means they can continuously monitor and log the seabed depth where they are deployed, so when we retrieve their data we’re able to calculate any seabed movement, over a period of up to 10 years. We installed four Fetch sensors over the Machar field in November 2018. After a few months, BP wanted to go out and harvest the data they had collected during that time.
In early April, the XO-450 was brought by trailer to Peterhead, Scotland, where it was launched from a slipway. The USV used way points to safely transit 120 miles out to Machar, avoiding other marine traffic and installations along the 40 hour transit. During the entire transit we were able to view real-time images from the USV, BP crews could monitor it and other nearby vessels on AIS (Automatic Information System) and the onshore pilots were ready to steer around any obstacles, if necessary.
Once on site, one by one, crews located and then started communicating with the Fetch sensors, first to check their health and then to download their data, while the USV held its position, auto-piloting in a 25-30 m radius while the Mini-Ranger 2 HPT 3000 did its work, gathering about 750 pages of data from each sensor. Even with the vessel travelling at 4 knots, the noise from the vessel’s thrusters didn’t disturb the data download.
After each download, the USV’s satellite communications sent the data to shore, where BP was able to confirm, in real-time, that they had the data we needed before moving on to the next Fetch seabed unit. Throughout these operations Sonardyne specialists were on hand (remotely) with full access to the XOCEAN real-time data to ensure the harvesting was successful and completed efficiently. When the operation was complete, the vessel transited safely back to Peterhead for demobilization.
No project is that smooth of course. BP had to wait for a suitable 5-day working weather window for the operation and, after three weeks, the weather improved during Ocean Business in Southampton where XOCEAN had its XO-450 on show. With only a few hours’ notice, XOCEAN were able to drive the vessel up to Peterhead for mobilization within 24 hours.
Once offshore, there was a light well intervention (LWI) vessel operating close to one of the sensors, which meant we had to negotiate going into their 500 m exclusion zone and perform simultaneous operations. There was also a concern that the acoustics being used from the LWI vessel and ours – which were using the same frequency - could interfere with each other. So, BP took a risk-based approach and started our data collection campaign from the Fetch that was furthest from the LWI vessel, keeping in continuous contact with its crew. There was no interference at the first two Fetch units, so crews moved to the third.
At the third sensor some issues unrelated to the SIMOPs were encountered, so BP decided to move to the final sensor, closest to the LWI vessel, during daylight hours and got within 100 m of it to successfully harvest the data without any problems; a SIMOPS success.
Reducing HSE and emissions
A key reason for BP using a USV over-the-horizon, was to eliminate health, safety and environmental risk. Unmanned operations with a small vessel enable that. They achieve a significant reduction in carbon emissions – compared with a manned vessel – and total elimination of the need for humans offshore for this type of work. BP also gets a significant cost saving, compared with using a conventional vessel.
BP has been pleased with the result of this operation and we have proven the concept of data harvesting with USV. The data from the first harvest is in, on which Sonardyne has done a detailed analysis and processing, and the results are currently being assessed. The Fetch units are continuing to monitor the seabed at Machar. Their power levels mean they will be able to keep working for 10 years, which will enable BP to continue monitoring the seabed, harvesting data twice a year, using the USV, for some years to come.