The challenge

As they reach the end of their productive life, oil and gas well heads still need to be monitored whilst suspended – for up to five years, before they become fully abandoned / decommissioned. A regime must be in place to monitor the assets ‘in perpetuity’ to meet government regulations. As this is ‘abandonment expenditure’, rather than capital expenditure, any monitoring schedule must be conducted as cost effectively as possible.

Dana Petroleum (Netherlands) was faced with one such challenge in early 2023 when they needed to plan and implement a well annulus monitoring schedule for suspended wells at their Van Ghent and Van Nes subsea wells, situated in the North Sea approximately 60km West of The Hague. The wells were situated alongside others still in operation and although the topside platform remained, communication links with the sensors on the suspended subsea wells had been lost. There was an additional challenge of the system needing to be in place within 12 weeks.

The solution

The ’simple’ solution would have been to lay new communication cables from the suspended well heads to the topside platform to enable the monitoring. But this would have been lengthy, expensive and carbon intensive, involving bringing in large vessels to lay long stretches of subsea cables. A quicker, cost effective and lower carbon solution was needed. Having heard about Sonardyne’s experience and expertise in long-term subsea asset monitoring, Dana Petroleum approached us for a solution.

We have many years’ experience in providing subsea pressure and temperature data directly from well downhole gauges, mostly during the appraisal phase in a field development, providing essential data to the reservoir engineers before connection is made to the offshore or onshore facility.

Although Dana Petroleum’s requirement was well within our capabilities, there were some initial unknowns such as; field layout, pressure gauge model and manufacturer and how the equipment would be mounted to the subsea manifold. Also, which topside would be most suitable for data harvest? Something which is typically dictated by the vessel size, noise profile and water depth. The timeframe was also very challenging.

In the following weeks, Dana Petroleum provided information on the field layout, drawings of the subsea infrastructure and a strong specification for a system capable of monitoring the annulus pressures at both locations. Having received this, we were able to provide illustrations of previously designed bracketry, 3D CAD images of our potential offering and expert advice to work out the optimum placement to enable best line of site for data harvesting. With a firm specification and known time constraints we looked to our off-the-shelf products with a view to creating a semi-custom solution with our projects team.

The obvious choice was to make custom alterations to our Autonomous monitoring transponder (AMT). The AMT has been used in a wide variety of different applications including overburden monitoring and pipeline movement monitoring, all utilising and autonomously logging pressure sensor data. These solutions can operate autonomously over long periods of time, over five years – depending on deployment – logging data and making it accessible for wireless upload.

The topside platform of choice was a Nano topside equipped with a ruggedised laptop running Sonardyne’s Monitor software fitted to a small crew transfer vessel that would pass by the wells at regular intervals, delivering workers to the platforms. The size of the vessel dictated a small portable solution but other options are available for all sizes of vessels.

Once the seabed and topside products were selected, custom modifications were made by the projects team to the AMT, allowing the pressure sensor to be connected to the annulus via a flange – rather than inside the AMT –to give flexibility in the location of the AMT and achieve best line of communication with the Nano transceiver when it passed overhead.

A factory acceptance test was witnessed by Dana Petroleum where our projects team provided documentation and coordinated the testing. Following this the equipment was shipped and ready for installation – all within a few months!

The challenge

Without surface platforms, acoustic data from the subsea sensors had to be harvested by crewed vessels in the early years of the field’s operation. This was costly, carbon heavy and posed a risk to personnel in often challenging sea conditions.

With a company ‘Powering Progress’ strategy to achieve net-zero emissions by 2050, Shell was looking for an alternative data harvest method that would reduce cost and risk as well as its carbon footprint.

The solution

Marine robotic platforms provide the opportunity to remove carbon and personnel risk. Working with the customer and XOCEAN as a sub-contractor we developed a solution that would save time, costs. and carbon, while also eliminating the human risk element, using a USV to conduct the data harvest.

The proposal was to use our HPT 3000 transceiver mounted to an XOCEAN USV to remotely harvest data from the 75 seabed PMTs. The HPT 3000 is perfect in terms of size, weight and power for deployment from a USV and can communicate with seabed transponders at depths up to 995 m (or 4000 m with an extended range version).

XOCEAN USVs are perfect for the data harvesting mission at Ormen Lange. They enable full over-the-horizon 24/7 operations. This means that operators and data analysts can remain safely onshore whilst the operation takes place and data can be sent ashore and verified in near real-time using the USV’s satellite communications.

This satisfied Shell’s commitment to accelerate the transition of their business to net-zero emissions and to integrate sustainability within their business strategy. Following the successful PMT installation in 2019, a five year project was agreed where Sonardyne are responsible for the data delivery to Shell and XOCEAN are responsible for delivering the transceiver to the field for data collection via their USV.

The results

The project began in January 2020 and this was the first time a remote USV data harvest was completed offshore in Norwegian waters by any operator.

Whilst the USV and HPT 3000 were in Norwegian waters surveying the Ormen Lange site, the Sonardyne and XOCEAN personnel never left their bases in England and Ireland.

The data harvest was monitored in real time, 24/7 and the two teams were in contact with each other as well as the remote equipment. This mean that data was being monitored by our team as it was collected and there was no risk of the USV returning with missing or irrelevant data. Had there been any missed or partially collected data the Sonardyne team could ask the XOCEAN team to return to recollect from a particular PMT whilst still in the field, rather than waiting until the vessel returned and having to send it out again.

Successful data harvests have been conducted yearly since 2020 and continue to be a cost effective, low impact operation. This year we collected data from the Ormen Lange site twice, in Spring and Autumn.

If you think you have a similar challenge for us, contact us today.

With several decades of subsea transponder and release manufacturing experience, Sonardyne was an obvious choice for a solution.

Our RT 6 family of acoustic release transponders combine the extensive track record of our previous models with the flexibility of a 6G hardware platform, meaning they can be deployed, located and released using any of our Ranger 2 USBL systems or 6G topsides.

An acoustic release transponder is fixed to a subsea asset so it can be found and recovered. An acoustic signal from a surface vessel locates the transponder on the asset. A second acoustic signal then tells the transponder to release the mechanism anchoring the asset to the seabed so that it can be retrieved.

Having gained a full understanding of Allton’s requirements, our engineering team worked closely with them to custom modify an existing RT 6 model to meet their exact needs. Aleksander Kristiansen, Supply Chain and Asset Manager, from Allton explains, “The custom manufacture of our RT 6-4000 was based on an existing model (RT 6-1000) which Sonardyne modified to suit our operational needs. This included extending its range and adding a secondary burn release circuit.

Working with our customers to fully appreciate their needs and the challenges their businesses face enables us to develop solutions for their specific operations. As Trevor Barnes, Sonardyne Sales Manager, explains: “Allton was looking for a robust, reliable acoustic release to give them confidence in retrieving their equipment from a range of depths. Whilst our RT 6-1000 is perfect for depths of up to 1,000 m, Allton operate in depths of up to 3,500 m so our engineers worked closely with them to develop an RT 6-4000 to enable this. A secondary burn-wire release was also added at their request, as a backup in the unlikely event that the first acoustic release fails.”

Aleksander Kristiansen continued “Sonardyne were always willing to assist and put the right technical expertise onto the variety and wide range of tasks to solve our many, often complex at times, challenges. Their creative ideas were well aligned with our expectations and letting us borrow equipment for an extensive time to conduct in-house testing was much appreciated. It gave us further confirmation that we were making the right choice in the RT 6 releases.”

Allton’s nodes are now fitted with RT 6-4000 acoustic releases to ensure that they can be reliably located and retrieved from the seabed at all their operating depths and in any conditions.

They can now provide data across all of their services with confidence that they have consistent, reliable access to their network of nodes.

Our standard RT 6s come in three depth ratings, 1,000 m, 3,000 m and 6,000 m and all use our workhorse Ranger 2 USBL system or deck topside to command and track. Some models can even be controlled using an Android app.

If you have a similar operational challenge, take the worry out of mooring and retrieving your kit and talk to us today.

“Historically, smaller electric vehicles have been limited in the amount of work they are capable of due to size, power and operational limits presented by weather conditions and surroundings.

Recent iterations of handheld ROVs such as the VideoRay Defender have looked to change what electric ROVs are capable of, while maintaining a platform that is easy to mobilise, operate and maintain. That said, the ROV is only as powerful as the tooling that it holds, so it still requires support from companies such as Sonardyne, to reduce the form factor and weight of their tools and sensors, to enable their integration and deployment offshore.

Atlantas Marine have already been utilising the SPRINT Nav Mini to great success on our Ocean Modules V8 M500 platform, but the latest SPRINT-Nav U will allow us to go further and integrate it onto our VideoRay Defender ROVs, and provide another service that we can offer our customers – a hand-launched ROV, that can be mobilised in as little as half an hour, transported to site in the back of an car” Mark Salter, Senior Project Manager, Atlantas Marine.

“Like the other hybrid navigators in the SPRINT-Nav family, SPRINT-Nav U’s true north seeking gyrocompass means that it delivers reliable subsea navigation even when in close contact with the types of environmental factors outlined above. With its ultra-compact form factor (135mm X 114mm) and a weight in water of just 0.6kg, SPRINT-Nav U gives unrivalled navigation capability to small marine robotic system allowing users to maintain a heading accuracy of 0.15° regardless of environmental factors.

“SPRINT-Nav U has been designed with our customers in mind. We’ve been speaking to them for a number of years about their aspirations for operations with small platforms. With the help of valued customers like Atlantas Marine, our trials have demonstrated a variety of use cases for this new, compact navigator and we’re excited to work on many more innovative uses in future.” Aidan Thorn, Business Development Manager – Marine Robotics, Sonardyne.

Small, light, precise

SPRINT-Nav U is simple to integrate into any marine vehicle along with other payload sensors and uses same field-proven web user interface found on the SPRINT-Nav Mini. Pre-calibration in the factory also means that SPRINT-Nav U is incredibly quick to set up and deploy on site with an alignment time of as little as five minutes, compared to the standard 15-20 minutes of other gyrocompassing inertial navigation systems, making it the world’s fastest aligning hybrid navigator.

“SPRINT-Nav U can turn any marine robot into a survey grade platform. For UXO and asset inspection it drastically improves deliverable data quality. As part of the proven Sonardyne SPRINT-Nav family, customers can be assured of reliable, accurate navigation and positioning every time, no matter the operating environment.” John Houlder, Senior Product Manager, Sonardyne.

What the customers thought

Mark Salter, Senior Project Manager at Atlantas Marine – “Of particular significance to us, is the work we undertake on offshore wind turbines. With a high AC voltage running through the subsea cabling, and the strong magnetic signatures associated with that, plus the ferrous nature of the turbines themselves, the SPRINT-Nav U allows us to offer our customers a level of accuracy and precision that was previously not possible. It allows us to state with much higher confidence the location of any faults and anomalies, and allows us to repeat inspections, year on year, as we document the changing condition of those faults. With the positioning and control managed through Greensea, we can set up autonomous routes and sea patterns with more accuracy and precision than even before, especially in the environments we most commonly find ourselves.”

Richard Stanley, Project Leader at Atlantas Marine – “Providing improved accuracy when operating in ports and areas where large metallic objects are buried on or beneath the seabed, improves not only the reciprocal bearings of the lanes the ROV is flying, but feeds a more accurate heading into the navigation solution which is streamed to the surveyor. Beyond seabed surveys, the ability to maintain a stable heading while piloting a compact inspection-class ROV through culverts with rebar or complex subterranean tunnels is a key advantage. It reduces the need for frequent heading corrections and ensures precise navigation when traversing long distances. This ultimately enhances the quality of deliverables for our clients, providing us with a competitive edge when deploying our equipment.”