Using a hammer to crack a nut? Try using a USV instead

USVs are no longer new. They’ve been used in defence for some time now, for a range of tasks from surveillance to mine counter measures. USVs are being used to survey coastal and offshore waters in hydrographic surveys, for ocean science and in oil and gas

The challenge

Crewed vessels used in offshore construction projects are costly and can even hinder progress. But it doesn’t have to be that way. Other sectors that operate in the marine space are now finding new, smaller, smarter, cleaner tools. They’ve been using uncrewed surface vessels (USVs), so the big, crewed vessels can stick to the jobs they’re good at.

So why are we not using them heavily in offshore construction?

One reason may be because offshore construction was in fact an early adopter. But, at the time, there were only a handful of commercial USV operators whose vehicles were just too big for what was needed, making them unwieldy to deploy from an offshore vessel, defeating the point of the exercise.

Another may be the worry of the complexity involved in offshore construction. Creating complex structures on shore is one thing. Creating them under metres of salt water is entirely another.

Then there is the issue of communication and control over the construction process. Making sure each step is taken exactly as planned is fundamental to the overall success of a construction project.

The solution

USV technology has come a long way since their inception. They’ve been used in defence for some time now, for a range of tasks from surveillance to mine countermeasures. USVs are being used to survey coastal and offshore waters in hydrographic surveys, for ocean science and in oil and gas. They’re being used to go out and gather data, either as a platform for oceanographic instruments or by carrying acoustic communications systems to harvest data from sensors deployed at the seabed. You could think of them being like a remote-controlled Dunker.

USVs are now part of the toolbox across a number of sectors and the levels of sophistication and capability are increasing. Worries about lack of control, the complexity of operations or large clunky kit that isn’t up to the delicate tasks required in offshore construction are today unfounded.

In offshore renewables and oil and gas USVs are being used as part of site and seismic surveys, and then through field life, for inspection operations. They’re also being used for maintenance and repair, by acting as deployment platforms for autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs) and even aerial drones (UAVs).

The results

Today there’s a wide choice of USVs to choose from. From one-man portable USVs to full sized vessels, and on to fully electric coastal systems and hybrid long-range ocean-going vehicles that can operate for weeks on end. The range of commercial models has also grown. You can buy them outright or purchase a data service where you just order the end result – be it data or an inspection campaign.

USVs can now play a central role in construction operations. They can streamline operations and reduce risk for manned offshore construction teams. When deployed they reduce reliance on heavier, costlier tools and free-up crewed assets to be used on elements of a project where they’ll bring more value.

How to optimise carbon storage monitoring with marine robotics

For a long time, while carbon capture and storage (CCS) in offshore underground reservoirs had been widely regarded as a major way to reduce carbon emissions, it failed to attract the up-front investment needed to make it work. That’s now changing.

The challenge

In today’s far more climate conscious world, sentiment and interest in CCS has very much changed. Significant projects are now being planned. Projects are moving forward in Norway, Netherlands and the UK. Carbon storage licenses are being awarded and wells are being drilled specifically for carbon capture and storage.

Since 1996, CCS projects have been relatively small, yet their potential is vast. On the UK Continental Shelf alone there’s at least 78 gigatonnes of CO2 potential storage capacity – some 200 times the UK’s 2016 emissions*.

From capture to transport by pipeline and injection into a suitable geological formation offshore, there’s a lot to process. But the challenges do not end there. What happens to the CO2 once injected? How will we know if it finds a leak path to the surface?

To answer these challenges and achieve the visions that operators from Equinor in Norway to BP in the UK are promoting, increased capability for marine robotics is required.

The solution

Thanks to the Energy Technologies Institute (ETI) funded three-year research programme back in 2014, this challenge for increased capability of marine robotics has been attained. The project was delivered by a consortium of experienced companies including Fugro, National Oceanography Centre (NOC), British Geological Survey (BGS), Plymouth Marine Laboratory (PML) and ourselves, Sonardyne.

Along with increasing the capability of marine robotics for successful CO2 storage, four key technology elements for large carbon storage and monitoring projects were identified.

The first is a low-power and hence long-endurance autonomous underwater vehicle (AUV). This is required for cost-effective wide-area coverage surveys during baseline and repeat environmental surveys. We found using a combination of our Solstice side scan sonar and chemical sensing worked extremely well.

Second and third elements are seabed landers capable of detecting and monitoring any leakage at high-risk locations. These consist of two different landers, one using an active sonar and the second combining passive sonar and chemical sensing.

The active sonar lander, based on our Sentry integrity monitoring system (IMS), gives sensitive and reliable automated leak detection capability across a wide area. For instance, around an injection well, Sentry can monitor an area of over 2.3 million square metres, to help visualise that’s equivalent to around 325 football pitches. The passive sonar and chemical lander, uses the smarts from our underwater acoustics capabilities. It’s capable of both detection of leaks, but offers improved verification and has the potential to estimate leak rates at shorter ranges.

The fourth and final element is a surface gateway to enable communication between a shore-based monitoring office and the underwater systems. Such a gateway can be deployed from a fixed platform, from a moored buoy or from an uncrewed surface vessel (USV), many variants of which are now readily available in the market for over-the-horizon data harvesting missions.

We have a range of payloads suited specifically for use on operator’s USVs for their requirements. We also offer our own end-to-end data-harvesting service, when you just want the data without the worry about the interfaces involved in getting it.

Our system of systems approach to CCS was tested on the ETI project. Wideband acoustic communications between the underwater landers and a buoy on the surface was used to forward all data via satellite communications to a server. This type of set-up is well-proven and used globally on tsunami monitoring systems. Display and interpretation of the monitoring data can be simply integrated into a third-party system to allow non-expert users access via a web portal. From here they can see data visualizations and run reports.

The leak target was deployed in the North Sea, east of Bridlington. The NOC’s Autosub Long Range (ALR) was deployed from the small port at Bridlington and towed a short distance off the coast. After the ALR performed a series of tests to demonstrate safe navigation, the leak – a small CO2 leak – was turned ‘on’ with a flow rate of between 16 and 20 litres per minute of gas at depth, depending on the state of the tide.

With the leak “on”, ALR performed a series of different wide-area and fine-area search patterns over five days to seek out the leak. The sensor hub on the vehicle processed in real-time a complex set of Solstice sonar, physical and chemical sensor data, into useful information.

Automatic target recognition algorithms were used to identify any leaks or regions of interest. The system then scored these regions of interest and saved a small “snippet” of the sonar image data. At regular intervals throughout the survey, ALR would surface and send back data via satellite, including navigation data, chemical and physical sensor data and details of snippets of sonar data from detected leaks – an example of which can be seen below.

All of the uploaded data was simultaneously transferred to an internet server which allowed for presentation and interpretation using Fugro’s Metis software. This is an intuitive data delivery platform that allows metocean, vehicle navigation, chemical and sonar snippet data to be combined and displayed. This allowed data sharing across a wide team and supported operational decision making.

During the five days of testing, the ALR travelled a total of 270 km and could have surveyed 54 sq km of seabed in normal operation. However, for the purposes of the demonstration, a total of 16.1 sq km was actually surveyed. Throughout its mission, the ALR was remotely controlled from the shore, mostly from the NOC’s control room in Southampton.

The results

The ETI project consortium demonstrated a functional “system of systems” which can provide operators of offshore CO2 storage sites with a high level of confidence in their safe operation and assist in the provision of regulatory compliance.

We’ve proven it is possible to conduct shore-to-field-to-shore environmental survey operations using a long-endurance AUV. We’ve also shown it’s more than possible to operate well in excess of normal AUV deployments.

This method of working makes it possible to rely on a small local deployment team for CCS projects. The small team can then be supported by remote shore-based operations and a data interpretation team. This cuts both the time and cost of CCS operations considerably.

It is also entirely possible, and has been demonstrated elsewhere, that a further reduction of human decision making can be achieved to reduce operator intervention.

The ETI project demonstrated that it is possible to build highly cost-effective and autonomous sensing systems with on-board intelligence. These systems are both simple to deploy and operate and are very cost competitive with vessel-based or vessel supported AUV survey operations.

The project members have also developed two flexible seabed lander packages capable of extended duration deployments of six months to a year. These can provide localised and still also wide-area monitoring, automated processing of data subsea and communication of that information to surface.

Looking beyond carbon capture, the potential applications of such integrated marine robotic and intelligent remote sensing technologies are many and varied across ocean science, renewables, security and naval domains.

Unlocking the Gulf Loop Current

The Gulf of Mexico is home to one of the world’s most energetic oceanographic phenomena – the Gulf of Mexico Loop Current. Reaching intensities of between 2 – 4 knots and measurable down to 1,000 m, the Loop Current System (LCS) also regularly sheds Loop Current Eddies (LCE).

The challenge

LCEs are highly energetic anticyclonic (clockwise) rotating rings of warm water, roughly 300 km across and 500 – 1,000 m deep, with current speeds of up to 4 knots. These break away from the extended Loop Current about every 8-9 months and slowly drift west-southwestward towards Texas or Mexico at about 3-5 km per day.

When an LCE forms at the height of hurricane season, it has the potential to fuel rapid intensification of hurricanes. This is what happened in 2005, just before Hurricane Katrina passed over and “bombed” into a Category 5 hurricane.

Warm circulating eddies can break off the LCS into the western, northern and central Gulf. These eddies are so highly energetic that they regularly disrupt oil and gas operations. But, they’re also critical to the Gulf of Mexico’s oceanographic system, including its nutrient and food cycles and, most importantly, hurricane intensity.

Despite 50 years of effort by the scientific community to understand the processes underlying the LCS, its behaviour remains unpredictable. To some extent, this is because of interactions with the deep eddies, which have been difficult to track from measurements near the sea surface. For this reason, a multi-year scientific study has been launched, led by the University of Rhode Island(URI). It includes a major deployment of Sonardyne’s Pressure Inverted Echo Sounders(PIES).

The solution

Following a recommendation by the US National Academies of Sciences, Engineering, and Medicine a long-term, US$ multi-million research program to plug the gaps in understanding and predicting the LCS is now underway.

The initial two-year project comprises an array of 15 URI CPIES, five Sonardyne CPIES and five Bureau of Ocean Management PIES. These are in an array, spaced 60 km apart, at depths down to 3,500 m in the area of the extended LCS. Initially deployed in June 2018, for a nominal two-year study, the units are fitted with batteries that can keep them powered for up to 36 months. This will allow for data gathering continuity in the event of a subsequent expansion of the program.

A core element of this scientific study is the array of seabed-mounted sensors, including Sonardyne’s PIES. PIES were originally developed for the marine seismic industry to measure average sound velocity in the water column. They do this by transmitting a wideband acoustic pulse from their position on the seabed. This pulse is reflected off the sea surface and returns to the seabed where it is detected by the PIES.

Oceanographers, however, use PIES differently. Their goal is to derive important physical data, including the strength and direction of currents. This is based on the principle that there’s a strong correlation between two-way travel time (usually known as tau) and vertical profiles of temperature, salinity and density. As a consequence, where this profile has been derived from historical data, an empirical relationship can be derived, which enables the density profile to be inferred from tau.

At a basic level, a laterally separated pair of PIES will, therefore, provide a vertical profile of velocity, and by deploying an array of PIES, local horizontal velocity and density fields can be mapped over the period of deployment.

URI has pioneered and refined the use of PIES for this purpose. While URI has a long history of developing its own PIES instruments, it decided to use Sonardyne’s PIES, as well as its own. This was primarily because a comparison study off the coast of Oregon* indicated that the Sonardyne PIES could generate similar accuracy data efficiently, potentially enabling longer deployments – and because of their telemetry capability.

Sonardyne’s integrated high-speed (up to 9,000 bps) acoustic telemetry capability also enables remote reconfiguration of the instruments and wireless retrieval of data to surface vessels, without interrupting the bottom pressure record.

These capabilities are based on Sonardyne’s extensive expertise in underwater acoustics, signal processing, hardware design and custom engineering, which URI recognises, have the potential to reinforce future PIES development.

Sonardyne’s expertise was central to reconfiguring a standard PIES as a CPIES (Current PIES) which was needed for this project to allow for near-seabed current data to be harvested alongside the PIES pressure and tau measurements. It also delivers important data on deep eddy currents above the seabed/water interface.

The reconfiguration involved connecting an Aanderaa Doppler current sensor to the PIES, which then served as a battery pack and data logger for the current sensor, deployed 50 m above the PIES on a float. Combining the deep current observations with the deep pressure observations enable data from the array to be referred to a common reference surface.

The results

An interim data retrieval campaign, using acoustic telemetry, was successfully completed in September. While the principal purpose of this was to recover an initial three-month-long data set, one notable feature found in the data was echoes, thought to be from fish, shrimp or squid.

This has been seen in other studies carried out by URI. We believe it is related to the transport of nutrients by deep currents crossing from the deeper to shallower thermocline side around the periphery of the Loop Current or a passing LCE.

The present array will inform planning for a longer-term, 10-year campaign. This could see a substantially expanded array of PIES deployed into Cuban, as well as Mexican and US waters. The aim of this larger array would be to provide near real-time data as input for LCS forecasting models.

Loop Current and LCE forecasts have the potential to benefit a wide range of users, from oil and gas operations and hurricane forecasters to fishing and tourism. Furthermore, improving ocean modelling in the Gulf of Mexico has the potential to provide a standard for improving prediction efforts in other ocean basins also.

Trendsetter Vulcan Offshore uses a SMART solution to monitoring wellhead fatigue

The challenge

An operator wanted to cost-effectively drill a subsea side-track on an existing subsea well to increase reservoir recovery to a floating production facility in 150 m water depth.

That meant drilling from the existing well bore. However, there were concerns that the remaining fatigue life of the existing wellhead would be quickly consumed under the load and strain imposed by the physical size of the current generation of blowout preventers (BOPs) operating from a semisubmersible drilling rig.

A system was required that would significantly reduce the fatigue loading on the wellhead during the drilling operation.

The solution

Houston-headquartered engineering specialist Trendsetter Vulcan Offshore (TVO) provided and deployed its tethered BOP Wellhead Fatigue Mitigation System. Key to the system is our Subsea Monitoring, Analysis and Reporting Technology (SMART) and our Dunker 6 telemetry transceiver deployed temporarily from the vessel for the project.

TVO’s system alleviates the impact of a larger BOP on wellheads by arresting the motion of the BOP stack via four tethers, anchored to the nearby seabed. This reduces wellhead cyclic stresses and extends fatigue life, for both mature and newer wellhead systems.

To ensure safe operation within fatigue limits of the well system, any movement of the BOP and the lower drilling riser is monitored using our SMARTs. In this case, two were installed – one on the BOP and one just above the lower marine riser package (LMRP). They were used not only to monitor the movement of the BOP and bottom of the drilling riser, but also the angle between the two.

Value adding edge analytics

The SMARTs also provided onboard data processing so that just summary packets of information (minimum, maximum and standard deviations), for both rotation and acceleration in all axes were supplied wirelessly, every 15 minutes, to the topside via the Dunker 6, which was deployed from the semi-submersible drilling rig.

Transmitting the processed data alone helps to reduce data overheads and prolong battery life. This is because less data needs to be transmitted to the topside software, which results in the information being transferred and updates performed at a fraction of the time compared to raw data transfer.

At the topside, the data was put through TVO’s fatigue analysis software, installed on Sonardyne’s topside computer for the project, which included algorithms developed by TVO to determine fatigue damage accumulation based on measured motions. The results were then transferred into a 4D Nav user interface dashboard, where the data was displayed. This meant the drilling crew were able to be constantly aware of the fatigue load on the wellhead during their drilling program.

Post drilling, the operator was able to download all the raw data gathered for in depth analysis and calculation of the wellhead’s remaining fatigue life for its future operations.

The results

Combining TVO’s experience within this domain with our broader subsea engineering, communication and positioning technology expertise provided an off-the-shelf solution that could be tailored for this application and would be equally applicable for more complex scenarios.

There is a growing need for BOP fatigue mitigation systems globally, but especially in those markets where there are mature subsea wellhead systems, and this system provides an effective and proven solution.

SMARTs are highly configurable, low-power monitoring and analysis platforms that come with internal six degrees of freedom motion sensors. Get in touch to find out how they can aid your operation.

Seismic operations in the transition zone

When seismic operations move into very shallow waters, accurately positioning seismic nodes or ocean bottom cables (OBC) on the seafloor can pose a challenge.

The challenge

The transition zone environment is often highly reverberant, the vessels used are often noisy and they can be a considerable distance from the acoustic transponders used to position the nodes. What’s more, shallow water makes nodes especially prone to movement, adding a further complication to proceedings.

Repeated node positioning operations conducted from vessels are costly and time consuming. Noisy environments can inhibit the quality of information and manned vessels are a costly option for completing work that can be done remotely.

The solution

To solve these issues, Sonardyne has created our TZ Transceiver. It’s very compact and simple to operate. Ideally suited to installation on manned workboats and USVs, it’s already being used for conducting acoustic positioning operations with seismic nodes deployed in the transition zone.

The TZ Transceiver works by collecting hundreds of acoustic ranges from transponders such as our TZ/OBC, TZ Transponder and Small Seismic Transponder 6. These are often attached either directly to the seismic node or to a deployment rope nearby. The ranges are merged with the vessel or USV’s GNSS data so that an accurate position of each node can be calculated.

Mounting our TZ Transceiver onto a USV is ideal because it can follow the mother vessel autonomously and position the nodes as they are being deployed. Alternatively, it can be tasked to perform a position verification check to ensure the nodes have not moved.

The results

Fitting a TZ Transceiver to a USV such as the installation on Maritime Robotics’  Mariner USV is a very cost-effective force multiplier. The addition of the transceiver eliminates the need for a manned vessel to conduct the same routine operations.

Weighing in at 1,900 kg, Mariner is 6 m-long, 2 m-wide. It includes a moon-pool and an elevator mechanism for sinking and lowering sensors, such as our TZ Transceiver.

The vehicle is designed for both offshore and coastal applications and can be deployed and operated from a larger manned vessel or even over the horizon from a shoreside office. This increases the productivity of the existing survey crew as well as the overall profitability of seismic operations.

Measuring Mount Etna – an underwater monitoring first

A network of Sonardyne instruments deployed by scientists from GEOMAR Helmholtz Centre for Ocean Research in Kiel for 15 months has measured underwater slippage of the southeast flank of Europe’s most active volcano, Mount Etna.

The challenge

While satellite observations have previously shown that the flank of the volcano is slowly sliding towards the sea, until the establishment of this network, it had been impossible to confirm if and how the submerged segment was moving beneath the ocean.

Results published in the international journal Science Advances confirm that the entire flank of the volcano is in gravity-driven motion and in one event the slope slipped about four centimetres in just eight days. The risk is that sudden and rapid failure of the entire slope could result in a catastrophic tsunami in the Mediterranean.

The solution

A network of five Sonardyne Autonomous Monitoring Transponders (AMTs) were deployed in April 2016 by scientists at GEOMAR and Kiel University. The placement of the transponders covered the fault line that represents the boundary between the sliding flank and the stable slope. Three AMTs were situated on the sliding sector and the final two on the side of the fault line that was presumed to be stable.

The AMTs acoustically measure the distances between each other with a millimetric precision. This sound based underwater geodetic monitoring network, so-called marine geodesy, was a first for monitoring a volcano’s movement underwater.

Geraint West, Global Business Manager – Ocean Science told us “The AMT is a highly flexible instrument that has been used by research institutes around the world to measure seabed movements as diverse as rapid canyon turbidity flows to plate motion at deep subduction zones. This project is the first time that it has been used to measure the slippage of a volcano’s submerged flank.”

“The AMT was originally developed to measure deformation of the seabed caused by the extraction of hydrocarbons over several years.” Tom Bennetts, Sonardyne Projects Manager added.

“Sonardyne first deployed AMTs on a large project over the Ormen Lange field in the Norwegian sector of the North Sea. For that project, some 220 individual instruments were deployed. The precision and endurance required for the Ormen Lange project showed us – and others – that our AMTs are also ideally suited for scientific studies of the seabed.” Bennetts clarified.

The results

The results published in the international journal Science Advances confirm that the entire flank of the volcano is in gravity-driven motion rather than the ascent of magma. One event saw the slope slip about four centimetres in just eight days. There is a very real risk that a sudden and rapid failure of the entire slope could result in a catastrophic tsunami in the Mediterranean.

Chris Hammersley, Project Engineer – Navigation Systems for Sonardyne said “Through several projects with major AMT deployments, we’ve built up a close relationship with the scientists and engineers at GEOMAR. We’re on standby to support them remotely through AMT deployment and routine data recovery missions. From our head office in the UK, we’re able to support these projects remotely, 24/7. For the Mount Etna Measurement project, we’ve been able to advise on optimal configurations for the instruments as well as troubleshoot any issues that arise, ensuring that GEOMAR have been able to use valuable ship time on site to best effect.”

The results of the study do not allow a prediction of whether and when a rapid failure of the slope might occur. For this reason, further research into the geological processes at and around Etna and other coastal volcanoes will continue. The success of our AMT deployments at Etna has secured the future use of sound-based geodetic monitoring networks for further studies.

Read more about GEOMAR’s project here.

Deepwater data analytics – asset monitoring at the edge

Thousands of kilometres of pipeline, flowline, and interconnecting spool pieces are installed on the world’s sea and ocean floors. They create vast networks and their design can be complex, having to account for a huge array of variables, from water depth to expected flow composition and behaviour.

The challenge

Sometimes, it’s not always possible to account for all of the variables that an oilfield infrastructure is subject to. This can lead to issues. External vortex induced vibration (VIV) or internal flow induced vibration (FIV), which can sometimes be caused by slugging. Slugging is created by variable or irregular flow of gas and fluids through risers, pipelines, flowlines or spool pieces.

These issues can cause problems for process equipment, impact production efficiency and, critically, accelerate pipeline fatigue. This has knock-on effects for design life. It can even cause pipelines to be displaced, entrenched or erode the supports they stand on.

When FIV occurs, pipeline engineers need all the information they can get about just how much this is happening and to what degree. This enables them to re-calculate the remaining fatigue life of the infrastructure and decide on the best remediation methods. Unfortunately, monitoring exactly what is happening – what forces the pipelines, flowlines or spool pieces are being subjected to – can be challenging, especially in deep water.

International subsea engineering company Oceaneering International Inc. was asked by an operator to solve this exact problem. They had a number of spool pieces deployed in more than 1,000 metres of water, running between riser bases and flowline termination assemblies. They were being subjected to sudden and frequent slugging movements.

These movements had already resulted in new spool piece supports having to be installed. The operator’s engineers needed to assess the resilience of the new supports and learn more about the vibration the spool pieces were encountering. The challenge was that no motion monitoring sensors had been fitted prior to commissioning. The solution would need to provide accurate and accessible data using a technique that was not cost-prohibitive to install and operate.

The solution

Oceaneering’s solution used an innovative, wireless approach with Sonardyne’s Subsea Monitoring, Analysis, and Reporting Technology (SMART) sensor as a key element of the project.

SMART sensors are, well, smart. They contain low-power MEMs-based (micro-electric mechanical systems) inertial measurement units (IMUs), subsea processing power and integrated acoustic modem capabilities. This means they can autonomously measure, log and process high-frequency, pipeline or spool piece acceleration and angular rate motion over pre-programmed monitoring intervals.

Importantly, SMARTs, which can be integrated with many different subsea sensors to suit a wide variety of applications, process data at source. This is then sent as small statistical summary packets of data – based on parameters set by the user – through the water column to a surface transceiver. This method reduces the need to send time-series, or raw, data up to the surface for analysis, which prolongs battery life, maximizes bandwidth availability and provides useful information to engineers faster. It’s edge analytics and subsea communication technology in one battery-powered autonomous compact unit. And it’s able to work on extended deployments down to 7,000 metres water depth.

For the high-frequency motion, SMARTS were installed on each spool piece at a location between the riser and flowline termination assemblies. To monitor lower frequency movement on one of the spool pieces, another Sonardyne technology was used: Autonomous Monitoring Transponders(AMTs).

AMTs are most commonly used for long-term survey and monitoring tasks where instruments are needed for acquiring acoustic ranges and sensor data without surface control. They time-stamp data and log it internally, to be retrieved when it’s needed at the surface.

By creating a Long BaseLine (LBL) array of “static” AMTs, to which “mobile” AMTs installed on a spool piece and fitted with sound velocity sensors can range, highly precise measurements of any horizontal movement of that spool piece can be monitored and logged. By fitting the mobile AMTs with Digiquartz pressure transducers, vertical motion could also be tracked accurately within the array.

Before installing the SMARTs and AMTs, Oceaneering surveyed the seabed location. This was done to determine the LBL array design and SMART and mobile AMT positioning. Oceaneering designed and built ROV-installable spool monitoring clamps. This allowed the SMARTs and AMTs to be easily attached to the spool pieces. For the LBL array, four AMTs were placed in tripod stands at predefined locations for optimal ranging.

Following installation, confirmation that all the SMARTs and AMTs were working and a post-installation survey, the autonomous and intelligent instruments were then just left to do their work. A huge benefit of both instruments’ design is that they can be left unattended for three years thanks to their internally monitored lithium primary cells.

Anyone with these instruments deployed in their field has a choice in how to collect the data generated. If it’s close to a topside facility, they can deploy a Sonardyne Dunker 6 transceiver permanently, via a deployment pole for the duration of the monitoring, or temporarily over-the-side, via a winch or A-frame.

If the subsea infrastructure is more remote, they could periodically send a support vessel or an unmanned autonomous surface vessel with a Dunker 6 to harvest the data. For this project, while the site was deep, it was close enough to the customer’s production facility. Oceaneering chose temporary deployments, using the Dunker 6 from an onboard crane, as and when data collection was required.

The results

Since commissioning in the summer of 2018, continuous SMART monitoring of the spools, at four-minute intervals has taken place. Packets of data from both SMART and AMT devices, including raw runtime data, have routinely been sent to the surface. Once received, it has been analysed and used in predictive modelling. This has enabled the operator to calculate the accumulated fatigue and remaining operational design life of their assets.

Gaining access to the spools’ motion characteristics has been invaluable to the operator. It’s data they would have been expensive to access through other means. It has led to a deeper understanding of each spool’s motion frequency, rotation angles and cycle times. Where previously the operator had concerns about the remaining operational life of the spools, they now know the operational life is within the limits of the productive life of the field.

This is a great result for the operator, but also for Oceaneering and Sonardyne. By working together we were able to find a cost-effective and viable solution for the operator and future customers with similar challenges. By combining our expertise and flexible instruments as an integrated solution, the supply chain is able to tackle operators’ deepest challenges, quite literally.

Underpinning the Indian Tsunami early warning system

Sonardyne Bottom Pressure Recorders (BPR) have been at the heart of the Indian Tsunami Early Warning System (ITEWS) since its establishment in 2007. Based on Sonardyne’s workhorse Compatt transponder, our BPR instrument was developed in direct response to the devastating 2004 Indian Ocean Tsunami.

The challenge

30% of India’s population (ca. 420 million) live on its 7,500 km long coast and are consequently highly vulnerable to devastating Tsunamis such as the one that occurred on 26th December 2004. This killed over 230,000 people in the Indian Ocean region, with 10,749 confirmed deaths in India and another 5,640 missing. While seismometers are an important component of Tsunami warning, only Bottom Pressure Recorders can detect the passage of an actual Tsunami. Indeed, Tsunami warnings based purely on seismic data have the potential to produce false alarms, which are costly in wasted evacuations and undermine public confidence.

The essential elements of a Tsunami Detection System (TDS) are:

1. The capability to detect a Tsunami – While a Tsunami may arrive at the coast many metres high, in open ocean they pass almost imperceptibly and may only be a few centimetres in height, although this elevation in sea-level can be maintained for as long as 20 minutes.

2. The functionality to provide this detection ashore with sufficient warning time – A Tsunami travels (in ms^-1) at roughly the square root of the depth of the water (in m) multiplied by the acceleration due to gravity (9.81ms^-1): In short, it travels faster in deeper water, so for example, in 1,000m of water it will be travelling at over 1,100 kmh^-1. In India’s case, the Andaman-Sumatra and Makran subduction zones are located within a few hours Tsunami travel time of the Indian coastline

3. High reliability in delivering the detection information ashore – BPRs, as the name implies are deployed on the seabed, so rely on robust telemetry, which has to operate even in poor weather conditions continuously 24/7/365.

The solution

The catastrophic 2004 Indian Ocean Tsunami led Sonardyne’s founder, John Partridge, to initiate development of a variant of the Compatt 5 seabed transponder to detect a Tsunami passing overhead.

With an extensive track record in the oil and gas industry, this instrument was ideal to form the heart of a TDS requiring very high reliability. Nevertheless, integration of a Digiquartz pressure sensor to enable the Compatt 5 as a BPR, required significant development. This particularly involved reduction of the power required for continuous operation on battery power. Similarly, a new transceiver with low quiescent power, capable of long endurance deployment on a surface telemetry buoy, also had to be developed.

Development was so rapid that when India’s National Institute of Ocean Technology (NIOT) in Chennai, started looking for a TDS in 2005, it was ready for competitive field trial. Sonardyne’s solution was subsequently selected in 2006, leading to deployment of operational systems in the Bay of Bengal and Arabian Sea in 2007.

In normal operation the Digiquartz pressure sensor in the BPR continuously measures water pressure and this data is stored every 15 seconds. The pressure data is then acoustically transmitted every hour to the surface, where an acoustically baffled transceiver, mounted beneath a buoy, receives this data. The buoy is linked to NIOT’s Mission Control Centre (MCC) by satellite communications, so that not only can data be transmitted ashore quickly, but also the health of the BPR is remotely monitored and, if necessary, reconfigured.

Embedded in the BPR is the National Oceanic and Atmospheric Administration’s (NOAA) Tsunami detection algorithm, which compares each measurement to the predicted pressure [Figure]. This predicted pressure uses the previous 3-hour history to take account of tide, weather and temperature variation. Should the difference between the two exceed a programmable default threshold of 3 cm for two consecutive samples, the BPR switches into Tsunami Alert Mode, which then initiates a sequence of data transmissions for the next few hours.

Sonardyne’s Wideband acoustics are central to the functioning of the system, and with the subsequent replacement of the Compatt 5 with Compatt 6, Sonardyne’s latest TDS offering is equipped with the most robust and efficient wideband acoustic telemetry available.

The results

Soon after the first batch of BPRs were deployed, on the 12^th September 2007, the system detected its first Tsunami, which was triggered by an 8.2 magnitude event off the coast of Sumatra at 04° 30’ S 101° 18’ E. How the Tsunami generated was tracked across three of the Indian Tsunami Buoys (ITB) is shown in the gallery.

Located between 1,760 – 2,300 km away, all three stations recorded the seismic ground wave arrival between 7 – 12 mins after the event started. Between 2 – 3 hrs later, the wave itself, which was less than 10 cm in height, passed over the three BPRs, indicating that it had travelled at between 740 – 800 km/h over this period.

Today, Sonardyne’s TDS continues to deliver bottom pressure and event data to NIOT, which is responsible for delivering sea-level data to the Indian Tsunami Early Warning Center (ITEWC) at the Indian National Centre for Ocean Information Sciences (INCOIS) in Hyderabad. In 2014, NIOT reported that system data availability had been 98.83%, with a Mean Time Between Failure (MTBF) of 1.62 years, noting that the majority of these failures were due to external impacts, including weather and human interference with the surface buoys, resulting in damage to surface communication and data systems.

Keeping production flowing by understanding subsea asset movement – wirelessly

An important feature of extending, or even preserving, offshore life of field is to know and understand what is happening with deployed subsea assets. Are they vibrating, perhaps they are slowly walking from their original position, is this happening as a one-off or regularly due to flowline properties? Oceaneering learnt all of this by deploying smart and intelligent sensors at a deep-water development offshore Africa.

The challenge

The worldwide quantity of flowlines, spool pieces, pipeline end termination units, risers and all manner of other installed subsea assets is staggering. All serve as important interconnecting elements in the overall offshore hydrocarbon supply chain. With an aging asset portfolio, it is sometimes very difficult to understand how these assets have been moving during their operational life and what this means to their accumulated fatigue figures and, therefore, safe end-of-life point.

At one offshore field development, Oceaneering, was set a challenge by an international operator. They suspected spool piece movement caused by slugging events, and asked Oceaneering Inc. to provide subsea data for third party analysis so the extent and frequency of movement could be determined. They hoped this would help with the introduction of mitigation measures that would ensure safe and controlled production from the connected producing wells.

With the field located in over 1,000 m of water and with no designed-in points for sensor mounting or hardwired connectivity, this was easier said than done.

The solution

Oceaneering turned to our wirelessly communicating and intelligent monitoring sensors called Subsea Monitoring, Analysis and Report Technology, or SMART for short. Additionally, a series of Autonomous Monitoring Transponders, or AMTs, were deployed within a seabed array to detect any longer period movement that SMARTs would be unable to detect.

Battery operated SMARTs were chosen as they incorporate a low-power inertial measurement unit, or IMU, that can precisely measure the installed sensor’s six degrees of freedom. This means that 3-axes of rotation and 3-axes of acceleration relating to the SMART sensor’s movement can be measured at very high sampling rates over a measurement window set by the operator.

This measurement window, which can be adjusted acoustically at any time from a topside transceiver, can be set between a minimum period of approximately 5 minutes to continuous recording. However, a one-hour measurement window is far more commonplace.

Once the measurement window has ended, SMARTs analyse the recorded raw data, producing and storing one statistical summary file for each window period. When required, these summary files can be requested for wireless transmission through the water column from each SMART’s location to a topside transceiver using Sonardyne’s fast and robust 6G Wideband 2 acoustic protocol on the Dunker 6 LBL and telemetry transceiver.

Importantly for the operator, all SMART raw, time-series, data is securely recorded and saved in-situ for more detailed analysis post-recovery.

Through the combination of edge analytics, low power electronics and acoustic communications, SMARTs could be installed for over a year. Even longer deployments are achievable by supplying larger battery packs or reducing the sampling frequency.

SMARTs are designed for high frequency motion monitoring, but the operator was equally concerned that longer periods of motion were in play that may have caused the subsea asset to gradually move from its installed position. Thus, monitoring for possible flow induced vibration (FIV) and vortex induced vibration (VIV) was also required. To monitor this motion, Oceaneering Inc. chose another Sonardyne sensor called an AMT.

AMTs are used for long-term survey and monitoring applications where instruments are needed to acquire acoustic ranges and other sensor data, like pressure, temperature, and sound velocities, without any surface control. By creating a Long Base Line (LBL) array of static seabed located AMTs with an AMT on the asset needing to be monitored, highly accurate measurements of any horizontal movement of the monitored asset can be measured, accurately timestamped, and logged. Vertical movement of the asset-mounted AMT can also be determined by the recording of precise pressure sensor information and comparing it to those from the control array.

An additional benefit identified by Oceaneering is that data from the AMTs can be wirelessly recovered using the same topside hardware as that of the SMART, resulting in less topside subsystems.

The results

Oceaneering mobilised the equipment in 2018 and it has been in operation ever since. The performance of the SMARTs in determining motion characteristics, coupled with the motion mitigation measures that were introduced, enabled the operator to continue producing safely and within the design life of the installed spool pieces. What’s more, the operator now has a far better understanding of their accumulated fatigue figures for the spool pieces and is able to determine the safe end-of-life point for their subsea assets.

Rapid leak detection for subsea production and storage sites

The ocean is a critical habitat that needs protecting. With decades of experience in sonar detection systems, our technologies provide an essential early subsea leak detection and warning system, across your oil and gas assets, CO₂ storage and offshore hydrogen transport and storage sites.

The challenge

A supermajor international energy company, with production infrastructure in more than 2,000 m (6,500 ft) of water depth, wanted a single subsea leak detection system that could be permanently installed to detect and localise, within seconds, oil or gas leaks across a wide area of its subsea infrastructure.

Existing sonar-based solutions are mostly based on sensors attached to subsea assets to detect leaks at specific or very localised locations, i.e. within a few metres. Alternative, non-acoustic, systems rely on anomalies in production data rates, which can be challenging should the leak occur upstream of the monitoring device.

At worst, leak detection relies on viewing the leak at the sea surface in the form of an oil-based sheen – when it’s already too late. This option is also limited when it comes to detecting leaks at gas producing fields and offshore carbon capture and storage (CCS) sites.

With a globally significant installed and aging asset base, as well as new infrastructure in the form of offshore CO₂ and hydrogen transport and storage, there’s increasing interest in alternative leak detection technologies that can operate autonomously and sustainably over wide areas in all water depths.

The solution

Developed by Wavefront Systems and manufactured and commercialised by Sonardyne, our Sentry Integrity Monitoring Sonar (IMS) is the only commercially available wide-area subsea leak detection system. A single Sentry head can provide 360-degree coverage of a 1,200 m diameter area, or more than one billion cubic feet of seawater, automatically alerting the operator as soon as an oil or gas leak is detected.

Detection rates are very impressive, with Sentry being able to detect monophase gas down to 0.1 litre per minute (equivalent to around 1 barrel of oil per day) or monophase oil to 1 litre per minute (equivalent to 9 barrels of oil per day). That means operators can react quickly to an infrastructure integrity breach before it becomes a bigger environmental and financial problem.

Sentry is an active acoustic-based solution that is based on a remotely operated vehicle (ROV) deployable low-power sonar proven for long-term monitoring. It’s available as a wired solution, that can be connected via existing subsea infrastructure directly into a surface asset. There, a Sentry workstation with graphical user interface (GUI) is able to provide users with clear real-time and automatic alerts of any oil or gas leaks.

It’s also available as a wireless, battery-powered solution for semi-permanent deployment, with data transmitted acoustically to a topside transceiver system. The transceiver can be deployed from a platform, buoy, vessel of opportunity or, now more commonly, via uncrewed surface vehicles (USVs).

The results

To make sure Sentry was fit for the oil major’s needs, the operator oversaw a trial deployment of a hardwired Sentry IMS. This included using a simulated monophase oil target, in this case nitrile-rubber strands, equivalent to a nominal oil leak rate of around 150 barrels per day.

The trials provided fast and accurate results. Detection and classification of the equivalent release of 100 barrels of oil per day out to 245 m (820 ft) was achieved, a distance constrained only by limitations of the trial set up. Leak detection was alerted within seconds of the simulated leak skid being deployed.

Sentry’s capability, however, covers 100 barrels per day mono-phase oil leaks at distances of up to 740 m (2,427 ft). It is even more sensitive to mono-phase gas leaks, with the system being capable of detecting down to the equivalent of just 1 barrel per day at 500 m (1,640 feet) or 100 barrels per day (as measured at depth) at 1,000 m (3,280 ft).

Following the extensive and successful trials, the operator purchased the Sentry IMS system for installation at its deep-water field development.

Supporting the energy transition

As we transition from fossil fuels to new energies, many are looking to offshore as potential sites for CCS, as well as for hydrogen production.

Sentry helps to de-risk these projects. It ensures that, should carbon sequestration and offshore hydrogen transport and storage sites develop a leak, their operators will be alerted quickly, enabling a swift response, preventing larger environmental and financial problems.

Read about how we proved subsea leak detection capability for carbon capture and storage sites (CCS) through an Energy Technologies Institute research project, with partners Fugro, National Oceanography Centre, British Geological Survey and Plymouth Marine Laboratory here.