Long endurance monitoring of tectonic motion

Subduction zones are tectonic plate collision boundaries where typically higher density oceanic crust is being pushed under continental crust. This is one of the most important processes in the evolution of the Earth’s morphology.

The challenge

Subduction zones comprise extremely large thrust faults, known as megathrusts, and are the source of the world’s most dangerous volcanoes and earthquakes. In between larger earthquakes, megathrusts comprise complex heterogeneous distributions of locking and therefore strain accumulation.

On land, GPS and laser observations enable precise geodetic measurements. Until recently, the inability to undertake cost-effective complementary observations subsea in the outermost subduction zone offshore, has been a critical flaw. This is where much of the elastic strain build-up and release occurs. Improving scientific understanding of the seafloor movement in these regions is an important basis for future seismic hazard assessment.

The solution

In response to this challenge, Sonardyne has worked with a number of research institutes, including GEOMAR, to supply networks of Autonomous Monitoring Transponders (AMTs ) – seabed instruments that are capable of taking hundreds of thousands of stable, highly precise geodetic observations, safely log the data and on command, wirelessly transmit it up to the surface.

Originally developed for the offshore industry to precisely measure vertical and horizontal seabed displacements caused by reservoir depletion, AMT is a long-life (up to five years depending configuration), deep-rated acoustic instrument fitted with high resolution pressure, sound velocity and temperature sensors. All of this is built around our 6G hardware platform and Wideband 2 digital signal technology.

AMTs run a fully automated logging regime gathering acoustic travel time (range) between neighbouring units, pressure, sound velocity, temperature and tilt data at intervals defined by the user. A passing AUV, vessel of opportunity, gateway buoy or unmanned surface platform can harvest data on demand and at any point, the user may amend the logging regime of any or all of the AMTs, using the bi-directional communications link.

GEOMAR have now deployed three AMT seabed arrays in Chilean seas. The largest array is the Geodetic Earthquake Observatory on the SEAfloor (GeoSEA) project, offshore northern Chile on the Nazca-South American plate boundary.

The last rupture resulting in a major earthquake at the array location was in 1877. This was identified as a seismic gap prior to the 2014 Iquique/ Pisagua 8.1 magnitude earthquake.

Nevertheless, the southern portion of the segment remains unbroken by recent earthquake activity and so, with the two plates converging at a rate of around 65 millimetres per year, new tension is being continuously built up. ‘Therefore the region is a focus site for seismologists to understand strain build-up prior to an earthquake,” says Professor Kopp

The GeoSEA array consists of 23 AMTs deployed from the German Research Vessel Sonne in late 2015 and comprises three sub-arrays that monitor different sections of the megathrust. The tectonic nature of the seabed gives rise to a variety of complex topographies.

Sonardyne’s in-house Survey Support Group worked closely with scientists from GEOMAR to plan the subarray layouts. Positioning of the AMTs were based on multibeam data collected during the preceding research leg. Precise placement in the order of a few tens of metres was required and in one case, an AMT had to be sited on a ledge on the side of a ridge that was only 50 metres wide and 150 metres long.

The first area is located on the middle continental slope between the main trench and the Chile coast and consists of eight transponders laid in pairs on a stairway-like feature of four topographic ridges at a depth of around 2,800 metres. The ridges, which are surface expressions of faults at depth, are approximately 100 metres high with around an 800 metre flat area between.

On the opposite (seaward) side of the trench from Chile, a further five AMTs were deployed in depths approaching 4,100 metres to monitor extension across plate bending related normal faults. Here, faulting of the Nazca Plate is caused by stretching of its surface as it is pushed downwards under the South American plate, and thus the fault lines are relatively new and active. The AMTs were laid at the intersection of multiple fault lines separating three or four blocks, with two being placed on the same block to provide a sound speed reference baseline.

The deepest area, located between 5,100 and 5,400 metres deep, is on the lower continental slope and comprises a circular pattern of eight AMTs surrounding two central instruments. This pattern provides a variety of short and long baselines to measure diffuse strain build-up in a highly faulted area made up of separate geological blocks, which are under high compression.

To cope with these extreme conditions, the AMTs used for the GeoSEA project are 6,000 metre-rated Lower Medium Frequency (LMF 14-19 kHz) omnidirectional units. Sampling at rates between one and a half and three hours, the GeoSEA AMTs are planned for an initial three and a half year deployment. However, the four metre high seabed frame in which each unit sits enables it to be easily removed by ROV, returned to the surface to allow its battery to be exchanged then placed back in the frame in the same position – giving scientists the option of extending the survey if required.

The results

Since initial deployment, data from the array has been recovered by a US research ship using a Sonardyne HPT 7000 dunking modem deployed over the side, as well as GEOMAR’s GeoSURF Wave Glider, equipped with a 6G acoustic communication module fitted in its hull.

“Overall, our experience with Sonardynes instruments is superb and our results have been beyond our expectations. It has been a pleasure for us to work with infrastructure that we can fully rely on.” Professor Kopp from GEOMAR commented.

The success of the AMT’s performance in the Nazca-South American plate boundary arrays has resulted in two smaller arrays in the Sea of Marmara off Turkey and on the submerged flanks of Mount Etna. Although the results of these surveys were yet to be published at the time of writing, scientists were excited by the new opportunities Sonardyne’s technology offers.

GEOMAR’s Doctor Dietrich Lange summarises that, “With this approach, we are taking a new path in earthquake research since previously, measurements of a few millimetres, were hardly possible.”

Deepwater structure installation made easy

For five decades, we’ve been working to make subsea developments safer, cleaner and more efficient than ever before. Our aim is always to mitigate risk for our partners, reduce the complexity of deepwater structure installations and increase efficiencies so projects cost less and teams spend less time offshore.

The challenge

When offshore contractor China Offshore Fugro Geosolutions (COFG) approached us looking for ways to improve the installation of multiple deepwater structures, we were excited to support their operation. The project required the installation of four pipeline end terminations. Measuring up to 15 m long, 10 m high and weighing as much as 45 tonnes each, the challenge was to accurately place each structure efficiently and reduce the time needed for the project to be completed.

These kinds of deepwater installations are usually done by installing a gyro frame and placing a subsea gyro into it, with a battery, a modem, sound velocity sensor, and maybe also a depth sensor. These then need to be wired up, turned on, and fingers crossed that it’ll all work. The various connections, components and necessary wiring between each, create multiple opportunities for things to go wrong.

The solution

Gyro Compatt 6 is a compact and versatile positioning transponder with a subsea gyro used to simplify structure positioning. From one instrument everything can be monitored and controlled from the topside using our Ranger 2 6G Ultra-Short BaseLine (USBL) positioning system or Fusion 1 or 2 Long BaseLine (LBL) software. What’s more, it’s quick to recharge on deck, making it a perfect choice for multi-structure installation campaigns.

Onboard the HSYS 201, COFG already use our Ranger 2 USBL positioning system, our Fusion LBL software and a ROVNav 6 transceiver onboard their ROV, all of which work seamlessly with our 6G USBL family of products, of which the Gyro Compatt 6 is a part.

This compact unit is much more than a positioning transponder. The unit combines an LBL transponder Wideband acoustic positioning, Lodestar attitude and heading reference sensor (AHRS), a depth sensor and sound velocity, plus an integrated high-speed acoustic modem. By combining these technologies into one small unit, a single yet highly versatile and easy to install instrument can provide high update rate wireless attitude, heading, heave, surge, sway, pressure, sound speed and acoustic positioning of any subsea object.

There is no need for the traditional gyro frame and subsea gyro technique and all the wiring and crossing of fingers that goes along with it. By deploying the Gyro Compatt 6, ranges from the LBL array can be gathered in real time by a ROVNav 6 LBL ROV transceiver onboard the ROV, and, in turn, tracked in the LBL array.

The results

With just the Gyro Compatt 6 installed and secured for structure monitoring, COFG’s installations were successfully carried out on the Liuhua 29-1 gas field development in water depths ranging from 520 m to 1120 m, between mid-October and the end of November 2019. Each of the four installations was made much easier – with reduced stress, fewer complications and in less time.

Jia Wu, Operation Manager, Engineering Survey Division at China Offshore Fugro Geosolutions (Shenzen) Co. was pleased with how their Gyro Compatt 6 performed.

“This all-in-one system offers us the biggest advantage for the operation, being easier to use, smaller in size and more efficient for preparation,” he says. “It is more convenient to secure as well as recover and does not require wiring between components, compared with a conventional gyro basket (transponder plus battery plus gyro).”

Do you need to simplify a deep water structure installation project? Speak with an expert today.

Greater efficiency, lower overheads, with underwater autonomy in deepwater seismic

Shell Brasil, in partnership with Petrobras, Sonardyne and Brazilian research institute SENAI CIMATEC are working together to bring a step-change to 4D seismic data gathering in Brazil’s deepwater pre-salt region.

Discover how we’re collaborating to develop innovative autonomous technology that will make monitoring these challenging deepwater fields more efficient, with fewer people and lower environmental footprint.

Scroll down to read this case study in Portuguese.

The challenge

Seismic data is an essential part of offshore field development activity, especially to support proactive reservoir management and production optimisation. Techniques for gathering this data have evolved dramatically over the decades; from the use of marine streamers for large exploration seismic campaigns to the now routine use of remote operated vehicles (ROV) to deploy ocean bottom nodes (OBN) for high-resolution imaging of pre-salt reservoirs.

Yet, gathering seismic data for pre-salt reservoir imaging remains intensive work. It involves large, costly and carbon-emitting crewed vessels for deployment and recovery of, typically, thousands of nodes. As an example, for a 10-month campaign over one of Brazil’s giant pre-salt fields, a node handling vessel could emit close to 10,000 tons of CO₂. Costly and complex operations can mean a reduction in frequency of surveys, including of those done to gather what’s called time lapse or 4D seismic data, which is required to monitor the pre-salt reservoirs.

Shell and Petrobras came to us believing that there could be a lower-cost, more sustainable, way of acquiring 4D seismic data, as well as other parameters such as seafloor subsidence, to help better monitor reservoirs. They also saw this could be done with a lower environmental footprint and while keeping more people safe.

The solution

Together, Shell Brasil, Petrobras, and Sonardyne joined forces with SENAI CIMATEC to develop an advanced seismic data acquisition system under a Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) promoted research and development project.

At its core is an On-Demand Ocean Bottom Node, or OD OBN. This semi-permanent seabed system is used for the acquisition of high resolution seismic and seafloor subsidence data.

Like conventional seabed nodes (OBN), each OD OBN contains three geophones and one hydrophone, a data recording system, batteries and a highly accurate clock. The sensors detect pressure waves emitted by an airgun source, usually towed by a ship, as they are reflected upwards towards the seabed from the underlying layers of rock surrounding the reservoir.

Unlike conventional nodes, these OD OBNs remain on the seabed, down to 3,000 m, gathering seismic data for up to five years. This significantly reduces the cost of repeated ocean bottom seismic campaigns, as the node handling vessel is removed from the operations. It also reduces the impact on the environment and marine ecosystems.

The activation of the nodes, verification of subsidence event alarms, calibration of internal clocks and harvesting of seismic data will be performed using an autonomous underwater vehicle (AUV) called Flatfish developed, in a closely interlinked ANP project, by partners Shell Brasil, Petrobras, SENAI CIMATEC and Saipem.

Flatfish will find each node using Sonardyne’s 6th generation (6G) of acoustic positioning systems. Our acoustics will also support data telemetry with the nodes, for health checks, configuration and acoustic time synchronization. The Flatfish will then hover above each node, in turn. Using an extremely high bandwidth and energy efficient laser-based variant of Sonardyne´s BlueComm optical communications device, it will wirelessly harvest many gigabytes of seismic data in just a few minutes.

This variant uses two rapidly modulated lasers to produce simultaneous bi-directional communications over more than five meters range. It is optimised for peak data transfer performance, with speeds of over 600 megabits per second demonstrated. This makes it excellent for harvesting large amounts of data from seabed nodes.

“Using OD OBN in combination with Flatfish, a 4D seismic campaign in the pre-salt may be executed in a simpler manner, with lower operational cost, lower risk of human exposure and lower environmental impact,” says Jorge Lopez, Manager of Subsurface Technology at Shell Brasil. “On top of this, the nodes also measure seafloor deformation and can continuously monitor for possible subsidence events that may occur during the production of the field.”

The results

In the first phase of the OD OBN project, eight fully functional prototype nodes were built. These comprised of two different concept types and were designed and built by SENAI CIMATEC in Salvador, Bahia together with Sonardyne Brasil.

In 2021, initial tests of seismic data recording were conducted at the Sapinhoá pre-salt field offshore Brazil and interoperability tests between the nodes and the Flatfish AUV were performed in shallow water in Trieste, Italy.

A very intensive laboratory and offshore testing and demonstration program is being conducted over the next 18 months to ensure the OD OBN system meets its operational requirements. This program will increase the maturity of the solution, with tests in pre-salt fields for recording seismic data with the OD OBN prototypes and the communication and data harvesting AUV missions.

In the next phase of the project, starting later in 2022, Shell and Petrobras will sign a new agreement to manufacture 600 nodes and deploy them for three years of reservoir monitoring in a Brazilian pre-salt field.

Maior eficiência, baixo custo de operação, para sísmica em águas profundas através de autonomia submarina

A Shell Brasil, em parceria com a Petrobras, a Sonardyne e o instituto de pesquisa brasileiro SENAI CIMATEC estão trabalhando juntos para trazer uma mudança radical na coleta de dados sísmicos 4D na região do pré-sal em águas profundas do Brasil.

Descubra como estamos colaborando para desenvolver tecnologia autônoma inovadora que tornará o monitoramento desses desafiadores campos em águas profundas mais eficiente, com menos pessoas e menor impacto ambiental.

O desafio

Os dados sísmicos são uma parte essencial da atividade de desenvolvimento de campos offshore, especialmente para apoiar o gerenciamento proativo de reservatórios e a otimização da produção. As técnicas para coletar esses dados evoluíram dramaticamente ao longo das décadas; desde o uso de streamers marinhos para grandes campanhas sísmicas de exploração até o uso rotineiro de veículos operados remotamente (ROV) para implantar nós de fundo oceânico (OBN) para imagens de alta resolução de reservatórios do pré-sal.

No entanto, a coleta de dados sísmicos para imagens de reservatórios do pré-sal continua sendo um trabalho intensivo. Envolve embarcações tripuladas grandes, caras e emissoras de carbono para implantação e recuperação de, normalmente, milhares de nós. Como exemplo, para uma campanha de 10 meses em um dos campos gigantes do pré-sal brasileiro, uma embarcação de manuseio de nós pode emitir cerca de 10.000 toneladas de CO₂. Operações caras e complexas podem reduzir a frequência de levantamentos, inclusive daqueles feitos para coletar o lapso temporal que é chamado de  dados sísmicos 4D, necessários para monitorar os reservatórios do pré-sal.

A Shell e a Petrobras nos procuraram acreditando que poderia haver uma forma mais barata e sustentável de adquirir dados sísmicos 4D, além de outros parâmetros, como subsidência do fundo do mar, para ajudar a monitorar melhor os reservatórios. Eles também viram que isso poderia ser feito com um impacto ambiental menor e mantendo mais pessoas seguras.

A solução

Juntos, Shell Brasil, Petrobras e Sonardyne uniram forças com o SENAI CIMATEC para desenvolver um sistema avançado de aquisição de dados sísmicos em um projeto de pesquisa e desenvolvimento promovido pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP).

Em seu núcleo está um On-Demand Ocean Bottom Node, ou OD OBN. Este sistema semipermanente do fundo do mar é usado para a aquisição de dados sísmicos de alta resolução e subsidência do fundo do mar.

Assim como os nós convencionais do fundo do mar (OBN), cada OD OBN contém três geofones e um hidrofone, um sistema de gravação de dados, baterias e um relógio de alta precisão. Os sensores detectam ondas de pressão emitidas por uma fonte do tipo airgun, rebocada por um navio, à medida que são refletidas para cima em direção ao fundo do mar a partir das camadas subjacentes de rocha ao redor do reservatório.

Ao contrário dos nós convencionais, os OD OBNs permanecem no fundo do mar, até 3.000 m, coletando dados sísmicos por até cinco anos. Isso reduz significativamente o custo de repetidas campanhas sísmicas no fundo do oceano, uma vez que a embarcação de manuseio de nós é removida das operações. Também reduz o impacto no meio ambiente e nos ecossistemas marinhos.

A ativação dos nós, a verificação dos alarmes dos eventos de subsidência, a calibração dos relógios internos e a coleta dos dados sísmicos serão realizados por meio de um veículo submarino autônomo (AUV) denominado Flatfish, desenvolvido em um projeto ANP estreitamente interligado, pelos parceiros Shell Brasil, Petrobras, SENAI CIMATEC e Saipem.

O Flatfish encontrará cada nó usando a 6ª geração (6G) de sistemas de posicionamento acústico da Sonardyne. Nossa acústica também suportará telemetria de dados com os nós, para verificações de integridade, configuração e sincronização de tempo acústico. O Flatfish irá então pairar acima de cada nó, por sua vez. Usando uma largura de banda extremamente alta e uma variante baseada em laser com eficiência energética do dispositivo de comunicação óptica BlueComm da Sonardyne, ele coletará sem fio muitos gigabytes de dados sísmicos em apenas alguns minutos.

Esta variante usa dois lasers modulados rapidamente para produzir comunicações bidirecionais simultâneas em um alcance de mais de cinco metros. Ele é otimizado para desempenho de transferência de dados de pico, com velocidades demonstradas de mais de 600 megabits por segundo. Isso o torna excelente para coletar grandes quantidades de dados de nós do fundo do mar.

“Usando OD OBN em combinação com o Flatfish, uma campanha sísmica 4D no pré-sal pode ser executada de forma mais simples, com menor custo operacional, menor risco de exposição humana e menor impacto ambiental”, afirma Jorge Lopez, Gerente de Tecnologia de Subsuperfície da Shell Brasil. “Além disso, os nós também medem a deformação do fundo do mar e podem monitorar continuamente possíveis eventos de subsidência que podem ocorrer durante a produção do campo”.

Os resultados

Na primeira fase do projeto OD OBN, doze nós protótipos totalmente funcionais foram construídos. Estes são compostos por dois tipos de conceito diferentes e foram projetados e construídos pelo SENAI CIMATEC em Salvador, Bahia em conjunto com a Sonardyne Brasil.

Em 2021, os testes iniciais de registro de dados sísmicos foram realizados no campo do pré-sal de Sapinhoá no litoral brasileiro e os testes de interoperabilidade entre os nós e o Flatfish AUV foram realizados em águas rasas em Trieste, Itália.

Um intenso trabalho em laboratório  e um programa de demonstração e testes offshore estará sendo realizado nos próximos 18 meses para garantir que o sistema OD OBN atenda aos seus requisitos operacionais. Este programa aumentará a maturidade da solução, com testes em campos do pré-sal para registro de dados sísmicos com os protótipos OD OBN e as missões AUV de comunicação e coleta de dados.

Na próxima fase do projeto, a partir do final de 2022, a Shell e a Petrobras assinarão um novo acordo para fabricar 600 nós e implantá-los para três anos de monitoramento de reservatórios num campo do pré-sal brasileiro.

A SMART deepwater invention

Operations in deepwater are a significant challenge requiring the latest generation of subsea equipment and installation techniques. While the majority of operations do go to plan, there are occasions when they don’t and an innovative approach to deepwater intervention is required.

The challenge

Houston headquartered engineering specialists Trendsetter Vulcan Offshore (TVO) were set just such a difficult deepwater intervention challenge. They were brought in to help an operator rectify a completed wellhead at a deepwater site that had suffered from misalignment. The wellhead, which was in more than 2,000 m water depth, had been bent and there were concerns other components might have been damaged.

TVO were tasked with finding a solution to bringing it back to a vertical position. This would allow intervention access to the well for remediation and abandonment operations, so it could be permanently sealed. A key challenge was to carry out this work extremely carefully and in a controlled manner, in order to prevent any further potential damage to the wellhead.

The solution

TVO came up with an innovative solution to the problem. It proposed a ring of six subsea tensioning systems, mounted on suction piles positioned in a ring on the seafloor around the wellhead. Each one would be connected via a rope to a Trendsetter-supplied lower riser package (LRP) installed onto the wellhead. By carefully tensioning the ropes, they would be able to then bring the wellhead back into an upright position.

To do this in a safe and controlled way, TVO required a monitoring system which would provide:

• Near real-time feedback of the tension data at each of six load pins installed on the LRP (one each for each of the six tensioners).
• Near real-time inclination data from the wellhead itself

Conventional deepwater intervention solutions

Traditionally, inclination data is acquired by visually checking subsea bullseye levels attached to a structure using a diver, or, in this water depth, a remotely operated vehicle (ROV). Similarly, visual displays on the tensioning systems would be the source of the tension data, also read using an ROV.

However, these techniques add a significant amount of time, given the 30-40 m radius of the circle of tensioning systems, even if, as was the plan, only two would need to be actively tensioned during the righting operation. Bullseyes can also be mis-read.

Another alternative option is to deploy battery powered accelerator and inclinometer measuring bottles, using an ROV. But these would have to be retrieved to the surface after each measurement, so would also mean a lengthy operation, potentially taking days.

Taking an alternative, SMART, real-time intervention approach

Instead, TVO proposed and successfully deployed a wireless, intelligent, digital underwater monitoring solution. This provided near real-time inclination and tension data to the operations team at the surface (around three minutes delay). It comprised of two of Sonardyne’s Subsea Monitoring, Analysis and Reporting Technology (SMART) and six Compatt 6 transponders.

The internal inertial measurement unit in each SMART was used to calculate pitch and roll data from two points either side of the LRP, allowing TVO to calculate the wellhead’s bend angle in the local coordinate frame.

This data was then transmitted acoustically, using the SMART’s internal modem, to the surface at three-minute intervals. The Compatt 6s were interfaced with the load cell shackles at each tensioner point on the LRP and transmitted the tension readings to the surface at less than one-minute updates.

The results

The righting operation took just three hours, using an ROV to tension the winches at two key tensioning units, one at a time. In comparison, using the alternative methods would have taken days. Throughout, the TVO team and the operator were able to view a constant near real-time visualization of the inclination of the wellhead and the tension that was being applied at each tensioning system. This was done via an internet-based dashboard developed by TVO, so that any member of the wider team, including the operator, from anywhere in the world could watch.

Making a SMART decision

“It was a very unique challenge. There were a lot of studies and approaches analysed within the customer group before making a decision to what the right approach was. They chose ours, using Sonardyne’s SMARTs and Compatt 6s, and it worked very well,” says TVO’s Kim Mittendorf.

“We really could control the two tensioners with the amount of tension we needed in near-real time. While the ROV was tensioning the winch, more than 2,000 m below us, we could see what direction the wellhead was moving in, how the pitch and roll angle changed.

“All the data was also live streamed to a website so that the customer, offshore and onshore, could monitor the operation in near-real time. This drove their decision making and gave them the comfort to continue with the operation as planned.”

Paving the way for a safe well abandonment

Following the righting of the wellhead, the tensioning and monitoring system was kept in place to allow safe intervention and final abandonment operations to be completed. During this phase, the data transmission rates were reduced to once every few hours.

For redundancy, two of the suction piles had relay Compatt 6s installed on them. This was due to a concern that direct line of sight to the transceiver from one or more of the Compatt 6s wouldn’t be possible.

In addition, the ROV had a ROVNav 6 transceiver, as another backup communications pathway. However, none of these were required as the LRP located SMARTs and the six Compatt 6s connected to the load pins were able to directly communicate with the topside transceiver.

Deepwater wireless well intervention success

The entire campaign proved to be a complete success. Thanks to TVO’s engineering and Sonardyne’s monitoring technologies, the operator was able to safely and efficiently decommission this challenging deepwater wellhead.

Initial skepticism from the operator in using a hydro-acoustic approach for data transmission was also overcome and through the success of the project, further confidence has been built into the technology for future applications.

Transponders provide reliable releases for Allton offshore Norway

When placing vital equipment such as Nodes on the seabed you need to be sure that you can retrieve them. During the development process, a lack of other products available in the marketplace that met their requirements led Norwegian technology and service company Allton to turn to Sonardyne for a solution.

Starting life as Petromarker in 2005, Allton has been operating offshore Norway for almost 20 years. The company specialises in: marine subsurface electro-magnetic (EM) data acquisition and imaging for hydrocarbon exploration and production, CO₂ measurement, monitoring and verification for carbon capture sequestration and marine mineral exploration. It has now expanded its technology and service offering to include multiphysics joint acquisition of both EM and seismic OBN data.

With their innovative multiphysics platform relying on the data they retrieve from both EM and seismic OBN nodes, Allton need to be one hundred percent confident that they can locate and recover their nodes once they’ve been deployed. This can be from depths of up to 3,500 m in often challenging conditions.

When Allton expanded its operational work department and began the redesign of its subsea equipment, a search began for new and reliable solutions as existing transponders and release mechanisms were unsuitable for their specific requirements.

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.

Overview

Acoustic release transponders are a vital pieces of ocean equipment – relied upon by energy, defence and science users to moor valuable equipment strings for years at a time, and when commanded to do so, reliably return equipment and logged data to the surface.

Transponders need to be tough, reliable and easy to work with. The RT 6-HD meets these requirements.

Part of our new range of acoustic releases, RT 6-HD combines the extensive mechanical design track record with the flexibility of our 6G platform, resulting in enhanced battery life and perhaps most significantly, compatibility with our Ranger 2 USBL system.

At a glance

• Tested, loaded, deployed and released with Deck Topside
• Also works with Ranger 2 USBL to lift, lower and track heavy subsea structures in deep water
• Working Load Limit 2,500 kg (4:1)
• Depth rated to 7,000 m
• Highly reliable release mechanism
• Compact and rugged design

With RT 6-HD, you use your vessel’s Ranger 2 USBL to deploy, track, locate and command the instrument – removing the need for a separate topside unit. If you don’t have access to a Ranger 2 USBL, our rugged and lightweight Deck Topside with an over-the-side dunker is all you need to both configure and command RT 6-3000s.

With a WLL of 2,500 kg (at 4:1), twice that of our RT 6-3000 and RT 6-6000, RT-HD is designed for specialist heavy lift application scenarios such as deep water construction and salvage.

RT 6-HD is also our deepest rated acoustic release transponder at 7,000 m. Excellent corrosion resistance is achieved by using super duplex stainless steel for the housing materials.

RT 6-HD is configured with our iWand hand-held acoustic transponder test and configuration device.