Having access to qualified and regularly updated knowledge about the integrity of your subsea assets and reservoir conditions is of utmost importance for making the right decisions at the right time. The solution is continuous subsea asset monitoring monitoring throughout the life of field. Global business manager for Subsea Asset Monitoring, Stephen Fasham, reviews Sonardyne’s capabilities and describes how they’re creating smarter links between the seabed and the analyst’s desktop.

Subsea Asset MONITORING

The purpose of subsea asset monitoring is to understand how subsea systems are performing, as well as enabling faults to be detected at an early stage. The data generated by monitoring systems needs to be analysed in order to determine if the integrity of the system is jeopardised and decide on what potential actions should be performed. This analysis can be carried out at the surface, but in some cases, where large data volumes are generated subsea, moving the data processing subsea enables systems to operate autonomously – warning the operator when predefined thresholds are exceeded. By managing the data actively, systems can have long operating times whilst still being battery operated.

For example, risers for both drilling and production are increasingly requiring robust, long-term instrumentation to give manufacturers, contractors and operators a real-time scorecard on the cyclic abuse Mother Nature dishes out, and how much remaining life is in their equipment as a result. Information including; position, inclination and water current profile for risers, riser towers, mooring lines and turret buoys can be determined using multi-function Sonardyne 6G transponders as part of an integrity monitoring solution.

The value of the monitoring system can be enhanced by connecting external sensors which use the transponders to telemeter data to the topside for analysis. By way of example, ultrasonic corrosion monitoring allows users to determine the current extent and predict the future corrosion of the metallic parts of the structure.

As the capability of monitoring equipment improves, and the benefits for production efficiency and savings on inspection and maintenance regimes are demonstrated, asset monitoring looks set to be a growth sector for the future.

1 Data Telemetry Solutions

Subsea wireless telemetry is useful in the oil and gas industry where subsea valves and actuators need to be controlled or monitored at the surface. Sonardyne has an unrivalled portfolio of acoustic and non-acoustic wireless communications technologies and systems for use in the harshest of offshore environments.

AMT interfaced to a ADCP for data acquisitionOur acoustic systems are proven to perform robustly in areas of high ambient noise and reverberation caused by proximity to vessels, subsea structures and ROVs. For this reason, we are repeatedly called upon to provide clients with equipment and systems where high reliability is imperative. Our 6th generation (6G) acoustic instruments, which are the basis of our acoustic communications solutions, provide unprecedented levels of flexibility in terms of frequency, transmission power level and user data transfer rate.

The versatility of 6G enables Sonardyne to tailor the equipment configuration to match the application as well as the prevailing acoustic conditions. Where telemetry needs are allied to a positioning requirement – often the case when working with Floating Production Storage and Offloading (FPSO) vessels – a Sonardyne USBL positioning transceiver can double-up as a data modem. Should the monitoring system only require wireless data transfer, the surface transceiver can be a winch-deployed dunker. Options for subsea transponders are extensive, and include long-life battery packs and housing materials matched to the deployment location; warm or cold, deep or shallow.

As well as point-to-point links, Sonardyne is also able to provide solutions beyond the normal range of a single acoustic communication link. Data hopping along a chain of subsea units significantly extends range, with systems in the field connecting wellhead sensors to vessels over 10 kilometres away through difficult seabed conditions.

A more recent addition to the Sonardyne communications product portfolio is BlueComm, which adds Free Space Optical (FSO) communications to established acoustic products. BlueComm uses high power LED emitters to provide data links with up to 20 Mbps bandwidth, over distances up to 200 metres. For the first time, BlueComm enables customers to collect large payloads of sensor data without needing to recover instrumentation to the surface. BlueComm has been used to recover sensor data from subsea observatories at depths of over 2,000 metres.

The high data rate has also been demonstrated for wireless transmission of high definition video signals, providing the option for ROVs to deploy remote wireless cameras and observe complex operations from multiple viewpoints.

BlueComm has also demonstrated its capability for tetherless vehicle control, where it can be integrated with an acoustic system to provide longer range communications and/ or backup should the optical channel be disrupted. BlueComm is a game changer. It has moved subsea communications systems from the equivalent of dial-up to broadband. By making high speed wireless connections a reality, BlueComm opens up new applications where wired systems are impractical or unaffordable.

2 Application Solutions

6G transponder provideds high update rate for bundle tow monitoringWhilst our 6G telemetry products can be used ‘simply’ to transfer data from external sensors, where we differ from other acoustic communications providers is in how we use our engineering capability to take leading products and systems and evolve them to meet the changing needs of our customers. That includes integration of third party sensors and systems that interface to external systems. It’s what many would call ‘a complete application solution.’

An example of one such application is the provision of acoustic monitoring systems for pipeline bundle tow operations. Engineering requirements here are complex, requiring positioning and monitoring transponders to be mounted at regular intervals along the entire length of the pipe bundle.

This aids in control of the shape of the bundle, as well as providing pipe pressure, tow tension, heading, roll and pitch from inertial sensors and flooding valve control. All this with a less than 30 second update rate – as data is relayed acoustically up the pipeline to the tug or survey boat. This particular technique is now tried and tested, having been used for many years for pipeline bundles which can now be as long as 10 kilometres.

3 Downhole sensor loggers

By definition, a standalone data logger is a data capturing device that, once initialised, can log automatically data and store it in its on-board memory. Data stored in memory can be ‘harvested’ acoustically and downloaded into a computer for analysis to provide information on the history of parameters or events.

Sonardyne’s Acoustic Data Logger has a track record of more than 25 years of successful installations, with the current generation incorporating Sonardyne’s Wideband acoustic technology in a design which allows the subsea unit to be deployed and retrieved by an ROV.

When combined with the feature of ROV portability, the system is the ideal solution for initial well appraisal, where frequent downhole pressure and temperature readings need to be logged over a period of a few weeks. These units can then be redeployed to another well, making them a very cost-effective solution for reservoir evaluation. However, the new system is equally suitable for long-term deployments where it can be left installed on a wellhead – logging data for several years without intervention.

The subsea unit can be interfaced to all industry standard downhole gauges, whilst custom interfaces can be supplied on request. Logging intervals can be varied by acoustic command from1minute to 7 days, a feature governed by the battery power consumed by the gauges and interface circuitry each time a measurement is made. Using a standard battery, the life will be greater than two years if gauges are read only a few times per day, but may reduce to a few weeks if gauges are read every few minutes.

The flexibility of the system enables additional external battery packs to be added by an ROV to Sonardyne data loggers, enabling them to meet the widest range of downhole monitoring needs.

 4 SMART

Subsea Monitoring, Analysis and Reporting TechnologyOne of the limitations of acoustic monitoring systems is the restricted bandwidth of the data link. That being said, great strides have been made with the last two generations of Sonardyne product, evolving them to a point where user data rates can now be as high as 9,000 bps with reliable connections.

However, the fundamental physics of the acoustic channel means that further advances in data rate will be limited. The addition of new platforms such as BlueComm are one way of overcoming this constraint, along with Sonardyne continuously working on ways of making that limited channel work harder, or we could say ‘smarter’ for their customers.

Part of that continuous development is the Subsea Monitoring, Analysis and Reporting Technology or SMART unit. A new development from Sonardyne, the unit builds on the 6G instrument platform but adds a new layer of data processing to enable more intelligent subsea systems. SMART is a flexible platform which can be outfitted with a wide range of internal sensors including pressure, temperature, inclinometers and accelerometers, to name just a few. It is also capable of interfacing to external sensors (digital and analogue) such as chemical sniffers, strain gauges and Doppler current profilers.

Where SMART is different is that the functionality doesn’t stop at secure logging. With redundant storage of sensor data, information can be processed within the unit to produce summary data from simple statistical averages through frequency domain analysis, to more sophisticated processing using complex algorithms. These can either be created by Sonardyne or provided by customers. The summary data can then be transmitted at regular intervals to a topside system giving the customer near real-time information about the condition of whatever the SMART unit is monitoring.

The value of being able to get regular data updates, rather than waiting for periods of up to a year to get access to data from existing ROV retrievable logging units, can be significant for operators. The ability to reduce the level of conservatism applied to the design of structures, such as risers, through improved knowledge of fatigue life evolution, can result in much greater savings than the cost of the SMART units.

Other applications for SMART include pipeline commissioning and monitoring and, with its inherent flexibility, we’re still finding new places where SMART can help both existing and new customers.

“Subsea Monitoring, Analysis and Reporting Transponder – or SMART – is a new development from Sonardyne. The unit builds on the 6G instrument platform, but adds a new layer of data processing to enable more intelligent subsea systems.”

5 Automatic Integrity Monitoring 

Sentry IMS Although all care is taken to ensure that subsea oil and gas structures and assets are protected and sealed against the dangers of hydrocarbon breaches, there still exists the danger of environmental damage occurring as a result of these. That’s why early detection of small integrity breaches is vital. It prevents leaks from increasing in size and severity and allows companies to quickly take action to contain the spill, before it becomes an environmentally threatening and costly disaster.

The Sentry IMS continuously monitors for hydrocarbons around subsea oil and gas assets in more than one billion cubic feet of seawater, with 360° of coverage from a single mounted sensor location. The system is very sensitive and is capable of detecting multiphase breaches below 1 barrel per day at ranges in excess of 500 metres in deep water. All of which can be achieved without the need for skilled sonar operators to constantly monitor the system.

Sonardyne Sentry IMS functions as an active sonar by projecting a short duration, high bandwidth ultrasonic pulse into the water and listening for echoes from any objects such as subsea structures, ROVs or hydrocarbons. The advanced software in Sentry IMS is then capable of differentiating and localising a potential breach from all the other sonar targets. When such a breach is detected, Sentry IMS then automatically produces an audible and visible alarm. Data on the size and position are shown on a display and can also be exported to other monitoring or control systems via an Ethernet link.

Looking to the future

Although we’ve been extracting oil and gas offshore since the ‘70s, for much of that time we’ve had very little information about the condition and performance of the subsea equipment and structures that are part of that process. The developments that Sonardyne has been part of in the last few years, have made accessing this information a more realistic and affordable option. However, there is still a long way to go.

If we compare the oil and gas sector to comparative capital intensive industries – power generation and aerospace spring to mind – we are still playing ‘catch-up’. The latest generation of aero engines have up to 5,000 monitoring points, with data from the worldwide fleet all being analysed 24/7 by the manufacturers. With the advent of high data rate technologies such as BlueComm, and the ability to analyse data in-situ through tools such as SMART, we at Sonardyne are working with our customers to close that gap.

The potential benefits are great; longer equipment life, higher production rates and reduced intervention costs, all of which contribute to the bottom line. Monitoring makes sense, subsea, as much as it does in the sky!