As subsea systems become more complex, both installation and life of asset management become challenging. Alistair Birnie looks at Ashtead Technology’s development of an advanced suite of common integrated building blocks to support subsea construction and integrity management with key examples: suction piled structures, mono-piles, wind turbines and jacket installations and fatigue monitoring applications.
Subsea construction and life-of-asset integrity management are increasingly dependent upon high levels of complex instrumentation, data management and processing systems.
“Big data” is increasingly recognized by the exploration and production community as a means of maximizing performance and end clients recognize the need for reliable mass data acquisition that can be easily interpreted from initial construction through life of field to decommissioning.
But “big data” has a cost and that is where things start to go wrong, particularly when taking specific applications in isolation. The default position has led to many different bespoke packages being designed over and over again, all trying to deal with similar issues, all with common problems but some differences.
These bespoke solutions have caused project difficulties contributing to associated loss of data, delay, cost over-run, with lost production and hydrocarbon emissions potential.
Operators recognize the specialist nature of systems integration and the difficulty in hiring and retaining professionals in these fields and have increasingly pushed the integration of subsea monitoring systems out to sub-contractors with the result that today’s technology for subsea construction and integrity monitoring is stretched to its limit and lacks scalability and fully integrated solutions that can deliver on “big data” demands.
The lower, for longer oil price environment has forced the industry to re-think many aspects of actual and risk costs which, in turn, drives the re-thinking of how subsea operations and critical monitoring information are gathered.
Ashtead Technology’s Philosophy
Being a specialist solutions provider in subsea construction, integrity and IRM systems, Ashtead has recognized the need to simplify the integration of sensor packages and to provide integrated monitoring and sensing systems based on common proven building blocks.
Where feasible, these building blocks should be common across all subsea monitoring applications and be capable of being configured to accept virtually any sensor permutation, provide a subsea processing platform to rationalize and store data as appropriate, communicate to the surface and to calibrate, process and present the output information at the surface. This allows for easy and reliable interpretation of data to log and pass on to third parties.
Our advanced suite of integrated subsea monitoring and data systems are based on the following:
The approach has been to standardize instrumentation integration methodologies and to develop common building blocks that are integrated using simple and robust physical interfaces and software tools that are re-used across diverse applications to reduce integration risk and the time taken to configure and test these.
This takes into account how data is transformed into valuable information and how the information is likely to be used to inform decisions both in real time and in a historic context.
At the heart of Ashtead’s philosophy is a flexible core system that provides multi-channel communications and data management capabilities, built using common building blocks within an industry-standard environment.
This allows flexible configuration and connection of systems using the core system that has already been proven and deployed, which reduces significantly the amount of bespoke development and associated risk whilst reducing the time to respond to specific needs.
The level of connectivity that the Ashtead core system provides within a common software and hardware framework, allows simplified selection of a wide range of connection options to suit specific configuration needs and to allow scalability from the simplest to most complex of operations.
Using its common core building blocks, Ashtead has successfully deployed a range of applications with varying degrees of complexity, providing vital data during subsea construction and life of asset operations.
These applications use common hardware, software and systems integration methodologies to integrate gyro packages, depth gauges, inclinometers and other sensors to provide autonomous packages that can be deployed, used and retrieved by both divers and ROV systems.
Attitude Monitoring System (AMS)
This is a widely used tool for subsea structure installation and orientation. It has been used on subsea manifold, template, suction pile, wind turbine pile and flow-line applications to provide orientation and attitude information and can be configured to operate either autonomously by divers or via acoustic control and monitoring systems.
The system has been successfully integrated with LBL and USBL positioning networks including Sonardyne Mk5 and 6GCompatts via both ROVNav and Dunking transceivers, Compatt C-Nodes via vessel HiPap and autonomous Benthos acoustic modems, allowing highly flexible integration to existing construction and IRM support acoustic networks.
Simple to use, in-built functions provide a significant improvement in operability and powerful capabilities that can significantly improve safety as well as reducing survey time.
In addition to utilizing the communications capabilities to acquire data, the AMS system can also be remotely controlled to put the system to sleep and wake up, allowing effective power management and battery optimization.
All AMS systems can undertake all the dimensional controls observations remotely via an in-built RF link. Using this function, the surveyor can do all the required calibrations including downloading of latitude of the fabrication yard and then the deployment location to the gyro without having to physically climb onto the structure.
This RF control link also provides the ability to remotely control the system to allow it to sleep until the structure is being launched, at which time it can be awakened using a hand-held radio controller.
The Ashtead AMS system also provides visual output of gyro and battery information via subsea visual displays allowing both stand-alone diver operation and ROV monitoring in the event that an acoustic link is not available.
Where applications require extended autonomy for complex tow-out and installation, the AMS system has been configured to provide long-term deployment, using identical systems to those for the base system.
This system was deployed offshore Brazil to support the buoyancy modules for the buoyancy supported riser packages and included monitoring of depth position, structure heading and attitude.
In addition to acoustic data control and data communication this system employed a hard-wired connection system between the construction vessel and the AMS.
Deflection Monitoring System (DMS)
The DMS extends the use of common building blocks and interfaces further by providing real-time monitoring capabilities for suction pile installed structures.
The suction pile relative depths are monitored at each of the four corners of the structure and are integrated into a common data stream via the same communications and management hub used on the AMS system.
In addition to measurement of depth at each of the piles, the differential pressure is also monitored in real time to provide feedback of the pressure to avoid collapse of the suction piles in the event of excessive force being encountered during pile insertion.
Ashtead’s DMS supports acoustic telemetry via Kongsberg C-Node and HiPap, Sonardyne 6G data Transponder and Benthos 926 series Modem and most other transparent modems may also be utilized. WFS short range subsea radio telemetry can also be used as a subsea communications medium
The DMS has an ROV wet mateable connector channel that can provide direct communication between the subsea system and surface via the ROV communication system which also provides a power feed, should this be required.
The DMS is also capable of providing fully segregated dual independent control and communications, allowing continued seamless operation in the event of a complete system failure.
As with the AMS system, the DMS also supports surface RF communications, allowing dimensional control and structure launch management to be controlled and monitored fully remotely.
As Ashtead’s DMS has been built upon a scalable platform using common blocks, extending the system to more complex configurations is easy, and does not require re-engineering of the system or components.
In the same way that the Ashtead family of subsea monitoring systems uses common building blocks, so does the surface control and monitoring software.
Using a series of common software library blocks and functions to provide communications, display management, data logging and visualization, allows rapid application configuration to match specific client needs in terms of data connectivity, local logging support as well as presentation of data.
Vibration Monitoring System application (VMS)
This technology extends further to integrity monitoring applications where vortex induced vibration measurement, storage and data retrieval may be required.
The monitoring requirement may be temporary for a short period, e.g. in verification of riser vibration modes, or it may be longer term, e.g. in monitoring the stability of a pipeline free-span region. This may be required in the case of seasonal currents that can induce seasonal fatigue issues.
In the case of short-term monitoring, the data is collated and stored in local memory at the sensor, and it can be downloaded after the observations have been completed.
For longer-term monitoring, it may be necessary to provide an extended battery autonomy and to correlate water current speed and direction and turbulence with the vibration measurements.
The structure of the system utilities the same building blocks as the AMS and DMS systems, reducing risk and ensuring maximum supportability for specific applications.
A step-change is essential within life of asset integrity monitoring systems to improve reliability of data and reduce overall operational costs, whilst increasing efficiency through reduced vessel time and eliminating unnecessary safety risks. This is further driven by contractors changing the way they do business, focusing on their core competencies and requiring subcontractors to provide supporting services.
By adopting a fresh mind-set, Ashtead has developed this rapidly configurable system architecture that can handle a wide range of applications without having to re-engineer on a project by project basis, allowing a faster, commercially competitive and significantly lower risk response to client needs.
Using a building-block philosophy, the flexible core system provides multi-channel communications and data management capabilities. This common data systems application framework delivers precise monitoring of subsea construction, integrity and data integration operations. By creating these effective, easily integrated building-blocks, the system can be used from initial installation through life-of-field support and eventual decommissioning.
Alistair Birnie is a Chartered Engineer and graduate of University of Aberdeen and RGU. Alistair worked for many years in senior roles in subsea before taking the role of CEO of Subsea UK in 2008. In 2011 he took the role of Professor of Subsea Engineering NUS and has worked closely with Ashtead Technology supporting development of new technologies.
Ashtead Technologies was recently acquired by Buckthorn Partners and the Arab Petroleum Investments Corp.
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