Testing times for subsea and downhole equipment

Jon Lawson

Dr Carl Wordsworth reveals why, today more than ever, onshore testing is vital for equipment destined for subsea environments

With our energy requirements set to increase in the years to come and oilfields becoming increasingly less accessible, plans have been put into place to drill ultra-deep wells.

Consequently, the reliability and long service life of subsea and downhole equipment is vital to the success of the oil and gas sector as it can be extremely costly to repair and maintain.

Intervention – where it is even possible – frequently involves the mobilisation of highly-specialised technologies and equipment, and often has a considerable impact on production and costs.

Handling pressure depth and flow assurance

Firms operating in the UK Continental Shelf (UKCS) are working at ever increasing depths, plus there is a growing industry trend towards exploiting subsea resources in West Africa, the Caspian Sea and the arctic. With increased depth comes increased risk of components failing. As a result, equipment manufacturers are currently expected to prepare their products for depths of between 1,000 and 1,500m, where the absolute atmospheric pressures at this depth range from approximately 102 to 151 bar.

However, it is likely that we could see operators asking designers for equipment that can perform at depths of 3,000m in as little as five years’ time. This will see a tripling of the pressure that parts must be capable of handling while still performing optimally. In fact, it has been suggested that subsea operations might see depths of 5,000m to 6,000m become the norm. At this depth the pressure becomes the equivalent to instruments holding the weight of a horse on every square centimetre, making it clear that there is very little room for error.

Furthermore, depth can lead to major changes to the oil itself, which impacts the ability to regulate it and transport it to the surface. Many subsea operators will work within the thermocline, which means that most sea bed temperatures sit between 3 to 4°C. However, the ranges between sea bed and surface temperatures, for example in North Africa and the Caspian, might be very different. Thus, equipment must be able to withstand expansion and contraction from these temperature changes. Pipeline insulation companies perform crucial tests to ensure that pipes and equipment can maintain the temperature of oil for as long as 10 to 12 hours.

Navigating the TRL

In considering the risks relating to depth, there is a clear need for regulation in this sector. One such piece of regulation is the seven level Technology Readiness Level (API 17N) that manufacturers must assure their components are put through as a necessary measure to avoid production issues, and more importantly, to prevent environmental disaster. However, navigating it can be a drain on resources and testing costs increase considerably through the stages.  As a result, many designers can handle the simulated computer modelling of components at the early stages, but struggle when it comes to the rigorous field testing of full scale prototypes occurring in the latter stages.

The most important stages of TRL begin at level four and five where full-scale prototypes are evaluated within an intended simulated or actual environment often with full interface and functionality tests. Replicating the downhole conditions that equipment will see in the field is not easy. Manufacturers typically use computer simulations or modelling rather than physical testing. This carries its own inherent risks, where unforeseen ‘real-life’ conditions are not factored into the models. Also the computer simulation of multiphase flows is often simplistic at best, and often requires physical testing to validate the computer models developed. Manufacturers often use computer modelling until a very late testing stage. They also often use expensive competitor owned testing facilities, which means that results and testing time can be hard to obtain.

What equipment manufacturers need is an independent downhole test facility, onshore and with the ability to replicate a variety of real life conditions. For equipment manufacturers that need to evaluate prototypes at stage four and five of TRL, having access to these test facilities will not only lower costs but also help prove designs more quickly and easily than before.

What to look for in a testing facility 

Due to increasing demand, such testing facilities are beginning to open in the UK. Some facilities currently available have the capacity to simulate as much as 40bar at the base of the well and can simulate a 400m fluid depth with representative well conditions for development, performance and reliability testing of components and systems.

For some equipment it is important to be able to test with a variety of fluids in single or multiphase flow at elevated pressure and temperature for extended durations. Furthermore the capacity to incorporate accurate, high speed measurements of downhole pressure, temperature and flow is crucial to ensure that product performance can be mapped over a range of conditions.

Often facilities have CCTV that can be accessed via VPNs, enabling round-the-clock monitoring without the need to be at the facility in person. It is also crucial that conditions are entirely customisable in order for companies to meet specific technical requirements to meet national, international or industry standards. In addition, it is key that manufacturers use facilities managed by open innovation experts that are able to use their multidisciplinary experience in areas such as pumps, jet pumps, separators and instrumentation to understand which technologies will scale and bring the most business benefit and cost savings.

These facilities have seen great success working with companies producing equipment such as pipeline insulation for ultra-deep subsea conditions. For example, it is possible for a section of pipeline and insulation to be put under simulated conditions, and OHTC testing capabilities allow companies to validate previous heat transfer models, giving them great insights into the thermal properties of their products.  This has allowed them to build to scale and move forward with developing the technology for field deployment.

Future proofing as we move towards greater depths

From an environmental and production standpoint, testing is crucial to ensure that components can withstand the intense pressures of subsea environments.  With production companies seeking to exploit resources in deeper waters, equipment needs to be tested under current conditions and also with the foresight that it is likely to be deployed at far deeper depths in the future. Onshore downhole test facilities have the ability to replicate these conditions in a controlled and realistic manner allowing manufacturers to see how their equipment stands up during product development. Furthermore, equipment manufacturers can vastly reduce the cost of research and development by ensuring that they navigate the TRL treadmill through regular testing.

Particularly in the oil and gas field, the ability to work with independent fluid engineering experts and downhole testing facilities, which provide full visibility into testing and results, will deliver firms the accurate intelligence they need to progress their products into the final stages of testing.

There is certainly a case for more robust and accurate testing of equipment destined for the most extreme subsea environments. If production firms plan to go deeper than they have before, they need the highest levels of equipment and product innovation to deal with the ever-increasing pressure and temperature issues on the seabed.

Dr Carl Wordsworth is senior consultant at BHR Group. 

Advanced downhole test facility

One recently opened downhole test facility, in Cranfield, Bedfordshire, provides companies with an easily-accessible, onshore facility that accurately reproduces downhole conditions to economically achieve test objectives.

With the capacity to achieve 40 bar at the base of the well, BHR’s facility can simulate a 400m fluid depth with representative well conditions for development, performance and reliability testing of components and systems. It is able to test with a variety of fluids in single or multiphase flow at elevated pressure and temperature for extended durations.

The facility incorporates accurate, high speed measurements of downhole pressure, temperature and flow ensuring that product performance can be mapped under a range of conditions and providing a comprehensive equipment testing capability.

The facility can be used for product development and qualification testing / type approval of downhole equipment, such as: pumping equipment; jet pumps; separators; instrumentation; and drilling fluids.

New deep-water test tank launched

Subsea technology provider Forum Energy Technologies has unveiled a deep-water test facility and received industry accreditation for the calibration laboratory at its new European Operational Centre in Aberdeen.

The indoor test tank is one of the largest in the North-east of Scotland and is dedicated to testing subsea tooling and survey sensors as well as work-class remotely operated vehicles (ROVs).

Staffed by dedicated personnel, the test tank and laboratory have a primary purpose to provide full control, certification and faster turnaround in preparing Forum’s rental inventory for hire. In addition, the firm will also offer a full test and calibration service to customers.

Ian Porter, VP for Manufacturing Subsea, says: “Our continued investment in testing and calibration capabilities ensures that clients can be assured our systems have been prepared to the highest possible standards. This focus on delivering quality products means clients know they are receiving ROV systems that will perform reliably in the field and safeguard the project costs.”

The large fresh water tank, measuring 5m x 6m x 4.5m, is fitted with overhead 10T crane, lighting, cameras and a viewing platform.

The calibration laboratory has been accredited by Valeport and conforms to traceable procedures for the recalibration of Valeport CTDs (conductivity, temperature and density) and Sound Velocity sensors and parameters fitted on current meters, tide gauges, wave recorders and loggers.

In addition, seven of Forum Subsea Rentals’ (FSR) engineers have undergone extensive training at Valeport on all aspects of the calibration of CTD and Sound Velocity parameters. 

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