Extending umbilical life

Neil Douglas

January 16, 2014

Viper Subsea’s V-LIFE is increasing insulation resistance to extend subsea systems’ life expectancy.

It is well understood that water and electricity don’t mix well. Since the advent of electro-hydraulic control systems, this fact has presented an ongoing challenge to subsea engineers as they try to ensure electrical conductors within cables and connectors are kept dry for the design life of subsea production systems.

Design, quality, manufacturing, and test processes have improved over time. However, the industry still has to work with the legacy of installed equipment that was designed and manufactured some time ago. If sea water penetrates electrical insulation barriers, operators face an expensive problem, as well as a potential safety issue.

The introduction of sea water into the electrical cables and connectors causes a reduction in insulation resistance (IR), which nearly always continues to deteriorate to a point where a complete failure occurs. Such a failure could potentially lead to loss of production.

Seabed-based components form part of the subsea distribution system susceptible to water ingress, include subsea umbilicals, distribution units, electrical connectors, and flying leads. All of these are used to transport electrical power and communication signals from a surface facility to the subsea production equipment.

Along with the potential loss of production, failing insulation resistance can also mean extra electrical hazards for technicians working on topside electrical power units.

Previously, in the event that sea water penetrated electrical cables, there was no alternative to a costly subsea intervention to fault find and replace failing equipment.

Viper Subsea has been working on a solution to overcome the effect of water penetration. V-LIFE uses a combination of dynamic electro-kinetic and electrochemical processes to reverse the effect of water penetration into or through electrical insulation material. It is connected to the umbilical at the topsides only, which means installation requires no subsea intervention.

The outcome is an increase in the insulation resistance of electrical distribution components, which increases life expectancy on failing equipment.

V-LIFE is designed to be compatible with all ageing and new subsea production control systems, including those operating with both separate power and communications networks, and systems where communications are superim- posed on the power.

The V-LIFE unit automatically logs various system electrical parameters and diagnostic data, with accurate real time IR measurements, down to <1Kohm, and line current and voltage measurements.

To maintain their efficiency, data from the units is periodically analyzed, and configuration updates carried out on the installed units.

V-LIFE underwent a field trial on a North Sea field with known IR problems. The field trial started in July 2012, and the IR was increased from less than 50kΩ to 25MΩ in less than two months.

The unit remains operational, with the IR being kept at a high level and has been independently verified.

Centrica Energy’s exploration and production business was one of the first companies to commercially use V-LIFE. Centrica’s Birch, Larch and Sycamore wells, located in the UK North Sea, are all tied back to the Brae Alpha platform via a single subsea umbilical. These had been shut-in, having experienced some electrical power problems with the control system.

Centrica used V-LIFE to improve the electrical insulation on the umbilical. The IR has been increased by a factor of more than 200. This increase avoided the need to procure and install a new umbilical. Production has since increased from the Birch and Sycamore Fields and safety has been improved.

V-LIFE has since been adopted by a number of other North Sea operators to extend subsea equipment life expectancy, postpone early field abandonment, negate the need to install new umbilicals, or to increase technical margins to improve operability and safe working of production control systems.

To date, it has a 100% success rate in increasing IR.

Details of the exact technique used remains confidential, as patent is pending and has not yet been published. V-LIFE has been verified by an independent UK University. OE

Neil Douglas is the founder and manag- ing director of Viper Subsea. He graduated with an electronics degree from Bristol University before joining GEC Marconi. He served as global technical director for GE Oil & Gas before leaving to co-found Viper Subsea in 2007.