Join OEdigital on Facebook Join OEdigital on LinkedIn Join OEdigital on Twitter
 

Weighing the options

Written by  Joao Melo, Oceaneering Wednesday, 01 November 2017 00:00

Oceaneering’s Joao Melo explains how operators can decide if aged assets can live longer. 

Umbilicals and termination assemblies ready for testing. Images from Oceeaneering.

Subsea umbilicals are critical components in most subsea oil and gas production infrastructure, connecting topside facilities to subsea equipment and interconnecting them as required. Through these connections, hydraulic and electrical power, electrical/optical signals and chemicals are supplied to the system. While typically designed for 15-25 years’ operational life, in many situations the actual field life is longer. This forces operators to assess their options, i.e.:

  • Do nothing and accept the risk of a failure during operation;
  • Purchase sufficient spares to maintain operation of the existing equipment (not always a viable alternative for umbilicals and some of their failure modes);
  • Replace or upgrade parts of the equipment (again, not always a viable alternative for umbilicals and some of their failure modes);
  • Replace or upgrade the equipment.

In recent years, Oceaneering has been involved in the assessment of the risks related to a potential decision to extend the life of aged umbilicals for various operators and relating to different fields, applications and environments. The process used for such assessment includes a detailed review of all available information regarding the asset (including design, manufacturing, installation and operational data), the identification of risks based on the analysis of the information available (or the lack of information available) and the assessment of each risk identified, based on its likelihood of occurrence and impact (on safety, the environment, quality or cost).

One common mistake made during these types of studies is to focus on – and to put a majority of resources into – one single area of concern (such as on the most evident or most recent risks identified, based on previous experiences from the individuals involved in the decision-making process). Although this usually addresses real and critical risks, it could, and most certainly will, take focus away from other areas and risks that might ultimately lead to different decisions (such as a decision to replace the asset). In other words, the best practice is to identify and assess all risks before making any decisions and taking action.

Assessing risk

Some of the most common high-risk areas identified in our analysis include:

Compatibility with operational fluids: Particularly with, but not limited to, umbilicals that use thermoplastic hoses as hydraulic conduits, the long-term compatibility between the operational fluids (or combinations of fluids) should be confirmed. It is very likely that different fluids would have been used over the years and may not have been tested against the materials in question – and could, therefore, slowly deteriorate the hydraulic lines’ performance, leading to complete loss of functionality. Scenarios where the fluid within a given hose is “unknown” have been reported before, but should (of course) be avoided.

Fatigue: This is normally one of the areas of focus for dynamic applications. Concerns regarding the fatigue life of metallic elements of the umbilical (steel wires, tubes and/or copper conductors) include assessing the increased risk of catastrophic failure, along with confirming that the necessary design criteria defined by applicable standards will continue to be met in case of life extension. Advances in design tools and the increased availability of environmental information could also be drivers for reassessing a product’s fatigue performance.

Corrosion: Corrosion is most certainly a risk that will need to be assessed. The effects on unprotected elements including steel tubes, for example, to corrosive environments and the evaluation of cathodic protection systems having a defined design life and may need to be resized accordingly to support a life extension scenario must also be considered.

Other high-risk areas include certain design aspects of ancillary items within the system (often resulting from a lack of evidence that the adequate engineering has been done to validate the designs), as well as the obsolescence of products originally used.

Umbilical assembly ready for load-out.

Data management

As we are faced with decisions regarding the life extension of assets (umbilicals, in particular), it is important to identify areas where we should adjust our processes and products today to help those who will be faced with similar questions and challenges in years to come. What can we do today to better support a decision-making process that will take place 20-30 years from now?

The entire risk identification and assessment exercise is based on available information regarding the asset. One thing we are learning is that, despite all the efforts that our industry puts on generating good documentation and traceability, if this information is not maintained and readily accessible when needed, then all such efforts would have been in vain. Data management systems that consolidate all the relevant documentation regarding an asset should be put in place and used across the entire life cycle.

Having accurate information on how a product performs in the field, including what levels of stresses have been imposed on it, would allow companies to compare that information with design models and identify opportunities to extend the product’s operational life. Decisions made based on actual data, rather than estimated or theoretical figures, would certainly enable better and less conservative decisions.  

About the author

Joao Melo is a mechanical engineer with over 15 years of industry experience, mostly in the umbilicals, subsea connection, and distribution business. He has held positions in engineering, project management, and technical sales, and now works as the Engineering Manager for Oceaneering - Subsea Distribution Solutions in the UK.

 
Read 2191 times