Case Study:

Pipeline & Process

Umbilical flushing for decommissioning project

Fluid Pumping, Chemical Cleaning


As part of a larger decommissioning project, a major North Sea operator required an urgent mobilisation to carry out an umbilical flushing operation. The work scope required the removal of all traces of oils and chemicals from six umbilicals at 1000m  length. In addition, it needed to be completed between dive operations. Flushing the umbilicals would enable the Client to cut the umbilicals without the risk of oil spills or chemicals entering the environment.



Altus Intervention worked closely with the Client to propose an effective solution that could be delivered within the critical timeframe. A process equipment package was quickly mobillised with an experienced and highly skilled multi-disciplined crew.  It was agreed that an initial purge with an EGMBE chemical would be used to remove all traces of hydraulic oils from the umbilicals at specific flow rates. This would then be followed with a 50/50 mix of MEG and water to remove all traces of the EGMBE chemical, again at specific flow rates. This was monitored by the use of sampling at the return side of the umbilical loop using a Densitometer. The process was completed from the topside umbilical termination unit (TUTU) down to the subsea connection and back up the return lines of two different sizes. All return fluids were captured and safely transferred to the Platform waste tanks for disposal.   



The work scope to clean the six umbilical cores was successfully completed one day ahead of schedule and the Client was subsequently able to cut the umbilicals without the risk of spillage into the sea during the decommissioning of the platform. This operation demonstrated the Process team’s proactive and “can-do” approach to get the job done and was commended by the Client.