January 27, 2021

Publication description

During 2019 the HSE requested that the OGUK Wells Forum consider whether the present arrangements for handling gas in the marine riser for UKCS operations are ALARP. It was agreed that the Wells Forum, together with the IADC North Sea Chapter, would conduct a risk assessment, separately considering deep water (over 1,000ft) and shallow water operations. The resultant risk assessment would establish the risks associated with handling gas in the marine riser on the UKCS and establish whether current mitigations are ALARP.

The assessment exercise reviewed drilling, completion, intervention and well decommissioning operations in order to:

  • Establish how hydrocarbons could be introduced into the well bore.
  • Establish how such hydrocarbons may be removed safely from the well bore using conventional well control and diverter equipment.
  • Assess the risk of introducing hydrocarbons into the marine riser and consequence when migrating to surface considering the hazards, hazard effects, population at risk, existing control measures and potential additional control measures.
  • Establish the risk of unplanned release of well bore fluids from the well bore and the associated hazards resulting from such an unplanned release.
  • Establish the relevance of water depth, if any, on the risks and outcomes.