Optimising Flow Assurance Strategies in an Offshore Sandstone Oil Field with Gas Hydrate Issues

Daramola, Babalola (Propellio Limited) | Alinnor, Chidubem Martins (Drilling and Completions Engineer)



This publication presents how the flow assurance strategies of a sandstone oil field were optimised after numerous production upsets. It also uses economics to justify facilities enhancement projects for flow assurance. Field F is an offshore oil field with 210 feet water depth and eight subsea wells tied back to a third party FPSO vessel.

Field F was shut down for turnaround maintenance in 2015. After the field was brought back online, one of the production wells (F5) failed to flow. An evaluation of the reservoir, well, and facilities data suggested that there was a gas hydrate blockage in the pipeline. A subsea intervention vessel was then hired to execute a pipeline pigging and clean-out operation, which removed the gas hydrate, and restored oil production from the F5 well. To minimise oil production losses due to flow assurance issues, the asset team evaluated the viability of installing a test pipeline and a second methanol umbilical as facilities enhancement projects.

The pipeline clean-out operation delivered 5400 barrels of oil per day production to the asset. The feasibility study suggested that installing a second methanol umbilical and a test pipeline are economically attractive. It is recommended that the new methanol umbilical is installed and used to guarantee flow from the F5 well and the planned infill production wells. The test pipeline should also be installed and used for new well clean ups, well testing, well sampling, water chemistry analysis, tracer evaluation, and production optimisation.

This paper presents failure diagnosis and flow assurance remediation steps in a producing oil field, and aids the justification of test pipeline and methanol umbilical capacity enhancement projects.