An Innovative Workflow to Determine the Root Cause of FeS Scale in Sour Oil and Gas Wells

Sour gas reservoirs are well known for causing scaling issues of Fe-sulphides that can severely hamper production. Fe-sulphide scaling can have a range of root causes, each related to a different mechanism and source of iron and sulphur. We have developed a generic workflow that covers methodology for an investigation for a broad range of possible causes of Fe-sulphide formation and applied it to a case study in the Middle East. The workflow includes data and sample collection, geochemical analyses (XRD, SEM-EDX, ICP-MS, Fe and S isotopes), flow and thermodynamic modelling. The results revealed that under the given physico-chemical conditions spent stimulation fluids and production water reflux can lead to severe scaling over time, whereas corrosion related scaling was largely absent.