Abstract

Production of mature oil and gas fields often requires managing the related risks and limitations imposed by reservoir souring upon assets and production integrity. The corrosive effect of H2S in combination with export gas H2S specifications, escalates operational expenditure (OPEX). The treatment of produced fluids can, in a worst-case scenario, reduce production output if the appropriate toolbox for managing elevated H2S levels are not in place. Herein presented is a case where production from a subsea field was restricted by the amount of H2S produced due to constrains in the topside gas processing system. The objective of the work was to remove significant amounts of H2S from produced fluids during transit via subsea production pipelines; scavenging H2S during multiphase flow, whilst maintaining corrosion and scale inhibition.

A novel multiphase H2S scavenger was incorporated into the incumbent subsea corrosion inhibitor. The work included identification of suitable multiphase H2S scavenging chemistry, tailoring of the multipurpose chemical to retain corrosion inhibition properties, and confirmation that this new chemistry did not deleteriously impact performance of other production chemicals used nor the production process itself. The experimental development work depicted ethylenedioxy(dimethanol) (EDDM) as capable of delivering suitable H2S scavenging capacity while maintaining corrosion inhibitor component performance. The qualification work supported a full-scale field test that demonstrated suitability of the new multipurpose chemical.

The new environmentally acceptable combined formulation of corrosion inhibitor and H2S scavenger enables higher production rates from the subsea field without modification of the chemical injection system or topside process system.

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