Recent Development and Remaining Challenges of Iron Sulfide Scale Mitigation in Sour Gas Wells

Iron sulfide scale deposition can be a significant flow assurance issue in the sour gas production systems. It can deposit along the water flowing path from near wellbore reservoir area to surface equipment, which results in formation damage, causes tubing blockage, interferes with well intervention, and reduces hydrocarbon production. The main objectives of this paper are to review on the new advancements and remaining challenges of iron sulfide scale management in sour gas wells, covering the mechanisms of iron sulfide formation; the mechanical and chemical removal techniques; and the prevention strategies. This paper gives a special emphasis to the different mechanisms of iron sulfide formation during well completion and production stages, especially the sources of ferrous iron for scale deposition. It is essential to understand the root-cause in order to identify and develop suitable technologies to manage the scale problem. The paper also summarizes the latest developments in mechanical methods and chemical dissolvers for the removal of iron sulfide deposited on downhole tubing. The capabilities of the current chemical dissolvers is discussed and the criteria of effective dissolvers are provided to serve as a guide for future development. Then the paper provides an overview of recent developments on iron sulfide prevention technologies and treatment strategies. It differentiates the treatment approaches for corrosion byproduct and scale precipitation and scale inhibitor deployment through continuous injection and squeeze treatment. Finally, the paper outlines the technical gaps and areas for further research and development efforts. This paper provides the latest review on irons sulfide formation and mitigation with an attempt to integrate viable solutions and expose workable practices.