Mechanisms and Mitigation Strategies of Iron Sulfide Deposition in Sour Gas Wells

Iron sulfide deposition on downhole tubular is a ubiquitous phenomenon in sour gas wells, especially for these producing from high temperature and high pressure (HTHP) reservoirs. Many studies have been focused on iron sulfide formation and mitigation previously, the root-cause of iron sulfide deposition is still not well defined and the cost-effective scale management strategy is remained to be identified. This paper presents some new progresses made for understanding the mechanisms of iron sulfide deposition in the sour gas wells, using a combined approach of laboratorial tests and model prediction. Study results indicate that iron sulfide can deposit during both acidizing treatment and production stage. Large amount of iron sulfide could precipitate during acidizing treatment and potentially causes severe formation damage. During production stage iron sulfide is accumulated on tubular surface due to corrosion of the underlying metal. This paper presents a fundamental study to understand the mechanisms of iron sulfide deposition in sour gas wells. Corrosion and scaling inhibition are recommended to mitigate iron sulfide deposition in sour gas wells, especially during acidizing treatment.