Overview of FeS Scale Control and Treatment Under Challenging Applications

Abstract

Iron sulfide (FeS) scale is a well-known troublesome solid during oil and gas production for causing plugging, emulsion, and other production upset issues. It can be found in various systems, including injection wells, production wells, surface facilities, and saltwater disposal wells (SWD). While iron sulfide is challenging to control, several main management approaches include: (i) inhibition of FeS formation with scale inhibitors; (ii) dispersion into finer particles by dispersants; (iii) sequestering iron with chelators to mitigate precipitation; (iv) dissolution of existing FeS deposits by acids, e.g., hydrochloric acid (HCl) or citric acid. Each of these approaches has limitations and should typically be combined with the implementation of corrosion inhibitors to reduce iron sources and H2S scavengers to control H2S levels in brines to achieve successful FeS deposition control. In this paper we review common treatment approaches in different application systems, including production wells, saltwater disposal wells, and surface facilities, and present case histories of FeS treatment by acids and chelators e.g., THPS (Tetrakis Hydroxymethyl Phosphonium Sulfate). The pros and cons of chemical treatment programs are explored, and effective treatment approaches and strategies will be compared and discussed. This paper's overview of current treatment approaches provides insight into the impacts of FeS deposition control in various applications and shares valuable best practices from case histories to aid in successful FeS scale management in future operations.