Review of Iron Sulfide Scale: The Facts & Developments and Relation to Oil and Gas Production

Abstract Oilfield iron sulfide (FeS) control and prevention have been mostly proprietary with several disparate solutions. Frequently FeS control involves milling, jetting, acid soaking, pulling and replacing tubing and manually cleaning tanks, vessels, separators and pumps. These methods are costly, wasteful and strenuous. This paper reviews the latest developments in oilfield FeS researches with an attempt to integrate viable solutions and expose unworkable practices. In this work, we review and evaluate the most common FeS prevention and control solutions in an attempt to summarize the state-of-art FeS mitigation technologies. We have a closer look on FeS formation and control as well as potential integrated solutions. The paper reviews and differentiates treatment solutions between corrosion byproduct and FeS scale deposition from formation. Most FeS scales have generally been treated as the same, using various treatment methods. Complex FeS polymorphs have resulted in different outcomes. This work focuses on different treatment options that assert to work for all FeS scale not differentiating between corrosion-byproduct and reservoir formed scale. Successful case histories and suspected FeS polymorph are presented in this paper next to discussion of the model used to predict severity of the deposition and analyze the treatment design. FeS formation and deposition is evaluated, especially crystallography and fundamental studies into mechanistic aspects of FeS precipitation and how it relates to oilfield FeS precipitation. In this paper state-of-art FeS scale research is summarized and differences to normal scale types are presented. Mineral scale in the true sense of going through the stages of nucleation, pre-crystallization, crystal growth, agglomeration and deposition. This is an important step change in consolidating all the disparate areas of FeS studies into an advanced solution focused approach. If FeS scale is considered a mineral scale then solutions such as scale inhibitor applications (continuous injection and squeeze) that work for common mineral scales should work for FeS deposition as well. Thereby moving FeS research from a relatively empirical level with vastly different approaches that are mostly unrealistic into solutions that will be viable in the oilfield.