Iron Sulfide Chemical Dissolver Deployment in Water Wells

Abstract

Abstract This paper will introduce a pioneering Iron Sulfide (FeS) chemical dissolver. The novel chemical dissolver can be used for descaling applications in oil and gas wells. However, the particular scope of this paper would be to outline an operational well intervention workflow for a successful deployment of FeS dissolver in water wells. Iron sulfide scale presence in the wellbore is challenging to oilfield operators. Unlike other common scale types, such as Calcium Carbonates, FeS scale does not dissolve easily in Hydrochloric Acid (HCl) and the FeS/HCl reaction produces the dangerous Hydrogen Sulfide as a reaction product. Accordingly, oilfield operators resort to mechanical descaling of the FeS in order to restore wellbore accessibility. Mechanical descaling has disadvantages that include high cost, the need to flowback downhole milling returns, and possible damage to downhole tubulars. Alternatively, the novel chemical described in this paper can be used to effectively descale the wellbore without exposing the oilfield operator to the setbacks that could encountered from mechanical descaling. This paper will outline operational steps to execute a flagship descaling operation. The operational steps include pre-job diagnostics, job design and contingencies, as well as expected results and outcomes. The proposed FeS dissolving chemical has successfully met all laboratory and field criteria to descale iron sulfide scale and stimulated well injectivity. The deployment of the FeS dissolver can result in 67 % increase in overall well injection rate compared to pre-chemical descaling rate. Other tangible benefits to this chemical include avoidance of rig workover operations to pull and replace downhole tubing in cases where mechanical descaling was not successful in restoring wellbore access. The new chemical allows for conducting safer descaling operation by reducing risks associated with reproduction of hydrogen sulfide, formation damage from non-friendly chemicals, and downhole equipment damage by corrosion. The chemical also has the ability to dissolve carbonates for near wellbore cleanup. The dissolver has a 70 % enhanced dissolving ability comparing to 15% HCl.