Evaluation of an ENP Coating Material for Downhole Corrosion and Scale Protection in Sour Gas Wells

摘要

An advanced downhole corrosion and scale monitoring (DCSM) tool was designed and developed to effectively monitor corrosion and scaling in high temperature sour gas wells. Several exchangeable, coated metal coupons were installed on the tool to evaluate the performance of the coating material. The tool was retrieved for post-laboratory analysis after three months of exposure to reservoir conditions. The retrieved coupons were thoroughly characterized to assess the coating performance and to understand the corrosion and scaling mechanisms. X-ray diffraction (XRD) was used to analyze the composition of the coupon surface. Both scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS) analyses were performed to characterize the morphology and mineralogical changes of the coupon's surface. A surface profilometer was used to quantify the size, height, and depth of the coating surface. The results showed that a thin layer - ~90 pm in thickness - composed of nickel (Ni) and sulfur (S), was formed on the surface of the coated coupon. A slight weight loss of the coated coupon was observed, which might be due to the combination of the effects of the reaction of the coating material with hydrogen sulfide (H2S) - weight gain - and the abrasion of part of the outer layer from the surface - weight loss. Overall, the field-test demonstrated that this newly developed coating material is able to effectively protect the metal coupon against corrosion and iron sulfide (FeS) scaling. The abrasion of the formed surface layer of millerite or nickel sulfide (NiS) scale might be a concern for long-term field application.