Synthesis and performance evaluation of poly (acrylamide-co-malonic acid) as FeS scale inhibitor: experimental and theoretical investigations

Abstract

This article reports on poly (acrylamide-co-malonic acid) and poly(AM-co-MAc) copolymers that inhibit the iron sulfide scale. The iron sulfide scale is considered as one of the most challenging oilfield scales to dissolve or inhibit once formed due to the fast deposition kinetics and low solubility criteria. We present the synthesis, characterization, and testing of poly(AM-co-MAc) that inhibits iron sulfide formation by hindering nucleation growth and preventing particles from settling. A strictly anoxic apparatus was designed and used to evaluate the performance of the synthesized inhibitor. The influence of temperature, pH, and brine composition was also quantified. The results indicated that poly(AM-co-MAc) inhibits iron sulfide formation and nucleation growth under various conditions. The inhibitor effectively maintained iron sulfide particle separation at specific dosages, lowering its ability to cluster. Maximum efficiency of 92% was recorded at 60 °C and 1% volume inhibitor concentration. DFT calculations confirmed the inhibitive properties of poly(AM-co-MAc) via binding energy calculations. Compared to recently reported inhibitors, poly(AM-co-MAc) proves to be safer concerning toxicity properties. This study provides theoretical and technical insights for a novel chemistry solution for the metal-sulfide scale.