Enhanced Inhibitor Treatments With the Addition of Transition Metal Ions

Abstract This paper discusses the research on scale inhibition and squeeze performance in the presence of a transition metal ion, such as Zn2+. Some scale inhibitors have poor retention characteristics in conventional squeeze treatment, where less than 50% of the inhibitors are retained in the formation. In this study, it was demonstrated that over 90% of the same scale inhibitor was retained when Zn2+ was included in the squeeze formulation. Furthermore, Zn2+ showed significant synergistic effect on barite scale inhibition of certain scale inhibitors. Together with phosphonate, Zn2+ also demonstrated a synergistic effect on corrosion inhibition. Laboratory squeeze and flowback simulation and inhibitor efficiency testing under realistic oilfield condition will be discussed. The solution complexation and precipitation chemistry of common phosphonate and polymeric inhibitors with Zn2+ have also been studied. Stronger solution complexes are observed for common scale inhibitors with Zn2+ than that with alkaline earth metal ions, such as Ca2+, Mg2+, and Ba2+. This stronger solution complex formation with transition metal ions may attribute to the observed enhanced inhibition efficiency. Due to the lower solubility of the transition metal ion-scale inhibitor salts, the transition metal ions added to the inhibitor pill significantly improve the retention of some scale inhibitors during squeeze treatment. In this paper, the projected squeeze life (PSL) is defined. When Zn2+ is used in the inhibitor pill, the projected squeeze life for BHPMP is increased by a factor of 60 without significantly impact the environment and cost. Simulation indicates that the squeeze life may be improved from 110 days to 18 years at the Guerra well if this new squeeze procedure is used.