Enhanced Scale-Inhibitor Treatments With the Addition of Zinc

Summary This paper discusses research on scale inhibition and squeeze performance in the presence of Zn2+. Some scale inhibitors, such as bis-hexamethylenetriamine penta(phosphonic acid), BHPMP, and polymeric inhibitors, such as phosphinopolycarboxylate (PPCA), have poor retention characteristics in conventional squeeze treatment, where less than 50% of the inhibitor is retained in the formation. In this study, it was demonstrated that more than 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 with certain amino-pentaphosphonate scale inhibitors [BHPMP and diethylenetrimine pentaphophonic acid (DTPMP)]. Stronger solution complexes are observed for aminophosphonates type scale inhibitors with Zn2+ than that with alkaline earth metal ions, such as Ca2+, Mg2+, and Ba2+. This stronger solution complex formation with Zn2+ may be attributed to the observed enhanced inhibition efficiency. Because of the lower solubility of Zn2+-scale inhibitor salts, Zn2+ added to the inhibitor pill significantly improves 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 PSL for BHPMP is increased by a factor of 60 without significantly affecting the cost. Simulation indicates that the squeeze life may be improved significantly at the Guerra well if this new squeeze procedure is used.