Comparing Efficacy of Scale Inhibitors for Inhibition of Zinc Sulfide and Lead Sulfide Scales.

Abstract

Abstract A large independent operator in Mobile Bay, Gulf of Mexico was experiencing a buildup of common and exotic scales where the produced waters are commingled. The scale species encountered included barium sulfate, zinc sulfide, and lead sulfide. Traditionally, scale inhibitor chemistries have not been used in the past to inhibit these exotic sulfide scales in this region. This is due to some amount of belief within the industry that conventional inhibitors alone could not inhibit these scale species. Prior to the application of the scale inhibitor in the field, the platform's overboard water line required cleanout every two months due to scale buildup. Not a single cleanout has been necessary since a polymeric scale inhibitor has been applied downhole via continuous capillary injection for over one year. This paper presents the results of laboratory tests which were used to demonstrate how a polymeric scale inhibitor was identified and approved for inhibition of lead sulfide and iron sulfide, as well as the more common scales. The sulfide scale tests performed in an anaerobic dynamic tube-blocking test unit showed this inhibitor chemistry to be as effective as combined scale inhibitor/dispersant products. The paper then presents the field treatment results, which shows good agreement with the lab test results.