Multifunctional Biosurfactants with Unusual pH Sensitive Interfacial Behavior for Remediation of Iron and Zinc Sulfide Formation Damage

Abstract Metal sulfide scales are found in several fields in onshore and offshore oil and gas wells around the world. Although there has been some success in the development of sulfide scale inhibitors, significantly high concentration of inhibitor is often required specially to mitigate zinc sulfide. Microbial biosurfactants have an inherent affinity towards different mineral surfaces including sulfides. The unique surface and interfacial properties of these naturally derived products make them potential candidates for development of new products for metal sulfide scale management and control. In this work the properties of sophorolipids and rhamnolipids as dispersion and modification agents for iron and zinc sulfide precipitates were investigated. Surface and interfacial tension behaviors of microbial biosurfactants were measured using a drop shape tensiometer. Accelerated dispersion stability testing were used to determine the efficiency of biosurfactants for dispersing field collected and lab-made iron and zinc sulfides. Fourier transform – infrared (FTIR) and ultraviolet – visible (UV-vis) spectroscopy was used to determine the mode of interaction of the biosurfactant active sites with metal sulfide surfaces.