Ultra-low Concentration Surfactants for Sandstone and Limestone Floods

Abstract

Abstract A new type of surfactant has been developed that can be used at very low concentrations to produce ultra-low interfacial tensions (IFT) for sandstone and limestone formations. These surfactants can be used for Alkaline Surfactant Polymer (ASP) floods, surfactant floods and as an adjuvant for water floods. These new types of surfactants differ from traditional surfactants used in ASP and surfactant floods by offering the following advantages: Low concentration levels – They are effective at low concentration levels normally used for ASP but do not require alkali to produce low interfacial tensions in sandstone formations. For limestone formations, sodium carbonate is normally preferred to reduce adsorption however it is not needed to produce ultra-low IFTs.Salt tolerance – They are very salt tolerant. Case studies using this new type surfactant in brines with ~110,000 PPM total dissolved solids (TDS) and ~2500 PPM divalent cations show excellent interfacial tension lowering, even at 0.05% surfactant levels. The injection water does not need to be treated or softened, which can result in a tremendous cost saving for IOR applications.Emulsion, corrosion, and scale reduction – Problems such as emulsion formation, scale, corrosion, etc. are minimized because only low concentrations of surfactant are needed and alkali is not required to produce ultra-low interfacial tensions. Examples and data using the new surfactants in both limestone and sandstone applications with various crude oils and brines are presented.