Development of Thermally and Chemically Stable Large-Hydrophobe Alkoxy Carboxylate Surfactants
Abstract
Abstract The Guerbet reaction produces large, branched hydrophobes through the dimerization of linear alcohols. High-performance, low-cost enhanced oil recovery (EOR) surfactants are produced by carboxylation (carboxymethylation) of large Guerbet alkoxylates. Alkoxy groups such as propylene oxide (PO) and ethylene oxide (EO) are incorporated as extenders to the Guerbet alcohol, followed by carboxylation to make the anionic surfactant. Previously, the use of low-cost Guerbet alkoxy sulfate surfactants for EOR applications at high temperatures was established by enhancing their thermal stability when the pH is maintained at 10–11. Alternative thermally and chemically stable anionic surfactant structures are highly desired, especially for application under conditions where alkali usage is prohibitive. These novel large-hydrophobe carboxylate surfactants meet this need. In addition, the Guerbet alkoxy carboxylate structure can be tailored to fit the specific EOR requirements. These surfactants are stable at elevated temperatures both with and without alkali, and furthermore they can be used in environments of high salinity and high hardness (high concentration of divalent ions). Carboxylate surfactants have been used in formulations to produce ultra-low interfacial tensions with low microemulsion viscosities for a wide variety of crude oils under a large range of reservoir conditions. A parallel paper titled "Novel Large-Hydrophobe Alkoxy Carboxylate Surfactants for Enhanced Oil Recovery" will discuss the application of these surfactants. Thus, the advent of this class of cost-effective surfactants greatly broadens the application of chemical EOR.