(126b) Chemically Enhanced Oil Recovery: Novel Surfactants - the Concept of Large Hydrophobe Alkoxy Carboxylate Surfactants

The large hydrophobe concept in surfactants for Chemical Enhanced Oil Recovery (CEOR) is a very recent phenomenon. An elegant method of making a large hydrophobe which can be converted into an effective surfactant molecule is the well known Guerbet reaction. This reaction produces large, branched hydrophobes through the dimerization of linear alcohols. High-performance, cost-effective 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) can be easily added as extenders to the Guerbet alcohol, followed by carboxylation to make the anionic surfactant. Previously, the use of cost-effective Guerbet alkoxy sulfate surfactants for EOR applications at high temperatures was established by greatly enhancing their thermal stability at high pH (10-11). Alternative thermally and chemically stable anionic surfactant molecules 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 structures can be tailored to fit the specific EOR requirements. These surfactants are stable at elevated temperatures both with and without alkali, and furthermore, they may be used in environments of high salinity and high hardness (high concentration of divalent ions). These 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 broad range of reservoir conditions. Both sandstone and carbonate corefloods have been conducted with excellent results. Thus, the new carboxylate surfactants provide a breakthrough that greatly enhances the commercial potential of CEOR.