Chemical Enhanced Oil Recovery: Novel Surfactants - The Concept of Large-Hydrophobe Alkoxy Carboxylate Surfactants

摘要

The large hydrophobe concept in surfactants for Chemical Enhanced OilrnRecovery (CEOR) is a very recent phenomenon. An elegant method of making a largernhydrophobe which can be converted into an effective surfactant molecule is the wellrnknown Guerbet reaction. This reaction produces large, branched hydrophobes through therndimerization of linear alcohols. High-performance, cost-effective Enhanced Oil Recoveryrn(EOR) surfactants are produced by carboxylation (carboxymethylation) of large Guerbetrnalkoxylates. Alkoxy groups such as propylene oxide (PO) and ethylene oxide (EO) can berneasily added as extenders to the Guerbet alcohol, followed by carboxylation to make thernanionic surfactant. Previously, the use of cost-effective Guerbet alkoxy sulfate surfactantsrnfor EOR applications at high temperatures was established by greatly enhancing theirrnthermal stability at high pH (10-11). Alternative thermally and chemically stable anionicrnsurfactant molecules are highly desired, especially for application under conditions wherernalkali usage is prohibitive. These novel large-hydrophobe carboxylate surfactants meetrnthis need. In addition, the Guerbet alkoxy carboxylate structures can be tailored to fit thernspecific EOR requirements. These surfactants are stable at elevated temperatures bothrnwith and without alkali, and furthermore, they may be used in environments of highrnsalinity and high hardness (high concentration of divalent ions). These carboxylaternsurfactants have been used in formulations to produce ultra-low interfacial tensions withrnlow microemulsion viscosities for a wide variety of crude oils under a broad range ofrnreservoir conditions. Both sandstone and carbonate corefloods have been conducted withrnexcellent results. Thus, the new carboxylate surfactants provide a breakthrough thatrngreatly enhances the commercial potential of CEOR.