An alcohol dimerization process known as the Guerbet reaction is used to create large alcohol structures for the production of the corresponding alkoxy sulfate surfactants. In the alcohol industry, Guerbet (dimer) alcohols are considered the "gold" standard for large, branched alcohols. These Guerbet alcohols tend to be more expensive than other alcohols when produced in high purity for various industrial applications. The high cost is mainly due to driving the reaction to completion and/or stripping-off of the unreacted monomer alcohol to produce high purity. However, inexpensive Guerbet alcohols (GA) can be prepared by aiming for less than quantitative conversion during the alcohol dimerization process. The resultant blend of 85-95% GA and 5-15% monomer alcohol is subsequently used in the alkoxylation process to add propylene oxide and/or ethylene oxide, followed by sulfation. Through the use of this new Guerbet process, these surfactants can be manufactured at low cost when made as sulfates as opposed to sulfonates. For example, a C32 GA can be produced from a C16 alcohol. These and other sulfate surfactants can be stabilized at high temperature with alkali. This is a surprising discovery that greatly increases the availability of low-cost, high performance surfactants for high temperature reservoirs. Guerbet Alkoxy Sulfate SurfactantsWhen the equivalent alkane carbon number (EACN) of a crude oil is higher than about 12 surfactants with very large hydrophobes and branched structures are required to obtain ultra-low interfacial tensions and low microemulsion viscosities (Liu et al., 2007) and this is even more difficult to achieve at high temperature and/or high salinity and hardness. However, the cost of these very large hydrophobe surfactants can be prohibitive. However, inexpensive Guerbet alcohols (GA) can be prepared by aiming for less than quantitative conversion during the alcohol dimerization process.The Guerbet reaction dimerizes a linear alcohol using base catalysis at high temperatures (for example 230 °C) to produce near mid-point branching. (O'Lenick Jr., 2001) The Guerbet alcohols (GA) are considered the "gold" standard for large, branched alcohols which are low melting point liquids. Very large hydrophobe structures can be produced from smaller linear alcohols using the Guerbet reaction. For example, a C32 GA can be produced from a C16 alcohol. These Guerbet alcohols (GA) can then be used in the production of corresponding alkoxy sulfate surfactants. Guerbet alkoxy sulfate surfactants have previously been studied at the air-water (Varadaraj et al., 1991) and oil-water interfaces (Aoudia et al., 1995). These anionic surfactants can be produced by adding propylene oxide (PO) and ethylene oxide (EO) units to the GA, followed by sulfation (O'Lenick Jr. and Parkinson, 1996). By varying the amount of PO and EO in the Guerbet surfactants, they can be tailored to fit specific EOR needs.Guerbet alcohols tend to be more expensive than other alcohols when produced in high purity for various industrial appli...
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.
We have found that the addition of low concentrations of certain inexpensive light cosolvents to alkaline/polymer (AP) solutions dramatically improves the performance of AP corefloods in two important ways. First, the addition of cosolvent promotes the formation of low-viscosity microemulsions rather than viscous macroemulsions. Second, these light cosolvents greatly improve the phase behavior in a way that can be tailored to a particular oil, temperature, and salinity. This new chemical enhanced-oil-recovery (EOR) technology uses polymer for mobility control and has been termed alkali/cosolvent/polymer (ACP) flooding. ACP corefloods perform as well as alkaline/surfactant/polymer (ASP) corefloods while being simpler and more robust. We report 12 successful ACP corefloods using four different crude oils ranging from 12 to 24 API. The ACP process shows special promise for heavy oils, which tend to have large fractions of soap-forming acidic components, but is applicable across a wide range of oil gravity.
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