A New Process for Manufacturing and Stabilizing High-Performance EOR Surfactants at Low Cost for High-Temperature, High-Salinity Oil Reservoirs

Abstract

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...

Low-Cost, High-Performance Chemicals for Enhanced Oil Recovery

“…For example, Zhao et al (2008) showed that internal olefin sulfonate (IOS) surfactants with high carbon numbers such as C 20-24 IOS and C 24-28 IOS were more effective at reducing IFT than surfactants with shorter hydrophobes. As described by Adkins et al (2010), Guerbet alkoxy sulfates (GAS) is another class of surfactants that can be made with even larger hydrophobes at lower costs. GAS surfactants show exaggerated hydrophobicity, because of its near mid-point branched alcohols with long twin tails.…”

“…As sulfonates in general are more expensive than sulfates, the costs were prohibitively high in some cases for EOR to be even considered. However, recent advancements in stabilizing sulfates at high temperatures (Adkins et al, 2010) have enabled ES to be considered for high temperature EOR applications, thus expanding the selection of surfactants immensely. Laboratory testing of these ES surfactants under optimum conditions has shown them to be effective at high temperature and they can be made at low cost.…”

Use of Co-Solvents to Improve Alkaline-Polymer Flooding

“…The surfactant formulation consisting of 0.15% TDA-13 PO SO 4 -, 0.15% C19-23 IOS with 1% IBA-5EO co-solvent showed ultra-low IFT, suitable aqueous stability and low microemulsion viscosity. Alkyl alkoxy sulfates have been shown to have a long half life even at 100°C in the presence of sodium carbonate (Adkins et al, 2010). Figure 11 details the activity map for the ASP-2.1 flood, and the salinity gradient used.…”

Design Challenges of Chemical EOR in High-Temperature, High Salinity Carbonates

“…The design of an ASP formulation for this reservoir has previously been presented (Levitt et al, 2012). However due to the high temperature and probable presence of anhydrite, it was decided that the use of sulfate surfactants, which require high pH and thus the successful propagation of alkali for stability at elevated temperatures (Adkins et al, 2010), presents an unnecessary risk in this case. A new formulation was thus optimized without alkali, using proprietary, high-salinity tolerant, anionic surfactants (patent pending).…”