Development of Thermally and Chemically Stable Large-Hydrophobe Alkoxy Carboxylate Surfactants

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.

New Correlation to Predict the Optimum Surfactant Structure for EOR

“…The development and the application of GAS surfactants to chemical EOR are discussed in Adkins et al (2010) and Yang et al (2010). Sulfates require high pH at elevated temperatures (> 65 C) for thermal stability whereas the carboxylates are stable up to at least 120 C. The development and application of GAC surfactants to chemical EOR are discussed in Adkins et al (2012) and Lu et al (2012).…”

Mixtures of Anionic/Cationic Surfactants: A New Approach for Enhanced Oil Recovery in Low-Salinity, High-Temperature Sandstone Reservoir

“…These lower salinities are challenging because it is difficult to find surfactants for producing ultralow crude-oil/water IFT at such reservoir conditions. Recently, it has been possible to obtain suitable surfactants for harsh reservoir conditions of elevated temperature and hardness with large/bulky hydrophobes, such as polymeric surfactants (Wang et al 2010;Zhang and Tang 2010;Elraies et al 2011;Elraies and Tan 2012), dimeric (gemini) and oligomeric surfactants (Bae and Chou 1989;Zana 2002;Iglauer et al 2010;Gao and Sharma 2012;Wei 2012), Guerbet alkoxy sulfates and Guerbet alkoxy carboxylates (Adkins et al 2012;Lu et al 2012), and alkoxy carboxylates and/or sulfonates (Berger and Berger 2007;Berger et al 2009;Weerasooriya and Pope 2012) made from alkoxylating with propylene oxide and ethylene oxide groups. By tuning propylene oxide and ethylene oxide numbers or the use of multiple hydrophilic groups in surfactant molecule, it is possible to obtain the suitable hydrophilic-lipophilic balance needed to achieve ultralow IFT as well as other performance characteristics needed for efficient oil recovery.…”

Optimization of Gravity-Stable Surfactant Flooding

“…Surfactants can reduce the water/oil IFT to an ultra-low level (on the order of 10 dynes/cm or lower) to provide high capillary numbers needed to overcome the capillary forces and mobilize residual oil under a wide range of reservoir conditions (Yang et al, 2010;Adkins et al, 2010;Barnes et al, 2012;Bataweel and Nasr-El-Din, 2012;Puerto et al, 2012;Adkins et al, 2012;Tabary et al, 2013;Lu et al, 2014aLu et al, , 2014bLu et al, , 2014cLu, 2014;Liyanage et al, 2015).…”