Ethoxylated Cationic Surfactants for CO2 EOR in High Temperature, High Salinity Reservoirs

Abstract

Despite significant interest in CO 2 foams for EOR, very few studies have reported stable foams at high temperatures and high salinities, which are often encountered in the Middle East and elsewhere. Stable CO 2 /water (C/W) foams at high temperatures up to 120 o C and salinities have been achieved with ethoxylated cationic surfactants. The surfactants were shown to stabilize C/W foams with high salinity brine with NaCl concentration up to 182 g/L at 120 °C, 3400 psia, and to form unstable dodecane/water emulsions with the 120 g/L NaCl brine solutions. Thus, the foams have the potential to provide mobility control to prevent loses of CO 2 in high permeability regions, but simultaneously allow high permeability in the presence of residual oil. The surfactants are soluble in CO 2 and thus may be injected in the CO 2 phase to simplify the EOR process. The aqueous solubility of the surfactant at high temperatures is enhanced with the appropriate number of EO groups on the amine head group. Viscosities of high-pressure C/W foams (emulsions) formed with these surfactants were investigated by capillary rheology. These hybrid cationic/nonionic surfactants combine the high cloud points of ionic surfactants with high solubilities in CO 2 of nonionic surfactants. Furthermore, the variation of the tail length and the degree of ethoxylation offer great flexibility for stabilizing CO 2 foams for EOR at high temperatures and high salinities. Ethoxylated cocoamine exhibited lower adsorption on calcite than that on dolomite, given the presence of silica sites in the latter. High divalent ion concentrations in 22% total dissolved solids (TDS) brine contributed to the reduction of surfactant adsorption on silica sites in the dolomite powder.

Review of surfactant-assisted chemical enhanced oil recovery for carbonate reservoirs: challenges and future perspectives

“…To overcome these limitations, ethoxylated nonionic to cationic switchable amine surfactants were designed and introduced in a series of sand pack experiments (Chen et al 2012(Chen et al , 2014. Ethoxylated amines are switchable from being nonionic in brine to cationic in the presence of an acidic aqueous phase such as CO 2 (Elhag et al 2014a).…”

Supercritical CO2-Foam - The Importance of CO2 Density on Foams Performance

“…However, many papers report similar low mobility reductions to supercritical CO 2 as we achieved. (Adkins et al, 2009Chabert et al, 2012;Chen et al, 2012;Enick and Olsen, 2012;McLendon et al, 2012;Sanders et al, 2010;Xing et al, 2012). Interestingly, core foam tests in Berea sandstone without oil generated very strong supercritical CO 2 -foam using high surfactant concentrations of a Betaine instead of an AOS (Bian et al, 2012).…”

“…CO 2 -foams are described as weaker. The numerous differences between CO 2 and N 2 are frequently discussed in context to the greater mobility of CO 2 -foams attained: surfactant properties against different interfaces, solubility effects related to CO 2 , lower interfacial tension between supercritical CO 2 and lamella, lower pH with CO 2 -foam, wettability alteration effects with the CO 2 -brine-rock system, greater density and viscosity properties to supercritical CO 2 (Adkins et al, 2009Chaubert et al, 2012;Chou, 1991;Farajzadeh et al, 2009Farajzadeh et al, , 2011Gauglitz et al, 2002;Heller 1994;Kibodeaux, 1997;Nonnekes et al, 2012;Rossen, 1996;Kuhlman et al, 1992).…”

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

“…Chen et al (2012) and Elhag et al (2014) demonstrated that apparent viscosities of foams measured with a capillary viscometer were more than 8 cP at variable temperatures and foam qualities with a switchable ethoxylated cationic CO 2 -philic surfactant. They found that the delivery media of CO 2 -soluble surfactant imposed less impact.…”

“…Adkins et al (2010a, b) and Chen et al (2010) have proven that a branched hydrocarbon nonionic surfactant can effectively reduce the contact of CO 2 and water phases and raise the surface pressure and the surfactant efficiency (the concentration to produce 20 mN/m interfacial tension reductions). Chen et al (2012) developed a switchable ethoxylated cationic CO 2 -philic surfactant which was able to stabilize CO 2 /water foams up to 182 g/L at 120°C, 3400 psia. Those hybrid surfactants combined the high cloud points of ionic surfactants with high solubility in CO 2 of nonionic surfactants.…”