Switchable Diamine Surfactants for CO2 Mobility Control in Enhanced Oil Recovery and Sequestration

Abstract

The design of switchable amine surfactants for CO2 EOR in carbonate reservoirs at high temperatures is challenging because of the increase in the pH due to dissolution of calcium carbonate at acidic conditions. The increased pH hinders the protonation of the surfactant and its aqueous solubility. In this work, the addition of a second amine headgroup ensured that C16-18 N(EO) C3N(EO)2 is soluble in 22%TDS brine at neutral pH conditions. Also, captive bubble tensiometry measurements confirmed the activity of the surfactant at the C-W interface by large reduction in the interfacial tension coupled with high adsorption. Also, the surfactant generated viscous foam that can stabilize the displacement front in CO2 EOR processes and decrease the mobility of CO2 for enhanced CO2 sequestration.

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

“…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). Reactions between primary, secondary or tertiary amines with an appropriate alkoxylation agent generated these ethoxylated amines.…”

Two-Step Adsorption of a Switchable Tertiary Amine Surfactant Measured Using a Quartz Crystal Microbalance with Dissipation

“…At pH = 7, the degree of protonation at 0.1 M NaCl can be 3 times higher than that under 0.001 M NaCl. At higher ionic strengths, the electrostatic repulsion between the protons in solution and protonated amines on the DTTM is screened, which results in higher protonation . Furthermore, with increased protonation, there is increased hydration of the surfactant and thus the hydrophilicity of DTTM increases as the pH decreases or the ionic strength increases …”

“…In order to calculate the protonation degree of DTTM, titration experiments are conducted. , Solutions of DTTM at different ionic strengths were prepared and titrated using HCl at room temperature. The protonation degree is determined based on system charge balance showed below where θ is protonation degree of DTTM, C Cl – is the concentration of Cl – , C OH – is the concentration of OH – , C H + is the concentration of H + , V titrand is the volume of titrant used, C DTTM is the initial concentration of DTTM, and V DTTM is the initial volume of DTTM solution.…”

“…In order to calculate the protonation degree of DTTM, titration experiments are conducted. 6,10 Solutions of DTTM at different ionic strengths were prepared and titrated using HCl at room temperature. The protonation degree is determined based on system charge balance showed below…”

“…Switchable surfactants are an exciting class of molecules whose amphiphilicity can be tuned in response to external stimuli such as temperature, pH, , and light. , These stimuli-responsive surfactants have been utilized in a variety of processes, with applications ranging from foams for oil recovery , and phase inversion emulsions for food production, drug delivery, and detergency. , More recently, switchable surfactants have shown enhanced chemical and thermal stability for applications requiring high temperatures or salinities. − Adsorption of these switchable surfactants to solid substrates can be used to alter the surface properties of substrates, such as wettability, hydrophobicity, or surface charge . Despite the numerous important applications of stimuli-responsive surfactants, few studies have reported the adsorption mechanisms of the switchable surfactants with solid substrates.…”