Static adsorption of a switchable diamine surfactant on natural and synthetic minerals for high-salinity carbonate reservoirs

Abstract

The static adsorption of Duomeen TTM (DTTM, C16-18N(CH3)C3N(CH3)2), a switchable surfactant, is investigated as a function of mineral type, pH, salinity, temperature, and concentration. At approximately neutral pH, DTTM is protonated, becoming positively charged, and exhibits low adsorption on pure calcite. However, relatively high adsorption of DTTM is observed on natural carbonate, silica, and kaolin due to the presence of negatively charged siliceous minerals, indicating that the mineral type is a predominant factor in DTTM adsorption. Lower DTTM adsorption is detected due to increased NaCl salinity or the presence of multivalent ions (Mg2+, Ca2+, Cr3+). We also discuss how adjusting the solution pH affects a novel competitive adsorption mechanism between the DTTM protonation degree and surface charge change. Increases in temperature lead to a decrease in DTTM adsorption on silica and dolomite. Interestingly, DTTM tends to have higher adsorption at elevated temperatures. Additionally, DTTM can associate into higher-order assemblies at high concentrations, which in turn increases its adsorption due to the crosslinked structure.