Abstract
Switchable ethoxylated amine surfactants are readily soluble in CO2 and high-saline brines. The objective of the current work is to maximize the foamability and stability of CO2 foam at 150 °F (65 °C) through adjustments in the surfactant concentration, pH, and brine salinity. From the results, the authors recommend potential applications of Ethomeen C12 (EC12) for CO2 foam in the oil/gas industry. Foam stability tests helped determine the optimum parameters for CO2 foam stability at 77 °F (25 °C) and 150 °F (65 °C). The surface tension of EC12 as a function of concentration was evaluated using a drop-shape analyzer. Maximum foam stability was observed for a solution comprising of 1.5 wt% EC12, 25 wt% NaCl, and pH 6.5 at 150 °F (65 °C). The interactions with the salts allowed closer packing of the surfactant molecules at the lamellae and strengthening the foam. At a pH of 2.5, the absence of salt led to poor foam stability. However, at the same pH and in the presence of sodium chloride, the foam was stable for longer periods of time due to the salt influence. The surface tension gradients had a direct relationship to foam stability. There was a strong resistance to foam degradation when multivalent ions were present with the surfactant.