Abstract
Hydraulic fracturing is an important technology for the development of unconventional resources, while the foam fracturing plays an essential role for the oil recovery in hydraulic fracturing. To further explore the anion effect of quaternary ammonium cationic surfactants on their relative performances, four fatty acid surfactants were prepared (cetyltrimethylammonium acetate (CTAAC), cetyltrimethylammonium butyrate (CTABU), cetyltrimethylammonium hexanoate (CTAHE), and cetyltrimethylammonium caprylate (CTACA)). The effect of anions on surface tension and foaming properties were discussed, and the emulsion stability was also investigated. The experimental results were presented that the CTAAC possesses the highest surface activities compared with other members in the prepared surfactants. The critical micelle concentration (CMC) and surface tension at the CMC (γCMC) increase as increasing methylene segments in the anions, the maximum surface excess concentration (Γmax), and minimum area per molecule (Amin) present an opposite trend with the increase of methylene segments. The CTAAC exhibits the best performances on foamability and foam stability than other synthesized surfactants at 70°C; the initial foam height (H0) and the foam height ratio (R3) at 0 min and 3 min are 34.9 cm and 52.9%, respectively; this is due to the lowest surface tension and shortest methylene segments. In addition, the emulsion stability was shown to follow the order of CTAAC>CTABU>CTAHE>CTACA.
Highlights
Foam fluid is a gas-liquid dispersion system
RT-IR spectral analyses indicate that the characteristic absorption peaks in this figure correspond to the functional groups in the target product, which illustrates that the synthesized surfactant is the target product
In order to research further the relationship between the anions of quaternary ammonium cationic surfactants and their relative performances, a series of quaternary ammonium cationic surfactants with novel anions are synthesized and its basic surface tension, foam properties, and emulsification power were amply investigated in this study
Summary
Foam fluid is a gas-liquid dispersion system. Because of its excellent performance, it has been widely applied in the oil and gas field development, including enhanced oil recovery, matrix acidification, gas well breakthrough control, and plugging removal [1,2,3]. By adding electrolyte, mixing the second surfactant with an opposite charge or adjusting the pH value, the shape of micelle will be changed from spherical to wormlike, and the liquid viscosity will be significantly increased due to the formation of slender wormlike micelles. Another way to improve foam stability is to use nanoparticles. Foam liquid can form a foam in the formation, which plays a good role in plugging the high permeable layer of reservoirs, thereby reducing the permeability of high permeable layers. This study is of great significance for a comprehensive understanding of the stability of foam in porous media and for improving foam flooding theory
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