Non-monotonicity of the Contact Angle from NaCl and MgCl₂ Concentrations in Two Petroleum Fluids on Atomistically Smooth Surfaces

Abstract

Wetting and alteration of wetting are among the most important material properties of fluid−fluid−substrate systems in biological and industrial systems. An important industrial application of wetting and wetting alteration is related to displacement of crude oil by water injection in porous media. Water injection in oil reservoirs has been used since the early periods of oil production. Recently, it has been discovered that the salt concentration in the injected water may have a significant effect on the oil recovery. The process is under active research for the need of an improved understanding. In this work, we investigate the governing elements of surface wettability with two different crude oils on two atomistically smooth surfaces (mica and quartz) and one smooth surface (calcite) as a function of the salt concentration (0−3 M) and type (mono-versus divalent). We investigate the change of wettability from NaCl and MgCl 2 salts over a wide concentration for the first time. The measurements are based on long enough aging times and droplet sizes that give equilibrium and size-independent contact angles. Our measurements show a non-monotonic behavior, in that, as NaCl concentration increases, there is a decrease (increase of water-wetting) and then an increase (decrease of water-wetting) of the contact angle in all of the systems that we have studied. MgCl 2 salt shows two trends with an increasing concentration. For mica and quartz, there is first a decrease of the contact angle and then an increase followed by a second sharp decrease at high MgCl 2 concentrations. For calcite substrate, we observe an increase of the contact angle reaching a maximum and then a decrease with an increasing salt concentration. These observations have profound implications on the effect of salts on wettability alteration. The measurements have set the stage for atomistic simulations for a molecular understanding of the salt effect in complex fluids.

Effects of pore fluids on quasi‐static shear modulus caused by pore‐scale interfacial phenomena

“…There is a decrease of the contact angle as the NaCl concentration increases and then an increase of the contact angle with a further increase in NaCl concentration. The trend is the same on quartz, mica, and calcite surfaces (Aslan et al 2016). This implies that different salts and salt concentrations alter the capillary properties of pore liquids including surface tension and contact angles.…”

“…The trend is the same on quartz, mica, and calcite surfaces (Aslan et al . ). This implies that different salts and salt concentrations alter the capillary properties of pore liquids including surface tension and contact angles.…”

“…For example, the addition of inorganic salts to water raises the surface tension approximately linearly with the salt concentration above 0.01 mole/l, whereas at dilute salt concentrations the interfacial tension decreases with salt concentration due to Jones-Ray effect (Petersen and Saykally 2006). Aslan, Fathi Najafabadi and Firoozabadi (2016) show a non-monotonic dependence of the contact angle on smooth surfaces of different rocks as a function of salt concentration. There is a decrease of the contact angle as the NaCl concentration increases and then an increase of the contact angle with a further increase in NaCl concentration.…”

Deposition of Inorganic Carbonate, Sulfate, and Sulfide Scales on Antifouling Surfaces in Multiphase Flow

“…in distilled water and 130° in 1M NaCl 46 . High hydrophilicity and low oleophilicity of calcite particles therefore leads to complete dispersion within the aqueous phase, with a negligible amount of crystals stabilized at the oil/water interface.…”

Interactions between apolar, basic and acidic model oils and a calcite surface

“…(4) Low-salinity water-flooding with salinity lower than 5000 ppm has been found to be able to improve oil recovery (5) due to wettability alteration of reservoir surfaces. (6)(7)(8) The mechanisms of low-salinity water-flooding leading to wettability alteration are not yet fully understood, but various parameters, such as specific ion adsorption, (9)(10)(11) pH, electrostatic double layer expansion, multi-ion exchange, (12) and chemical mechanisms, (3,(13)(14) are important.…”