The purpose of this study was to characterize model, outcrop, and reservoir samples under low salinity, different cationic valency, and pH ranges. Potentiometric titrations and zeta potential measurements were performed in order to determine the surface properties at different pH. The extent of ion adsorption on the mineral surfaces was found by the difference between the two approaches. X-ray diffraction and cation exchange capacity measurements were also performed. All samples except calcite showed high, negative zeta potentials in fresh water at pH > 6, followed by NaCl, low salinity solution (LSS), and solutions with divalent cations. The effect of ion valency on the zeta potential at low pH values was not prominent. Above pH 8, H⁺ and OH⁻ were not potential determining ions for samples that contained calcite and dolomite more than 1.5%. Above pH 8, the presence of carbonates in outcrop and reservoir samples significantly affected the zeta potential by reversing the charge in divalent solutions. The cation exchange capacity of predominant quartz, mixed quartz-clay-carbonate, and quartz-carbonate sandstones was 0.0, 0.2, and 2.2 meqv/100 g, respectively. The compositional differences between the samples were also reflected in the point of zero charge (pzc) values. Samples containing more than 1.5% carbonates had pzc in the range of pH 8–9, while samples with small fractions of carbonates or without carbonates had pzc values in the range of pH 2.9–3.3.

Nanotechnology is widely recognized for having important applications in many industries, one of which is oil and gas. Both environmental and cost benefits can be achieved when using nanoparticles for the separation of water and oil or further purification of produced water. More efficient emulsion separation can be achieved by selective adsorption of naturally present stabilizing components or magnetic action applied to nanoparticle-tagged droplets. The focus of this review is given to both nanoparticles and nanocomposites that have been studied with respect to asphaltene adsorption, crude oil demulsification, and produced water treatment, as well as oil spill cleanup and improvement of antifouling resistance of filtration membranes. Asphaltene chemistry and its role in emulsion stabilization are discussed in detail.

Asphaltenes are regarded as troublesome components of crude oils as their precipitation and deposition inside production wells and downstream infrastructure often result in a reduction of production capacity and, in critical cases, production shut-in. It has been shown that asphaltene deposition on conductive surfaces can be controlled by the application of an electric field. The electric field has been used to either inhibit or accelerate asphaltene deposition. This paper reviews asphaltene behavior in an electric field. It describes the structure and electric properties of asphaltenes as well as their electrokinetic behavior. State-of-the-art asphaltene electrodeposition and separation from both model and crude oils using electric fields are also discussed. The influence of parameters such as asphaltene chemistry, crude oil composition, pH, electric field strength, and flow conditions on the asphaltene electrodeposition process is addressed, and the effect of asphaltene interactions with themselves and other crude oil components is evaluated. A comprehensive literature survey reported the electrodeposition on both positive and negative electrodes, which suggests the complexity of the process. It has been shown that asphaltene charges can be tailored by changing the process parameters. Because of the high energy efficiency and relatively simple process, asphaltene electrodeposition is currently a key solution for removal of asphaltenes from crude oils. This review also highlights the main challenges and knowledge gaps associated with the asphaltene electrodeposition process.