Carbonate rock reservoirs comprise approximately 60% of the world’s oil and gas reserves. Complex flow mechanisms and strong adsorption of crude oil on carbonate formation surfaces can reduce hydrocarbon recovery of an oil-wet carbonate reservoir to as low as 10%. Low salinity waterflooding (LSW) has been confirmed as a promising technique to improve the oil recovery factor. However, the principal mechanism underpinning this recovery method is not fully understood, which poses a challenge toward designing the optimal salinity and ionic composition of any injection solution. In general, it is believed that there is more than one mechanism involved in LSW of carbonates; even though wettability alteration toward a more desirable state for oil to be recovered could be the main cause during LSW, how this alteration happens is still the subject of debate. This paper reviews different working conditions of LSW, previous studies, and field observations, alongside the proposed interfacial mechanisms which affect the colloidal interactions at oil–rock–brine interfaces. This paper provides a comprehensive review of studies on LSW in carbonate formation and further analyzes the latest achievements of LSW application in carbonates, which helps to better understand the challenges involved in these complicated multicomponent systems and potentially benefits the oil production industry.

Lubricant additives, based on inorganic nanoparticles coated with organic outer layer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating the great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with excellent levels of performance. The organic part in the hybrid materials improves their flexibility and stability, while the inorganic part is responsible for hardness. The relationship between the design parameters of the organic coatings, such as molecular architecture and the lubrication performance, however, remains to be fully elucidated. A survey of current understanding of hybrid nanoparticles as lubricant additives is presented in this review.

The influence of different types of salts (NaCl, CaCl ${}_2$ , MgCl ${}_2$ , NaHCO ${}_3$ , and Na ${}_2$ SO ${}_4$ ) on the surface characteristics of unconditioned calcite and dolomite particles, and conditioned with stearic acid, was investigated. This study used zeta potential measurements to gain fundamental understanding of physico-chemical mechanisms involved in surface charge modification of carbonate minerals in the presence of diluted salt solutions. By increasing the salt concentration of divalent cationic salt solution (CaCl ${}_2$ and MgCl ${}_2$ ), the zeta potential of calcite particles was altered, resulting in charge reversal from negative to positive, while dolomite particles maintained positive zeta potential. This is due to the adsorption of potential-determining cations (Ca ${}^{2+}$ and Mg ${}^{2+}$ ), and consequent changes in the structure of the diffuse layer, predominantly driven by coulombic interactions. On the other hand, chemical adsorption of potential-determining anions (HCO ${}_3^{-}$ and SO ${}_4^{2-}$ ) maintained the negative zeta potential of carbonate surfaces and increased its magnitude up to 10 mM, before decreasing at higher salt concentrations. Physisorption of stearic acid molecules on the calcite and dolomite surfaces changed the zeta potential to more negative values in all solutions. It is argued that divalent cations (Ca ${}^{2+}$ and Mg ${}^{2+}$ ) would result in positive and neutral complexes with stearic acid molecules, which may result in strongly bound stearic acid films, whereas ions resulting in negative mineral surface charges (SO ${}_4^{2-}$ and HCO ${}_3^{-}$ ) will cause stearic acid films to be loosely bound to the carbonate mineral surfaces. The suggested mechanism for surface charge modification of carbonates, in the presence of different ions, is changes in both distribution of ions in the diffuse layer and its structure as a result of ion adsorption to the crystal lattice by having a positive contribution to the disjoining pressures when changing electrolyte concentration. This work extends the current knowledge base for dynamic water injection design by determining the effect of salt concentration on surface electrostatics.

A quantitative investigation of the responses of surface-grown biocompatible brushes of poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) to different types of salt has been carried out using ellipsometry, quartz crystal microbalance (QCM) measurements, and friction force microscopy (FFM). Both cations and anions of varying valency over a wide range of concentrations were examined. Ellipsometry shows that the height of the brushes is largely independent of the ionic strength, confirming that the degree of swelling of the polymer is independent of the ionic character of the medium. In contrast, QCM measurements reveal significant changes in mass and dissipation to the PMPC brush layer, suggesting that ions bind to phosphorylcholine (PC) groups in PMPC molecules, which results in changes in the stiffness of the brush layer, and the binding affinity varies with salt type. Nanotribological measurements made using friction force microscopy show that the coefficient of friction decreases with increasing ionic strength for a variety of salts, supporting the conclusion drawn from QCM measurements. It is proposed that the binding of ions to the PMPC molecules does not change their hydration state, and hence the height of the surface-grown polymeric brushes. However, the balance of the intra- and intermolecular interactions is strongly dependent upon the ionic character of the medium between the hydrated chains, modulating the interactions between the zwitterionic PC pendant groups and, consequently, the stiffness of the PMPC molecules in the brush layer.

The attachment of microbial cells to solid substrata is a primary ecological strategy for the survival of species and the development of specific activity and function within communities. An hypothesis arising from a biological sciences perspective may be stated as follows: The attachment of microbes to interfaces is controlled by the macromolecular structure of the cell wall and the functional genes that are induced for its biological synthesis. Following logically from this is the view that diverse attached cell behaviour is mediated by the physical and chemical interactions of these macromolecules in the interfacial region and with other cells. This aspect can be reduced to its simplest form by treating physico-chemical interactions as colloidal forces acting between an isolated cell and a solid or pseudo solid substratum. These forces can be analysed by established methods rooted in DLVO (Derjaguin, Landau, Verwey and Overbeek) theory. Such a methodology provides little insight into what governs changes in the behaviour of the cell wall attached to surfaces, or indeed other cells. Nor does it shed any light on the expulsion of macromolecules that modify the interface such as formation of slime layers. These physical and chemical problems must be treated at the more fundamental level of the structure and behaviour of the individual components of the cell wall, for example biosurfactants and extracellular polysaccharides. This allows us to restate the above hypothesis in physical sciences terms: Cell attachment and related cell growth behaviour is mediated by macromolecular physics and chemistry in the interfacial environment. Ecological success depends on the genetic potential to favourably influence the interface through adaptation of the macromolecular structure. We present research that merges these two perspectives. This is achieved by quantifying attached cell growth for genetically diverse model organisms, building chemical models that capture the variations in interfacial structure and quantifying the resulting physical interactions. Experimental observations combine aqueous chemistry techniques with surface spectroscopy in order to elucidate the cell wall structure. Atomic force microscopy methods quantify the physical interactions between the solid substrata and key components of the cell wall such as macromolecular biosurfactants. Our current approach focuses on considering individually mycolic acids or longer chain polymers harvested from cells, as well as characterised whole cells. This approach allows us to use a multifactorial approach to address the relative impact of the individual components of the cell wall in contact with model surfaces. We then combine these components to increase complexity step-wise, while comparing with the behaviour of entire cells. Eventually, such an approach should allow us to estimate and understand the primary factors governing microbial cell adhesion. Although the work addresses the cell–mineral interface at a fundamental level, the research is driven by a range of technology needs. The initial rationale was improved prediction of contaminant degradation in natural environments (soils, sediments, aquifers) for environmental cleanup. However, this area of research addresses a wide range of biotechnology areas including improved understanding of pathogen survival (e.g., in surgical environments), better process intensification in biomanufacturing (biofilm technologies) and new product development.