Understanding the behaviour of heterogeneous systems has been of particular significance to crude oil production. Adsorption of crude oil surface-active species to reservoir rocks and aqueous interfaces has consequences for oil recovery and its separation from water. Therefore, an evaluation of heterogeneous systems involved in crude oil recovery has been the main focus of this thesis. After a general introduction, the thesis is divided into five sections: crude oil chemistry, solid wettability, asphaltene adsorption, emulsion stability and characterisation of interfacial films. The first section considers the chemistry of crude oil through its separation into fractions, based on polarity and solubility differences. The second is the characterisation of oil-brine-rock interactions and wettability alteration of bitumen-coated sand surfaces by nuclear magnetic resonance (NMR) relaxometry, and its relevance in low salinity waterflooding. In the third section, a quantification of asphaltene adsorption on sand is performed in the presence of pre-adsorbed water. The fourth section contains an evaluation of the potential of magnetic resonance imaging (MRI) in the visualisation of crude oil emulsions, with particular emphasis on oil-water separation. The final section is aimed at identifying surface-active species responsible for influencing solid-liquid and liquid-liquid interactions.