Relationship Between Crude Oil Composition and Physical-Chemical Properties
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- Department of Chemistry 
Improving oil recovery by low salinity waterflooding has been of interest in both laboratories and fields in recent years. Understanding how the underlying mechanism affects the final recovery is necessary in order to optimize waterflooding and chemical injection. A physical-chemical investigation of the crude oil/brine/reservoir rock system, and correlation with crude oil composition, is the focus of this thesis. Three crude oils from different fields in the North Sea have been investigated. Interactions between the crude oils and brine were investigated by studies of interfacial tension and zeta potentials. Contact angles were studied to examine the wettability behaviour in the crude oil/brine/rock system. The interactions were studied as a function of brine pH and ionic strength. A decrease in interfacial tension and zeta potential with increasing pH and ionic strength, was observed for all crude oils. A presence of small amounts of divalent calcium cations were found to increase the interfacial tension at pH 11, but decrease the interfacial tension at pH 9. It proved difficult to identify any trends in the contact angle measurements, however one of the crude oils appeared to have higher contact angles than the others. The crude oil with lowest acidity, was found to have the highest interfacial activity. The lowest interfacial activity was observed for the crude oil with the highest asphaltene content.