Initial Wetting in Sandstone-Development Through Time
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This thesis is a literature study of initial wettability of sandstone and how the understanding of this phenomena has developed through history. Due to the fact that wettability affect several properties to reservoir, such as fluid distribution in porous media, it will have big effect on success rate of a waterflooding. As the initial wetting have such big impact on oil recovery, it is important to get a good understanding how the wettability initially occurs in the reservoir. What affect and determines the degree of wettability to a rock. The chemical interaction between injection water and rock surface. We will research what have been the assumptions and theory regarding this earlier, and how the petroleum industry have led hydrocarbon recovery based on these assumptions, and what recent study concluded with. There is an agreement that the initial wettability is a product of a complex system in the reservoir and many parameters combined sets the final initial wettability in sandstone. For COBR (crude-oil, brine and rock), parameters such as: wetting components in crude oil, crude oil properties as a solvent, partitioning, interfacial tension, surface roughness, mineral composition etc have been in focus. Also mechanism such as electrical characterization of the oil/water interface, adsorption, adhesion, spreading and stability of water film, DLVO and electromagnetic force have been discussed. However the main mechanism behind initial wettability is still unknown, due to the fact that in-situ wettability in reservoir cannot be measured. Over long period of time, it was assumed that all sandstone reservoir are originally water-wet. Later research have indicated that this is not necessarily true. Some reservoir was found to be mixed- and even oil-wet.
Master's thesis in Petroleum engineering