The Role of Wettability in Petroleum Recovery

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Various findings on core handling effects and crude oil/brine/rock (COBR) interactions have indicated how the wettability of a core sample is altered when retrieved from a reservoir. Moreover, it is revealed that wettability of a core will affect almost all types of physical parameters necessary for reservoir management, such as capillary pressure. However, the most accurate results are obtained when native or restored-state cores are used with native crude oil and brine at reservoir temperature and pressure. Such conditions provide core that have the same wettability as the reservoir. Equally, the wettability of originally water-wet rock can be altered by the adsorption of polar compounds and/or the deposition of organic material that was originally in the crude oil. The degree of alteration is determined by the interaction of the oil constituents, the mineral surface, and the brine chemistry. Factors that influence wettability alteration are considered, and how this in turn affects the capillary pressure, is determined. Due to the capillary pressure dependence on water saturation, the effect of wettability alteration on reserve estimation through the initial water saturation is shown. The implications for oil recovery prediction and reservoir management are discussed. The main objective is to do a critical analysis on how wettability alteration dictates the success or failure of reservoir management irrespective of the technical or operational input, early in the life of a reservoir. It is believed that reserve estimation at the early stage is either optimistic or pessimistic with the consequent effect on oil recovery prediction and reservoir planning. The overall effect would be poor reservoir management at the early life of the reservoir, which effects on the later life of the reservoir is inestimable. This explains why the petroleum business is the riskiest business in the world. This would continue to be so unless a method is devised to measure reservoir parameters in situ, devoid of wettability alteration to any extent.