Venezuelan Annual Meeting, 6–9 November, Caracas, Venezuela

One of the first steps in treating physical quantities or entities in technical discussions is to define them. The technologist prides himself on his insistence to precisely state what he means, when he employs certain terms. If one takes, however, the trouble to search the literature for a clear-cut definition of wettability one is apt to search in vain. The truth Of the matter is that some or the leading authorities in the field flatly declare that a definition Of absolute wettability is impossible to state. They resort to a term called "relative wettability" which connotes the preference of a given liquid to spread over a solid surface in the presence of a second liquid. Others state that wettability is a manifestation of the interaction between liquids and solid surfaces, which is a broad and general statement indeed. Still others define wettability strictly in terms or contact angles for the solid-water system. Considering the indefinite character of the wettability term one expects some difficulties in measuring some of its effects on various core parameters. Nevertheless, even at the risk or embarking on what may appear to be a naive approach, attempts to study the effects or wettability on various core parameters are apt to result in some worthwhile contributions to our understanding of rock properties. Perhaps one of the most important facts to realize in the beginning is that most investigations show that there is really no such thing as an oil-wet or water-wet reservoir rock.

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