Correlation of oil-water flow behaviour in reservoir Rocks with dynamic contact angles

Document Type

Article

Publication Date

1-1-2002

Abstract

Laboratory corefloods have constituted a major step in understanding many aspects of fluids flow behaviour in reservoirs. Oil-water relative permeabilities are perhaps the most widely derived parameters from such corefloods, and they are the only recourse to account for all of the rock-fluids interactions in the mathematical models developed to describe the reservoir flow phenomena. One of the factors that has a strong influence on reservoir fluid mechanics is rock wettability. Therefore, attempts to derive wettability from corefloods are abundant in the literature spanning several decades. On the other hand, contact angles observed in crude oil-water-solid systems have been traditionally regarded as a true, or universal, measure of wettability. Hence, the obvious question becomes - is there a correlation between wettability derived from corefloods and contact angles? A definitive answer does not seem to emerge from the literature for two main reasons: (1) Craig's broad rules-of-thumb, while enabling approximate comparisons, especially between extreme cases of wettability; do not allow direct deduction of rock-fluids interactions to the extent that is required to characterize wettability, and (2) the conventional contact angle measurements have had their own share of problems in terms of reproducibility. The dual-drop-dual-crystal (DDDC) contact angle technique, reported elsewhere in the literature1, appears to resolve this long-standing reproducibility problem with contact angle measurements. This paper aims to compare wettability derived from reproducible DDDC tests in widely differing rock-fluids systems with their corresponding oil-water relative permeabilities derived from waterflood experiments using reservoir and Berea cores. In all, a total of 10 different case studies are compared, in which eight rock-fluids systems appear to yield similar wettabilities from corefloods and contact angles, while the other two differ markedly. Explanations are sought for these agreements and differences in an effort to shed more light on this important aspect of correlating core analysis with the distribution and flow mechanics of reservoir fluids.

Publication Source (Journal or Book title)

Journal of Canadian Petroleum Technology

First Page

31

Last Page

38

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