Rock/Crude-Oil Interactions and Wettability: An Attempt to Understand Their Interrelation

Abstract

ABSTRACT To emphasize the occurrence of non-water-wet reservoirs, a literature review of this topic is made followed by a description of our findings concerning the evaluation of the wettability of some 20 reservoirs from Europe, North Africa and the Middle East. Then this paper describes various experimental contributions to the understanding of rock/crude-oil interactions which are responsible for the occurrence of such reservoirs. The major role of heavy fractions, especially asphaltenes, has been shown in various ways, whereas low-boiling-point cuts (< 350 °C) were not able to induce wettability changes. Moreover, it appears that, among intermediate fractions of a crude oil, some may change the surface properties of rocks, depending on the type of rock. Our research also confirms that various pure-acid and basic-organic compounds with low molecular weight are not able to induce wettability changes in various kinds of porous media.