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

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.

Reservoir geochemistry: methods, applications and opportunities

“…They are also the species involved in the formation of emulsions with waters during production (Acevedo et aL 1992). Through adsorption onto mineral surfaces, NSOs may affect reservoir wettability (Cuiec 1977(Cuiec , 1984Crocker & Marchin 1988;Dubey & Waxman 1989;Clementz 1976). Finally, some NSOs, such as phenols (or even the hydrocarbon benzene), are significantly water-soluble (Table 3) and may be depleted from petroleum during secondary migration.…”

“…The asphaltenes appear to have slightly longer average n-alkyl chain lengths than resins or aromatic hydrocarbons (Wilhelms & Larter 1995). Adsorption of resins/asphaltenes on mineral or reservoir surfaces has been demonstrated from model systems by Cuiec (1977Cuiec ( , 1984, Dubey & Waxman (1989), Trabelsi (1987) and Crocker & Marchin (1988), but it would appear that the surface films in reservoirs are actually enhanced in organic nitrogen compared even to asphaltenes. This suggests that subsets of these fractions are adsorbed.…”

“…This suggests that subsets of these fractions are adsorbed. Cuiec (1977Cuiec ( , 1984 has demonstrated that both mineralogy and oil composition control adsorption of NSOs on reservoir surfaces.…”

“…No separate gas phase is present into which petroleum components may partition (Thompson 1988;Larter & Mills 1992). Studies of the restoration of cores for laboratory core analysis (Cuiec 1977) and of the rate of partition of petroleum compounds from oil spills into water (Southworth et al 1983 13. Composition of carbazoles in associated source-rock extracts and reservoired petroleums.…”

Experimental Investigation into Effects of Crude Oil Acid and Base Number on Wettability Alteration by Using Different Low Salinity Water in Sandstone Rock

“…First, the polar components present in the oil phase may be ionized depending on the pH value. The ionization of basic material results in positively charged crude oil components; while the ionization of acidic material results in negatively charged crude oil components 12) . These hypotheses are important in understanding the system described below.…”