Effects of Crude Oil Components on Rock Wettability

Abstract

Published in Petroleum Transactions, AIME, Vol. 216, 1959, pages 330–333.Paper presented at the AIChE-SPE Joint Symposium in Kansas City, Mo., May 17–20, 1959. Abstract The effects of crude oil components on the wettabilities of sandstone and limestone were investigated. Fractions containing components differing in molecular weight and molecular structure were obtained from crude oils by distillation, extraction and chromatography. Individual fractions were then tested for their effects on rock wettability. Tests indicate that sandstone wettability may be changed by a complex variety of surfactants varying both in molecular structure and molecular weight. Limestone appears to be particularly sensitive to basic, nitrogenous surfactants. Introduction Investigations in recent years have shown that petroleum reservoir rock wettability can exert a significant influence on the efficiency with which oil can be produced by water flooding. While most reservoirs are presumably water-wet, they may range in their degree of water-wettability from near-neutral to strongly water-wet. Reservoir wettabilities other than strongly water-wet are likely to be induced by adsorption of surface-active components from the crude oil on the pore walls of reservoir rock. Little is known, however, about the nature of the surface-active materials which are likely to be adsorbed by the reservoir rock. Due to the complexity of crude oils, attempts made in the past to isolate these surface-active components have met with only limited success. It is probable that many different types of surface-active materials are indigenous to crude oils and that many of these may be adsorbed to varying degrees by reservoir rock. This was explored in the studies discussed in this paper.