The role of nitrogen and sulphur bearing compounds in the wettability of oil reservoir rocks: an approach with nuclear microanalysis and other related surface techniques

Oil recovery is strongly influenced by the wettability of the reservoir roc k. Some constituents of the crude oil (polar compounds and heavy fractions such as asphaltenes with heteroatoms) are believed to react with the reserv oir rock and to condition the local wettability. Therefore, it is important to obtain as much knowledge as possible about the characteristics of the o rganic matter/mineral interactions. This study is devoted to the descriptio n at the microscopic scale of the distribution of some heavy fractions of c rude oil (asphaltenes) and nitrogen molecules (pyridine and pyrrole) on mod el minerals of sandstone reservoir rocks such as silica and clays. Nuclear microanalysis, X-Ray Photoelectron Spectroscopy and other related microscop ic imaging techniques allow to study the distribution and thickness of the organic films. The respective influences of the nature of the mineral subst rate and the organic matter are studied. The important role played by the n itrogen compounds in the adsorption of organic matter is emphasized. (C) 19 99 Published by Elsevier Science B.V. All rights reserved.