Compositional Dependence of Reservoir Wettability

Document Type

Conference Proceeding

Publication Date

1-1-2001

Abstract

The purpose of this work is to carry out a systematic study of the effects of crude oil, brine and rock compositions on formation wettability. Degree of wetting depends on the dynamic contact angle measured in a mode that enables movements of the three-phase contact line. Knowledge of formation wettability is important in primary, secondary, and enhanced oil recovery operations. By varying compositions of crude oil and brine, and using crystal surfaces of different mineralogy and roughness, we can get a better understanding of the rock-fluid interactions in reservoirs. The Wilhelmy Plate technique is being used in this study to measure adhesion tension (which is the product of interfacial tension and cosine of the contact angle) at the solid-liquid interface; a microbalance is connected to a computer which detects the change in force as the solid surface travels through oil and brine interfaces in advancing and receding modes. The water-advancing and water-receding contact angles can then be calculated from the adhesion tensions by making independent measurements of the fluid-fluid interfacial tensions. The method is used to study pure hydrocarbons and synthetic brines of different concentrations and the wetting behavior is used to study Yates field crude oil, brine and rock interactions. Polished surfaces of glass slides and dolomite are used to simulate the reservoir rock surface. An ethoxy alcohol surfactant, which is being used in the field for enhancing oil recovery, was used to quantify its wettability effects. The results of the systematic experimental investigation of the effects of practical variables on wettability are presented. It is found that interactions between surface active agents at the interface of two fluids have an effect on wettability alteration. The composition and concentrations of different organic and inorganic chemical species have a major effect in making a reservoir oil-wet or water-wet.

Publication Source (Journal or Book title)

Proceedings - SPE International Symposium on Oilfield Chemistry

First Page

755

Last Page

766

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