A microscopic study of the effect of variable wettability conditions on immiscible fluid displacement

Abstract

This paper presents the results of attaicroscopic investigation of immiscible fluid.behavior under variable wettability conditions. Seventeen waterfloods were conducted in a mono-layer glass-bead flow cell under water-wet,.neutral-wettability, oil-wet, and wettabllity-reversal conditions. Quantitative production data were obtained for each flood. Also, a 16 mm film recording utilizing an arriflex camera was made during each flood test. Photographs taken from 16 mm film recordings are herein presented as being representative cf the microscopic and macroscopic behavior for the fluid systems studied. Residual oil structures Were visually defined as being noncontlriuous under water-wet conditions. Oil-wet conditions yielded both-continuous and noncontinuous type structures. The idea of residual oil continuity under oil-wet conditions is proposed as being responsible for increased oil production when going from an oil-wet to a water-wet condition. In all cases during these experiments where additional oil was recovered during a reversal flood, there was essentially continuity of the residual oil saturation following the con-ventional waterflood.under oil-wet conditions. It has been shown that, where residual oil continuity existed, oil mobility may be established from a transient change .in contact angle. An attempt has been made to define the mechanism responsible for this phenomena.