Colloids and Surfaces A: Physicochem. Eng. Aspects 241 (2004) 335–342 Compositional effects of fluids on spreading, adhesion and wettability in porous media Chandra S. Vijapurapu, Dandina N. Rao ∗ The Craft and Hawkins Department of Petroleum Engineering, Louisiana State University, 3516 CEBA Bldg., Baton Rouge, LA 70803, USA Available online 25 May 2004 Abstract The interfacial phenomena of spreading and adhesion of fluids on rock surfaces have serious implications because of their impact on produc- tion strategy and oil recovery. The present study reports new experimental data on the effect of brine dilution and surfactant addition on spreading and adhesion behavior of Yates crude oil on dolomite surfaces. Spreading and adhesion have been characterized through measurements of oil–water interfacial tension (IFT) and dynamic (water-advancing and receding) contact angles. The interfacial tension was measured using computerized axisymmetric drop shape analysis (CADSA) technique, which was calibrated against the well-known du Nuoy Ring technique. The dual-drop dual-crystal (DDDC) technique and the Wilhelmy plate technique have been used to measure dynamic contact angles. In order to study the effect of brine dilution, Yates reservoir brine was mixed with deionized water (DIW) in various proportions. The oil–water IFT initially decreased as the volume percent of brine in the mixture decreased but IFT increased with further dilution of reservoir brine with DIW. A decreasing trend was observed in the behavior of water-advancing contact angle with brine dilution. However, a strange behavior of spreading of crude oil drop against brine on the dolomite surface (with large water-receding contact angles) was observed at certain brine dilutions. This spreading of crude oil appears to be related to interfacial tension in a manner similar to Zisman’s observations in solid–liquid–vapor systems. The use of surfactants to enhance oil recovery through reduction in IFT is well known in the industry. However, this study examines the capability of certain surfactants to alter wettability in addition to reducing IFT. For the Yates reservoir rock-fluids system, an ethoxy alcohol surfactant altered the strongly oil-wet nature (advancing angle of 158 ◦ ) to water-wet (advancing angle of 39 ◦ ) at a concentration of 3500 ppm. While the DDDC technique yielded significant changes in wettability due to surfactant addition, the Wilhelmy Plate technique remained insensitive throughout the range of surfactant concentrations. The practical significance of this study is that it identifies two simple modes through surfactant addition and brine dilution to alter wettability to minimize capillary trapping of oil. © 2004 Elsevier B.V. All rights reserved. Keywords: Spreading; Wettability; Adhesion; Interfacial tension; Contact angle; Brine composition; Surfactants 1. Introduction The primary and secondary oil recovery processes cur- rently being practiced have been successful in recovering only about a third of the original oil in place leaving behind nearly two-thirds as residual oil. This points out the need to study and implement new and innovative methods to recover the remaining oil. This in turn requires an understanding of the interactions that take place between crude oil, brine and the rock surface, which are collectively represented by the term wettability. ∗ Corresponding author. Tel.: +1-225-578-6037; fax: +1-225-578-6039. E-mail address: dnrao@lsu.edu (D.N. Rao). Reservoir wettability is affected by several factors includ- ing roughness and mineralogy of the rock surfaces and the compositions of brine and crude oil. The effect of rock min- eralogy and surface roughness have been reported previously [1] and this paper presents the effects of fluid characteristics, namely brine dilution and surfactant addition, on spread- ing and wettability as characterized by water-receding and water-advancing contact angles, respectively. 1.1. Effect of brine composition on wettability Several previous studies have been reported in the liter- ature that describes the effect of brine composition on for- mation damage and waterflooding. Mungan [2] investigated the role of pH and salinity changes on core damage. He 0927-7757/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2004.04.024