Effect of Pressure on Wetting Properties of Crude Oil, Sandstone Rock, Water, CO2 and (or) Flue Gas System

Abstract

Carbon dioxide injection, either miscible or immiscible, has been known as an efficient strategy to enhance oil recovery as well as reduce CO2 emission. Wettability has a significant effect on the performance of enhanced oil recovery techniques because of its effect on fluid saturation distribution and flow behavior in porous media. For oil-wet rock, CO2 must overcome a capillary barrier to invade the rock matrix in order to be able to displace the oil in a secondary drainage process. If the rock wettability alters from oil-wet to gas-wet, a positive value of capillary pressure is established. Therefore, the injected CO2 will spontaneously imbibe from the fractures into the matrix blocks and oil will be expelled. This study describes the contact angles, i.e., wettability, in systems with water, an oil-saturated rock, carbon dioxide and/or synthetic flue gas. Experiments were carried out at pressures varying between 0.1 and 16.0 MPa in a pendant-drop cell that can determine bubble shapes and contact angles. Two situations are considered: rock-system I is partially water-wet, whereas rock-system II is effectively oil-wet. The experiments show that contrary to results obtained previously with CO2 (Ameri et al. 2013), flue gas cannot become the wetting phase.