Quantifying the impact of surface roughness on contact angle dynamics under varying conditions

Abstract

Despite extensive research in recent years to clarify the role of fluid composition on reservoir wettability, understanding the properties of rock and its solid surface characteristics and their effects on wettability and its alteration remains limited and requires further investigation. This study utilized sandpaper with different roughness levels to examine the effect of roughness on the contact angles of n-heptane, crude oil (CO), brine, and deionized water (DW) with solid surfaces. In a DW-air-solid system, the measurements indicate that increasing the surface roughness beyond a certain point decreases the surface's affinity for the fluid. A similar trend was observed with the brine, although the contact angle values for the rough surfaces in contact with the brine were slightly higher than those for the DW. Increasing the surface roughness significantly decreases the contact angle between the solid and the crude oil droplet in a CO-air-solid system. In the n-heptane-air-solid system, the droplet completely spreads on the solid, regardless of the surface roughness. This variability underscores the importance of fluid-solid interactions. The CO-brine-solid system exhibits behavior similar to that of DW, with the brine generally resulting in higher contact angle values across all examined roughness levels. The examination of the contact angles for various fluids in the liquid-air-solid and liquid-liquid-solid systems shows that the contact angle depends on the mean surface roughness, the surface roughness profile, the chemistry of the fluids, and the type of fluid trapped between the droplet and the rough surface. The findings demonstrate that the effect of roughness on surface wettability cannot be interpreted solely based on the wettability of a smooth surface or the increased area due to surface roughness. The variation in the curvature of the trapped fluid can significantly influence the wettability of rough surfaces. These findings enable optimized oil recovery and flow management by demonstrating how surface roughness enhances wettability control improving oil displacement, reducing capillary trapping, and refining reservoir models. Additionally, they support engineered solutions for shale production and fouling prevention, significantly increasing operational efficiency across petroleum systems.

Keywords: Contact angle; Fluid composition; Heterogeneity; Surface roughness; Wettability.

Fig. 1

A schematic illustration of the contact angle measurement method for the liquid-air-solid system.

Fig. 2

Schematic of the advancing and receding contact angles.

Fig. 3

Schematic illustration of the contact angle measurement method for the liquid-liquid-solid system.

Fig. 4

Variation of the static, receding, and advancing contact angles as a function of the mean roughness for the DW-air-solid system under ambient conditions.

Fig. 5

Variation of the static, receding, and advancing contact angles as a function of the mean roughness for the brine-air-solid system under ambient conditions.

Fig. 6

Variation of the static, receding, and advancing contact angles as a function of the mean roughness for the CO-air-solid system under ambient conditions.

Fig. 7

Variation of the static contact angle as a function of the mean roughness for the CO-DW-solid system under ambient conditions.

Fig. 8

Variation of the static contact angle as a function of the mean roughness for the CO-brine-solid system under ambient conditions.

Fig. 9

Schematic representation of the droplet placement on a heterogeneous rough surface.

Fig. 10

Schematic representation of the curvature of the trapped fluid on the surface roughness for (a) non-wetting trapped fluid and (b) wetting trapped fluid.

Fig. 11

The effect of (a) pore radius (R), (b) fluid interface curvature (r_c), and (c) convergence angle of the pores (φ) on the contact angle of a rough surface.