Relationship Between Geomechanical Properties and Rock Wetting Behavior

Abstract

Abstract Although geomechanical properties primarily relate to the structural aspects of rocks, while wettability is predominantly associated with surface properties, there can be a connection or interrelation between these two aspects. Rock mechanical properties, including unconfined compressive strength (UCS), surface hardness, Young's modulus, and Poisson's ratio, can be correlated to rock wettability via contact angle measurements through various interconnected mechanisms. This could be through fluid penetration and seepage which affect the ability of fluids to infiltrate the rock matrix. Moreover, mechanical properties are associated to porosity, permeability, and pore structure and connectivity of rocks which could also affect wettability. Overall, the relationship between geomechanical properties and wettability is intricate and requires comprehensive investigation. Therefore, in this work, we investigated the relationship between geomechanical properties and rock wettability via contact angle and Amott index. Both sandstone and carbonate samples were assessed. The contact angle measurements were conducted at reservoir temperature (353 K) and pressures (0.1 to 50 MPa) using drop shape analyzer, and the wettability results were compared with Amott tests under similar conditions. The findings indicate a correlation between the wetting behavior of the rocks, as measured by the contact angle, and its mechanical properties. Rocks with lower values of UCS, surface hardness, and Young's modulus tend to have higher values of Poisson's ratio, leading to lower contact angles and a more water-wet behavior, suggesting an interconnection between these properties. However, the Amott index does not indicate this relationship. In addition, increase in pressure causes a slight reduction in the contact angles observed in the oil/brine/rock systems. Thus, understanding the relationship between rock mechanical properties and wettability requires considering the combined influence of fluid penetration, and geomechanical and stress-induced effects. It is essential to integrate these factors to gain comprehensive insights into the complex behavior of fluid-rock interactions and its implications for various geological and engineering applications.