Determination of reservoir rock wettability by thin layer wicking approach

The present study was an attempt to investigate the possibility of contact angle determination of two immiscible fluids in contact with the solid surface of a porous material with heterogeneous mineralogical composition. Since the contact angles are measured on a single mineral's crystal, the question of how representative the results of wettability of the rock containing many different constituents arise. Due to the roughness, heterogeneity, and absorption ability of porous surfaces of reservoir core, the direct measurement of contact angle is not applicable. When contact angles cannot be directly measured, the measurement of capillary rise in a bed of particles can be used to quantify wetting characteristics of the solid. The main objective of this study was to investigate the determination of rock wettability by Thin Layer Wicking approach. The application of the Washburn equation for dynamic measurement of contact angle and the method of Thin Layer Wicking were described. Experiments were conducted on the powdered samples of different sandstone and limestone rock samples and also their representative pure minerals such as quartz and calcite, respectively. As a wicking test liquid, distilled water, 2% NaCl brine, kerosene, and mineral oil were used, and their contact angles with respect to the sample's solid surface were calculated. Powdered sample of quartz mineral was proved to be more water-wet than powdered sample of calcite mineral. Furthermore; the contact angle values of carbonates are closer to that of calcite while the contact angle values of Berea and Bentheim sandstone are closer to that of quartz. This study is the first Thin Layer Wicking study in Petroleum and Natural Gas Engineering Field, and it can be a leading survey to attempt new investigations in this subject.