Comparative Study of Asphaltene Adsorption on Formation Rocks under Static and Dynamic Conditions

Abstract

AbstractSpecific adsorption of asphaltene from light, medium and heavy oils were determined on reservoir rocks having different calcite and clay contents. Pure calcium carbonate and montmorillonite were used as a basis of comparison. Static and dynamic asphaltene adsorption tests were performed for comparison. The dynamic tests were carried out on crushed reservoir rocks. The batch type measurements served for determination of the adsorption isotherms and kinetics of sorption. The effect of asphaltene adsorption on wettability was also investigated by contact angle measurements on homogeneous and heterogeneous rock plates.Based on the experimental results it was concluded that there is no significant difference in the adsorption of different asphaltenes: depending on the mineralogical composition the adsorbed amount changed between 2 and 5 mg/g (18 and 45 mg/m2). A well-defined correlation was obtained for the effect of calcite and montmorillonite: the adsorbed amount increased with the clay content, while the carbonate content decreased the adsorption loss. Under static conditions, the adsorption of asphaltenes in low concentration range could be described by the Langmuir and the Tóth isotherms, while in the high concentration ranges the declining trend of isotherms suggests a competitive process. The existence of competitive and consecutive processes is well demonstrated by the cumulative curve of adsorbed amount obtained by dynamic adsorption tests. The experimental results proved the composite, multicomponent character of the asphaltenes and the role of asphaltene concentration in the wettability alteration process.