技術情報とプレゼンテーション

Contact angle hysteresis is an important physical phenomenon, it is an essential parameter in wetting and capillarity, and it plays an important role in many industrial processes, especially in Enhanced Oil recovery (EOR). In this paper, the contact angle hysteresis (CAH) of microdroplets on chemically heterogeneous substrates with different wettabilities was studied using a conservation level set method simulations, we developed a multiphysics multi-flow numerical model using COMSOL Multiphysics^® to predict the evolution of a droplet falling on a solid substrate. Our numerical model is applied to carbonate rocks which account for more than half of the world’s hydrocarbon reserves. Despite the complexity of carbonate rocks mineralogy, it is important to understand the fundamental phenomena responsible for the distribution of reservoir fluids, the developed model was applied to a carbonate sample using all input data from the experimental work carried out on carbonate rock samples, and the sample has 2 distinct phases: Calcite and Dolomite. The results showed that the dolomite is relatively more hydrophilic than the calcite sample.

This numerical model simulates the dynamic process of a water droplet impinging onto a carbonate substrate using the CFD Module of COMSOL Multiphysics^®, a finite element based software, coupled to the level set method for tracking the free surface between phases, with the presence of dolomite and calcite. The numerical coupled system was solved in COMSOL  Multiphysics^® 5.1 using Laminar Two-Phase flow, Level Set interface. Two contact angle models were considered and implemented into the developed multiphysics numerical model for two different surfaces with different degree of hydrophobicity (dolomite and calcite), and the simulation results were compared to study the effects of the solid wettability on the impingement process (contact angle hysteresis).

This model has been also considered to study the apparent contact angles for microdroplet on chemically heterogeneous surfaces formed regularly and randomly by two different patches of dolomite and calcite. In those cases, Young's equation no longer works, and instead, the Cassie model or Wenzel model is usually used to calculate the contact angle. However, in this work, we demonstrate that the Cassie equation is no longer valid if the dimension of droplet is larger compared to the size characteristic of the solid substrate heterogeneities. In this study, image analysis software is used in order to calculate the apparent contact angle as a function of the surface heterogeneity. It has been found that a dynamic contact angle model is important for accurately modeling the droplet spreading and receding process. The instantaneous evolution of the dynamic contact angle cannot be represented by a constant static contact angle or the advancing-receding static contact angles. The simulation results can provide a good understanding of the carbonate rock dynamic impingement process and provide insights on how the carbonate rock surface mineralogy and heterogeneity can affect the contact angle hysteresis. These findings aim to enhance our understanding of the mechanism of the CAH at the microscale and could help the oil industry to develop a new methods for enhanced oil recovery (EOR).