Research Project CX7

 March 2024 - present

Wettability plays a crucial role in multi-phase flow in porous media as it controls the distribution of the fluid phases and their joint interfaces throughout the porous structure. As such, it is highly relevant in a wide range of environmental and engineering applications where interface driven processes are important; for example, water flow in the vadose zone, water and gas production during fuel cell hydrolysis, and subsurface gas storage. The apparent wettability of a liquid-gas fluid pair inside a porous medium can be characterized with the contact angle between the solid-liquid and liquid-gas interface and is different from the intrinsic contact angle measured on an ideal flat surface due to several factors including chemical and topological heterogeneities of the solid walls of the pores, the geometry of the porous network, and the forces acting on the system.

In this project, a novel high pressure, high temperature (HPHT) cell setup is constructed to characterize the wetting behavior of liquid-gas-solid systems under various driving forces for a wide range of pressure and temperature conditions.

A HPHT cell setup was developed in collaboration with the Porous Media Lab (research project Z02) to measure contact angles for both bubbles (captive bubble method) and droplets (sessile drop method) in contact with a solid substrate under controlled conditions (Figure 1). The solid substrate is positioned at the center of the cell, away from the front and back, ensuring a clear connection between the top and bottom of the chamber. The total volume of the cell is 7 mL. When a substrate is placed inside, the remaining volume is approximately 4.5 mL. It features five ports: an injection port, an outlet port, a temperature control port, a pressure control port, and an additional port that can be used for future relative humidity measurements. The setup incorporates three pumps: a gas pump, a liquid pump, and a backpressure pump for pressure regulation. A heating jacket surrounds the cell, enabling precise temperature control. The cell is mounted on a rotary table, allowing it to be tilted for advancing and receding contact angle measurements (tilted plate method). The current configuration can withstand pressures up to 12 MPa and temperatures up to 140°C. The imaging hardware consists of a Basler camera (acA5472-17 μm) capable of delivering up to 17 frames per second at a resolution of 5472 × 3648 pixels. It is equipped with a Nikon lens and a 45-degree optical prism. Image acquisition is performed using the Pylon software, while image processing and analysis are conducted using an in-house developed MATLAB code. The cell has been tested for the N2-water-quartz system for all different configurations (captive bubble, sesille drop, and tilted plate) for pressures up to 10 MPa and temperatures up to 100 °C.