Microfluidics-based analysis of dynamic contact angles relevant for underground hydrogen storage

Underground Hydrogen Storage (UHS) is an attractive technology for large-scale (TWh) renewable energy storage. To ensure the safety and efficiency of the UHS, it is crucial to quantify the H-2 interactions with the reservoir fluids and rocks across scales, including the micro scale. This paper reports the experimental measurements of advancing and receding contact angles for different channel widths for a H-2/water system at P = 10 bar and T = 20 degrees C using a microfluidic chip. To analyse the characteristics of the H-2 flow in straight pore throats, the network is designed such that it holds several straight channels. More specifically, the width of the microchannels range between 50 mu m and 130 mu m. For the drainage experiments, H-2 is injected into a fully water saturated system, while for the imbibition tests, water is injected into a fully H-2-saturated system. For both scenarios, high-resolution images are captured starting the introduction of the new phase into the system, allowing for fully-dynamic transport analyses. For better insights, N-2/water and CO2/water flows were also analysed and compared with H-2/water. Results indicate strong water-wet conditions with H-2/water advancing and receding contact angles of, respectively, 13 degrees-39 degrees, and 6 degrees-23 degrees. It was found that the contact angles decrease with increasing channel widths. The receding contact angle measured in the 50 mu m channel agrees well with the results presented in the literature by conducting a core-flood test for a sandstone rock. Furthermore, the N-2/water and CO2/water systems showed similar characteristics as the H-2/water system. In addition to the important characterization of the dynamic wettability, the results are also crucially important for accurate construction of pore-scale simulators.