Abstract and subjects
Geologic storage of CO2 and H2 are climate‐positive techniques for meeting the energy transition. While similar formations could be considered for both gases, the flow dynamics could differ due to differences in their thermophysical properties. We conduct a rigorous pore‐scale study of water/CO2 and water/H2 systems at relevant reservoir conditions in a Bentheimer rock sample using the lattice Boltzmann method to quantify the effects of capillary, viscous, inertial, and wetting forces during gas invasion. At similar conditions, H2 invasion is weaker compared to CO2 due to unfavorable viscosity ratios. Increasing flow rate, however, increases the breakthrough saturation for both gas systems in the range of capillary numbers studied. At isolated conditions of flow rate, viscosity ratio, and wettability, local inertial effects are found to be critical and show consistent increase in the invaded gas saturation. The effect of inertial forces persits for both gases across all field conditions tested.
Plain Language Summary
We present a numerical investigation at the pore‐scale to contrast the dynamics of fluid transport for water/CO2 and water/H2 systems at reservoir conditions. Understanding such dynamics is critical to evaluate the feasibility of the geologic storage of these gases (long‐term storage of CO2 and short‐term, periodic storage of H2), which are being researched as green techniques for mitigating climate change. Through a systematic analysis, we demonstrate the importance of pore‐scale mechanisms like local inertial effects which are not well studied in the literature. These effects cause fast fluid motion and consistently allow more fluid to be injected in the rock independently from the other physical effects. Such effects should be carefully accounted for when modeling these systems for large‐scale gas storage.
Key Points
At similar reservoir conditions, invasion of H2 is found to be weaker as opposed to CO2 due to unfavorable viscosity ratios
Among the tested reservoir scenarios, P/T conditions for the saline aquifer provided the largest amount of invaded gas until breakthrough
Local inertial effects control the dynamics of the invading gas across different wettability, viscosity ratios, and capillary numbers