Abstract

Underground hydrogen storage and carbon dioxide capture and sequestration in geological formations present a prominent solution for a low carbon economy. One of the main trapping mechanisms of the injected gas is the capillary residual entrapment controlled by the wettability characteristics of the reservoir rock. In the literature, there is a scarce of information about the influence of key parameters such as pressure, temperature, and organic content on the storage security. The present work discusses a fundamental capillary-based analysis using Laplace and Young equations to understand the interfacial characteristics of the gas–brine- rock system using experimental contact angle measurements of quartz and calcite samples conducted over a wide range of pressures (5, 10, 15, and 20 MPa) and temperatures (308°K, 323°K, and 343°K) using relevant reservoir brine. The analysis was carried out using typical pore throat radii (1μm) at the up-mentioned reservoir conditions. Furthermore, a correlation for the gas column height as a function of the reservoir pressure and temperature are developed. These results help for better understanding the reservoir efficiency for secure storage of H2 and CO2.

Introduction

Geo-storage technologies have been suggested as a method to store and withdraw large quantities of H2 and CO2. The geologic formation is one of the options that provide a large storage capacity. Structural trapping is the primary mechanism that holds H2 and CO2 in the subsurface geologic formations. The structural trapping is affected greatly by the capillary forces and the pore radius of the formation rocks. The capillary forces, in their turn, depend on the pressure and temperature of the subsurface geologic formations. Therefore, it is vital to assess the effect of these parameters on the storage capacity of H2 and CO2 via structural trapping under given geothermal conditions. Quartz and calcite rocks are among the most common rocks in underground formations. Hence, they are considered in the present study. This work would help in economical industrial-scale prediction of underground storage in the considered rock formations.

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