Hydrogen wettability of quartz substrates exposed to organic acids; Implications for hydrogen geo-storage in sandstone reservoirs

Hydrogen is presently evaluated as a clean fuel to mitigate anthropogenic CO2 emissions and reduce the greenhouse gas effect. However, one of the major challenges for implementing a full hydrogen economy is hydrogen storage (as hydrogen is highly volatile and compressible). The solution to this problem is storing hydrogen into geological formations (as they are abundant and have large storing quantities). One of the key factors in this process is the wettability of the formation, which determines fluid dynamics, containment security, withdrawal rates, and storage capacities. To do this, we have determined the wettability of sandstone rock representative substrate through an extensive set of experiments in the presence of hydrogen. Whereas, almost all of these formations contains organic acids (hexanoic C6, lauric C12, and lignoceric C24 acids, respectively), even in minute concentrations, ranging from C4 to C26. Therefore, to fully comprehend the H2 wettability in a realistic scenario, we have aged quartz substrates in organic acids and conducted contact angle measurements under assorted storage conditions (temperature of 323 K, pressure of 0.1, 15, and 25 MPa). Our results show that pure quartz was inherently strongly water-wet (where θa is 40.8° and θr is 35.1°) and turned to intermediate water-wet (θa is 91.3° and θr is 82.7°) in presence of H2 (at 323 K and 25 MPa) when the rock substrate was aged with organic acids having longer alkyl chain (10−2 Molarity (M) of lignoceric acid). This study, thus, provides crucial information for the implementation of the future hydrogen economy.