Iron-sandstone synergy: Advancing in-situ hydrogen production from natural gas via electromagnetic heating

Abstract

To address the escalating demands for decarbonization in the petroleum industry, a carbon-zero technology, known as in-situ hydrogen (H2) production via electromagnetic (EM)-assisted catalytic heating, has recently been proposed for generating and extracting clean H2 directly from petroleum reservoirs. Although preliminary techno-economic analyses show significant potential of this emerging technology for clean and affordable hydrogen, the fundamentals of natural gas conversion to H2 in the presence of reservoir rocks are poorly understood. In this study, we explore the synergy between sandstone and artificial iron-based catalysts in enhancing in-situ H2 production from methane (CH4) cracking under EM irradiation. The dynamic behaviors of sandstone under EM heating are comprehensively investigated, including its thermal behaviors, thermal runaway (TR) phenomenon, gas generation during TR, and energy consumption. We found that sandstone demonstrates an evident natural catalytic effect for promoting CH4 conversion to H2, enabling H2 production starting at about 394 °C. The natural catalytic role of iron minerals in sandstone is elucidated using various advanced characterization techniques. Remarkably, when adding iron catalysts into the sandstone, the highest H2 concentration and CH4 conversion reaches 91 mol.% and 80%, respectively, at a temperature of 666 °C, while they are 50 mol.% and 35%, respectively, for the sample consisting of iron catalysts and quartz at the same level of temperature. This result indicates a strong iron-sandstone synergy and a potential to stimulate H2 production by leveraging this synergy. Throughout the experimental process, the generation of carbon oxides (CO and CO2) is negligible. These findings pave a pathway towards future pilot for carbon-zero in-situ H2 production from sandstone gas reservoirs.