Characterizing thermal runaway of reservoir rocks under electromagnetic irradiation towards hydrogen generation from petroleum reservoirs

•Fundamental interactions of reservoir rocks and microwave are investigated.•Chlorite, albite, and illite are identified to facilitate thermal runaway (TR).•The phase transformation of quartz contributes to the occurrence of TR in sandstone.•TR results in 50.0–66.7% and 64.0–80.0% power saved for heating sandstone and shale rocks. Electromagnetic(EM)-assisted catalytic heating presents a novel method for in-situ hydrogen production from petroleum reservoirs. This study delves into the interaction between electromagnetic waves and reservoir rocks, characterizing the fundamentals behind thermal runaway (TR) phenomenon in sandstones and shales. Utilizing a custom microwave reactor and advanced analysis techniques, we identify the microwave-induced thermal runaway phenomenon in San Saba sandstone rocks at ∼ 568 °C and Mancos shale rocks at ∼ 253 °C, emphasizing the role of mineral, elemental compositions, and dielectric properties in these differences. We also identified that chlorite, albite, and illite are major contributors to thermal runaway and the significant reduction in power required for reheating rocks, saving 50.0–66.7% for sandstone and 64.0–80.0% for shale. This work contributes new insights into the occurrence and mechanisms of thermal runaway in reservoir rocks, therefore providing an efficient way for enhancing heating efficiency and reducing energy input for in-situ hydrogen production. This research further de-risks the emerging technology for in-situ hydrogen production from petroleum reservoirs via electromagnetic-assisted catalytic heating.