Nowadays, climate change is a significant issue due to the escalated combustion of conventional fossil fuels, such as coal and petroleum. In order to reach the 1.5 °C temperature goal proposed by the Paris Climate Agreement, “Carbon Peak” and “Carbon Neutrality” have become the most challenging social, environmental, and economic issues for most countries, especially for developing countries like China and India. Therefore, it is vital to develop low carbon to zero-carbon energy technology to retain the energy supply and reduce CO2 emissions effectively. Unconventional geo-energy sources such as geothermal energy (including hot-dry rock), shale gas, and natural gas hydrate are the primary sources of low carbon fuels compared to coal and petroleum. At the same time, CO2 geological utilization and sequestration (CGUS) is a promising frontier technology in pioneering such unconventional geo-energy extraction methods. CO2 utilization and sequestrationHowever, we have unsolved technological problems in developing unconventional geo-energy, CO2 sequestration, and reduced CO2 utilization. First, advanced technologies for stimulating tight and low permeability reservoir rock of shale gas and deep geothermal reservoir using water or supercritical CO2 is still an emerging topic of interest. Secondly, understanding the flow of natural gas, water, and CO2 in the natural or stimulated, complex rock fracture networks is essential for enhanced oil/gas recovery, heat extraction, and CO2 s...