We investigate smart methodologies to know and control large sc ale fluid flow in subsurface at few km deep, and we apply the methodologies to solve the problems on earth environment and energy. Our works are currently focusing on (i) CO₂ geological storage as a means of climate change mitigation, (ii) geothermal energy which is renewable and abundant in Japan, and (iii) methane hydrate seated below deep sea floor, which is expected to be a next-generation energy resource to replace oil and natural gas.