Carbonate sedimentary systems, like modern coral reefs, belong to Earth external envelopes and form a unique interface between biosphere, hydrosphere, atmosphere and lithosphere that is in permanent physico-chemical disequilibrium. They consist in solid substratum, mobile or rigid, acting as a major carbon sink, with complex structures and heterogeneities at all scales. Understanding carbonate sedimentary systems consists in fact to study exceptional archives of the Earth System, from Precambrian to present day, including evolution of life, climate and sea level changes. The particular spatial relationships between organic and mineral carbon cycles in the context of global-regional geodynamic and climatic changes have resulted READ MORE... . in the preservation of more than 70 % of the global volume of conventional hydrocarbon in carbonate rocks. Managing and securing these important energy resources is becoming critical to support the forthcoming energy transition, but remaining reserves in these complex reservoirs are difficult to detect and predict. Future exploration and production of hydrocarbon from carbonate reservoirs, that would not rely any longer on massive industrial investments, will subsequently become increasingly risky from economical and technological view points. Paradoxically, a successful energy transition will require drastic improvements of our knowledge on carbonates to guaranty an economic hydrocarbon supply.