To obtain a complete maturation set of strictly same precursor, an oil-prone tertiary coal from the Mahakam delta (Indonesia) is submitted to artificial maturation using confined pyrolysis; The analysis of the co-genetic phases (free hydrocarbons, resins, asphaltenes, and residual kerogen) reveals the composition and evolution of each fraction. It appears; that the polars have a high oil potential and contribute significantly to the generation of hydrocarbons (up to 25% of the initial oil potential, and up to 50% at given maturation stages). During the main stage of bitumen generation, a great part of the initial oil potential is thus transferred to the polars. During the later stages of thermal breakdown, this potential is released and contributes to the generation of aliphatics. In addition to their contribution as hydrocarbon source, the polars of the Mahakam coal contain a significant amount of Dammar resin. This latter is revealed to be a source of hydronaphthalenics which are very efficient hydrogen donors. Thus, the polars also appear to be a significant source of hydrogen available to organic reactions. It is postulated that one important condition allowing the generation of oil from coal is the presence of abundant resins, similar to Dammar resin, able to yield hydronaphthalenics during maturation. These compounds avoid cross-linking of the coal structure and participate in the formation of a free-flowing oil. On the contrary, in the absence of resin able to liberate hydronaphthalenics (or if the quantity of such resin is too low) the formation of oil is hindered, despite the good quality of all other parameters (aliphaticity and hydrogen richness of the coal, geological setting, expulsion capabilities, etc.). During further maturation in-situ cracking of the bitumen occurs, leading primarily to the formation of gas and not of oil.