Organic fossil fuels are from sedimentary basin and the basin is a huge crude reactor, which should be a grand canonical ensemble. Formation and occurrence of organic fossil fuels should be treated with the principle of thermodynamics of non-equilibrium. In the basin, the distribution of organic fossil fuels is in accord with the distribution types of kerogen and the sedimentary sequence from lower animal and plant to higher plant. According to new hypothesis, heavy oil is to be located near the margin of basin; therefore, potential region will is many multiples of current regions.