The exhaustible resources and specifically liquid hydrocarbons in situ, are considered as a patrimony of a nation-state because they are assets that can be inherit from one generation to another, and it is convenient to find a social optimal exploitation between generations. In this paper a quantitative valuation is carried out about oil wealth. This valuation begins with the amount of proved oil reserves that was in situ in Mexico the years of 1979 and 2011. To achieve this, it is necessary to calculate the present value of the expected profit margins during the productive life of resources. By other side, it has been developed a comparative analysis about the oil industry performance in Mexico and in world. The most relevant findings were: on the one hand, the continued decline in the volume of proven oil reserves in Mexico since 1982, against the continued increase in the world and, on the other hand, the accelerated decrease in the production of the Cantarell promissory complex.