Two decades ago, Mexico reached the peak of oil production and 15 years ago that of natural gas. Since then, oil production has halved and gas production decreased by one third, while proven crude oil reserves are 26 % of those existing in 2004. Despite the obvious geological decline, the idea persists that the oil and gas sector is a fundamental part of the countrys' future. In this paper we present a review and critical analysis of the production and refining of hydrocarbons in recent decades, as well as some probabilistic scenarios of future production, to provide objective elements for discussion on the viability of a model based on fossil fuels. Our analysis indicates that in the past two decades Mexico has entered an irreversible process of diminishing returns, which implies an increase in energy and economic costs both in exploration and production and in refining, as well as a growing dependence on natural gas imports. The depletion of the giant fields offshore Campeche is being offset by a growing number of fields of much smaller size and rate of production and greater depth. Coupled with the need for enhanced recovery methods in mature fields this has steadily lowered the energy return on investment (EROI), which is currently less than half that of 2004. Consequently, although since 2019 the level of production has stabilized, the net energy available to society and to economy is decreasing, while energy and economic costs are increasing. In the refining sector, there is a growing deficit between national production and demand for gasoline and diesel, which is offset by imports. Despite a change in trend in the last three years, our analysis indicates that even refining all the oil produced in Mexico, the amount of gasoline produced would not be enough to satisfy the current level of consumption. On the other hand, the consumption of natural gas by PEMEX itself in the production and refining sectors has been growing until reaching 60 % of the national gas production. Paradoxically, the effort to reduce the import of refined products produces an increase in the import of natural gas, which already represents 70 % of the national demand. The probabilistic analysis indicates no chance of discovering more giant fields and that what remains to be discovered are mostly small or very small fields. The decline scenarios that we present, based on the historical behavior of reserves and production, adjust much better to actual behavior than those published in previous years by the Ministry of Energy. These scenarios indicate that by 2030 there would be a production of around 1.25 million barrels of crude oil per day, without considering the exploitation of unconventional resources. The latter, however, could only provide a temporary palliative to the decline in hydrocarbon production with a high environmental, energy and economic cost. Considering the growing socio-environmental impact and the effects on the climate of the production and consumption of fossil energy, it is necessary to think about a de-escalation of the oil activity, formulating a plan for a gradual exit from the dependence on fossil fuels that necessarily implies a decrease in energy consumption.
