Finally, a word of caution on the essential fragility of a study on the very long-term future for the world's energy supply which accepts without question the validity of the original 18th century hypothesis that all oil and gas resources have been generated from biological matter in the chemical and thermodynamic environments of the earth's crust.
There is an alternative theory - already 50 years old - which suggests an inorganic origin for additional oil and gas. This alternative view is widely accepted in the countries of the former Soviet Union where, it is claimed, "large volumes of hydrocarbons are being produced from the pre-Cambrian crystalline basement". Recent applications of the inorganic theory have, however, also led to claims for the possibility of the Middle East fields being able to produce oil "forever" and to the concept of repleting oil and gas fields in the gulf of Mexico.
More generally, it is argued, "all giant fields are most logically explained by inorganic theory because simple calculations of potential hydrocarbon contents in sediments shows that organic materials are too few to supply the volumes of petroleum involved."
There have been numerous reports in recent times, of oil and gas fields not running out at the expected time, but instead showing a higher content of hydrocarbons after they had already produced more than the initially estimated amount. This has been seen in the Middle East, in the deep gas wells of Oklahoma, on the Gulf of Mexico coast, and in other places. It is this apparent refilling during production that has been responsible for the series of gross underestimate of reserves that have been published time and again, the most memorable being the one in the early seventies that firmly predicted the end of oil and gas globally by 1987, a prediction which produced an energy crisis and with that a huge shift in the wealth of nations. Refilling is an item of the greatest economic significance, and also a key to understanding what the sources of all this petroleum had been. It is also of practical engineering importance, since we may be able to exercise some control over the refilling process.
The debate about the origin of all the petroleum on Earth lies in the center of the subject. If we really knew that it is only biological materials, which, in their decay, could produce hydrocarbons, then the quantities that could ever be produced would be limited by the biological content of the sediments. But then the clear and strong association of petroleum with the inert gas helium would have no explanation; the finding of hydrocarbon gases, liquids and solids on most other planetary bodies in our solar system which have surface conditions quite unsuitable for surface life, could not be understood; the presence of hydrocarbons which we now find in abundance in basement rocks would also remained unexplained.