The newly developed methods of geochemical exploration will undoubtedly play an important role in exploration for oil and gas fields. There has been a tendency in this country among the explorers for oil and gas to undervalue the role of surface evidences of such deposits. Most of the great oil fields of the world have been indicated by surface evidences. In view of the prevalence of visible oil and gas seeps it is reasonable to expect to find microscopic seeps in much greater abundance. In practically all cases maximum leakage occurs from the edges of accumulations. These leaking gases are adsorbed by the earth particles near the surface and are then polymerized to the heavier hydrocarbons. The gases in leaking to the surface transport quantities of subsurface waters and the dissolved minerals, resulting in many cases in high mineral concentrations near the surface.

The data of geochemistry have led to some very interesting speculations regarding the genesis of oil and gas fields. Evidence strongly suggests that oil and gas fields result from the polymerization of the migrating hydrocarbon gases. Two sources of such gases have been measured, namely, vegetable matter that is being devolatilized and the basement rocks. There may of course be others as yet unmeasured. The important consideration is that so far as migration is concerned the gases are the principal participants.

It is believed that the oil accumulations and the concentrations of adsorbed hydrocarbons in the soil and in the oil shales are genetically related. As the principal difference between marine and non-marine sediments is the presence of sodium chloride (not organic content according to Trask), and as this will act as a catalytic agent to polymerize the hydrocarbon gases, it is reasonable to suppose that this is why oil fields occur in marine rather than non-marine sediments. Experimental laboratory investigation verifies this.

If one goes back far enough in point of origin of the organic gases either in the buried vegetable matter or the basement rocks both origins would immediately become inorganic. In view of this can it be said that there has ever been an organic theory of the origin of oil and gas?

On the basis of the hypothesis proposed it is possible to explain the difference in mineralization of subsurface waters in different geologic provinces, as well as the relation between volatility of accumulations as a function of the carbon ratio (rock deformation) and overburden. Caliche may owe its existence to the transporting power of the vertically migrating gases.

It should be kept in mind the method of geochemical exploration is not predicated on the theoretical conceptions here presented. Rather, the reverse is true, in that the theory is derived from the data of geochemistry.