Small quantities of a large variety of organic compounds enter the Recent marine sediments before burial. Petroleum, the only major organic and fluid substance in the consolidated rocks, however, contains mainly

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hydrocarbons. Experiments indicate that hydrocarbon compounds may travel through the sediments with the least restraint during intrastratal fluid flow. Most of the non-hydrocarbon compounds may be removed from the flowing phase by a selective filtration, i.e., chromatographic process.

Chromatography is a physical-chemical method of separation of fluid mixtures in which the components to be separated are distributed between two phases. One is a stationary phase of a large surface area and the other one is the fluid phase that percolates through the stationary phase. Fine-grained mineral particles, organic inclusions and (or) immiscible liquid droplets in sedimentary rocks may constitute the stationary phase. The Martin and Synge chromatographic theory is applied for tracing fluid flow through the sedimentary rock strata.

Petroleum contains colloidal particles, some of which are too large to have flowed through the smaller pore openings. Experiments show that oxidation and some other chemical reactions, taking effect after accumulation, may be responsible for the development of a part of the petroleum colloids. A regional study of the distribution patterns of organic constituents, combined with geological and geophysical data, can be useful information to the exploration geologist.

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