THE UNDERGROUND MIGRATION OF OIL AND GAS 
THE PROBLEM 
KIRTLEY F. MATHER 
A necessary antecedent to the flow of oil or gas in commercial 
quantities into a drill hole is the concentration of a considerable 
amount of volatile hydrocarbons in a small space under condi- 
tions suitable to its ready release. There is much evidence for 
the belief that a very great percentage of the world’s petroleum 
and natural gas has originated in the midst of finely divided 
sediments, the muds, oozes, clays and shales. It is also apparent 
that oil and gas wells, with few exceptions, derive their valued 
products from the midst of comparatively coarse-grained sands 
and sandstones or from the larger crevices of limestones and 
shales. Disseminated broadly through fine grained sediments, 
the hydrocarbons are valueless, except in so far as they may 
be removed by expensive treatment of the rocks. Concentrated 
in limited portions of sand or sandstone, these same compounds 
become one of the most valuable sources of energy and power 
available to man. The history of oil and gas particles from the 
time of their origin to the moment when they enter the casing 
of a well is not only interesting; a knowledge of it is essential 
to the application of geology to the oil and gas industry. The 
ability to determine the probable location of new fields in ad- 
vance of drilling and the most favorable directions of extension 
of existing fields depend on a clear understanding of the laws 
governing the movement of hydrocarbons through the rocks 
and of the conditions which control the action of those laws. 
This movement seems to comprise two phases, of differing 
nature and presumably therefore resulting from different causes. 
The first of these is the migration of oil and gas out of the fine- 
grained source rocks into the coarser-grained sediments. This 
results in the segration of the available hydrocarbons in ‘‘sands.” 
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