UNDERGROUND MIGRATION OF OIL AND GAS 
179 
covering; (d) expulsion of juvenile water from igneous masses 
during crystallization; (c) expansion of gas which may be either 
of abyssal origin or newly formed by pressure upon organic 
materials at moderate depths. 
Washburne infers 
a small, but locally active, very slow, outward creep of the rock fluids 
(liquid or gas or both) due to pressure from below. The principal 
reason for the inference is based on plotting the distribution of pres- 
sures in the sands of different flelds of the United States and of Canada 
for which data are available. The data are not sufficiently complete 
to warrant final conclusions, bufc there are many instances in which 
the downward increase of pressure between sands, and the increase 
above the surface pressure, exceed the corresponding hydrostatic 
head It seems significant that excess pressures are most 
common in the more fractured regions, such as Baku and the Gulf 
Coast, where the deep communication appears to be more open than 
elsewhere. Other arguments for this ascent are found in the excess 
temperatures in oil fields, in the distribution of oils and gases of filtered 
and unfiltered types, in the excess of chlorine in the associated water, 
and in the abundance of helium in the deep wells of Kansas. 
Effect of movement upon accumulation of oil 
The chief contribution of ground water circulation to the 
underground accumulation of oil and gas in commercial quanti- 
ties is probably made as a conditioning rather than as a causal 
agent. Movement of subterranean fluids may assist in over- 
coming the adhesion and inertia of oil globules, which might 
otherwise prevent differences in specific gravity from accom- 
plishing gravitative sorting. Johnson^^ states, for example, 
that differences in specific gravity, and in capillary action seem 
remarkably impotent when everything is at rest, but that as- 
sisted by a little movement these differences bring about very 
important results. If oil-soaked sand is placed in the middle 
of a horizontal tube and w^ater-soaked sand is placed at either 
end, the tube may remain at rest a very long time without any 
27 Washburne, loc. cit., p. 956. 
28 R. H. Johnson, Discussion of Capillary concentration of gas and oil, Am. 
Inst. Min. Eng., Trans., vol. 50, pp. 842-843, 1915. 
