172 University Geological Survey of Kansas. 
themselves in the order of their specific gravity. This would 
put the gas at the top of an arch, with oil next below and water 
still farther down. If, now, the supply of gas is sufficiently 
large it may occupy the entire arch extending away down the 
sides or limbs of the anticline. If, however, the supply of gas 
should be small, with oil in comparative abundance, the gas 
would be at the top of the arch, oil next below, and water still 
below the oil. 
CCL RKQWQY 
Z ek ee GW 
Z Spa 
ALAA ELLE LEZ LSS N 
LE 
° 
rx 
AD 
Vig. 5. Showing how gas, oil and water may be in the same sand and how each may 
be tapped by a well. 
Figure 5 will serve as a diagram illustrating how such con- 
ditions can be brought about and how wells put down in the 
several different places, as shown, may encounter several differ- 
ent conditions. Jn each case it will be understood that should 
oil be absent gas will lie immediately above the water. Should 
a well strike gas under these conditions with oil below the gas, 
after the latter is exhausted oil will enter the well, and may be- 
come very profitable. The last stages of either oil-well or gas- 
well probably will be that of a well filled with water. 
If nature by acting upon a bed of sandstone originally hori- 
zontal in position should throw it into the form of a gentle 
arch, the axis of the arch trending parallel with a mountain 
range, such an anticlinal arch may become exceedingly pro- 
ductive of either oil or gas, but particularly the latter. It 
sometimes happens that the direction of one of these arches 
practically coincides with the direction of an old ocean beach 
along which pure, clean sand was gathered, producing a porous. 
sandstone capable of holding large quantities of oil or gas. 
Such a condition produces the best known wells—those of the 
tremendous capacity of the Appalachian region. Large moun- 
tain ranges are not an essential for this condition, because we 
may have gentle swells in level countries where all the essential 
conditions are produced as above explained. Such is the case 
in the great eastern Indiana gas-fields. Here a gentle swell or 
arch in the Trenton limestone has been one of the main factors 
