4 BBS WEATHERBY AND Ne eNO ts ie 
RESULTS 
SHALE AND SANDSTONE VELOCITIES 
The velocities for shale and sandstone from the surface to a depth 
of 2,000 feet are given in Table I. The velocity given for each age is 
an average of velocities obtained in several wells. The individual 
velocities followed the mean closely. 
TABLE I 
VELOCITIES IN SHALE AND SANDSTONE TO 2,000 FEET 
Age Velocity (Ft./Sec.) 
Devonian 13,300 
Pennsylvanian 9,500 
Permian 8,500 
Cretaceous 7,400 
Eocene 7,100 
Pleistocene-to-Oligocene 6,500 
Because of the presence near the surface of the weathered layer 
of rather indefinite extent, some question may exist as to the accuracy 
of these results. The effect of this surface layer is canceled out in the 
determination of differential velocities in sections below the surface. 
Thus there are no weathering effects in the data in Table II, which 
shows the differential velocities obtained in shale and sand sections 
for a section extending from 2,000 to 3,000 feet below the surface, 
and also for a section from 3,000 to 4,000 feet deep. There is also 
listed the percentage increase in velocity at the greater depth. 
TABLE II 
DIFFERENTIAL VELOCITIES IN SHALE AND SANDSTONE 
Age Velocity from Velocity from Percentage 
2,000 to 3,000 3,000 to 4,000 Increase 
eet Feet 
(Ft./ Sec.) (Ft./Sec.) 
Devonian 13,400 13,500 0.7 
Pennsylvanian II, 200 II, 700 4-5 
Permian 10,000 = = 
Cretaceous 9,300 10,700 15.0 
Eocene 9,000 10, 100 Toe 
Pleistocene-to-Oligocene 7,200 8,100 Il.2 
The data shown in Tables I and II are graphically represented in 
Figure 2 with some additions at the upper ends of the curves. 
Figure 2 can not be said to represent the rate of increase of velocity 
as a function of depth alone. The velocity of the Pennsylvanian sedi- 
ments shown in Tables I and II, for example, was secured in part 
by measurements of sections of the Pennsylvanian of different age 
in the same wells. Consequently, the increase in velocity with depth 
could be caused partly by the fact that older Pennsylvanian sediments 
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