THEORETICAL DISCUSSION. 
17 
The sand rocks were deposited in the sea, and at that time must 
have been completely saturated. The saline water now contained in 
these rocks may or may not be the water of original deposition. To 
state that the saline water within these sandstones is gradually dimin¬ 
ishing would require proof and many explanations that are not at 
hand. There are, however, facts which point to this condition, the 
most important of which is that the smallest areas of complete sat¬ 
uration are found in the lowest and therefore oldest sandstones, and 
there are certain areas, notably in the Beaver quadrangle, where the 
Berea sand is relatively high and above the line of saturation. 
Within this area very small structural depressions seem to hold accu¬ 
mulations of oil out of proportion to the area drained. 
The upper level of saturation in the Hundred-foot sand is lower 
than in the Berea sand. Oil entering that stratum between F and H 
would accumulate in the syncline at G, with the gas extending to the 
dome at FI and to the limit of the sand toward F. In the synclinal 
trough between H and L the accumulation in the Hundred-foot sand 
would be at the water line above I and above K. 
The area of saturation is less in each sand below the Hundred-foot. 
In the Fifth sand, which is the lowest found within the area so far 
investigated, the accumulation of oil is at the lowest point in the 
syncline, except in the lowest portions of tiny basins along the syn¬ 
clinal trough, where small areas of ponded water still remain. 
PRACTICAL APPLICATION OF PRINCIPLES GOVERNING THE 
ACCUMULATION OF OIL. 
FACTORS INVOLVED. 
The previous discussion shows the importance of a knowledge of 
all the factors governing accumulation in any attempt to locate oil 
territory. These are the porosity of the reservoir rock, the geologic 
structure, and the degree of saturation by water. The first can be de¬ 
termined only by the drill; the second, under favorable conditions, can 
be determined by careful geologic work on the surface, and the third 
by the drilling of a few test wells. Knowledge of the first and third 
factors is absolutely necessary for a correct interpretation of what is 
shown by the map of the surface structure. For instance, in an area 
where two or more sands are productive the map may show produc¬ 
ing wells on the anticlines along the steep slopes and also in the bot¬ 
tom of the synclines, the productive area not appearing in any way 
to conform to the structure; but if the top of the water in each of the 
sands be taken into consideration it will be seen that the sand produc¬ 
ing oil on top of the anticline is wet, the one from which the oil is 
taken in the trough of the syncline is dry, and the one producing 
3496—Bull. 318—07-2 
