1410 BURTON McCOLLUM AND WILTON W. LoRUE 
territory for very deep domes. The principle of the method used is shown 
in Figure 1. Here, a detector of seismic waves is lowered to the bottom 

Fic. 1.—Diagram illustrating use of well for exploring surrounding region for 
deep donies. Patent applied for. 
of a wildcat well which may have missed the dome. With the detector 
in this position, a series of shots is fired on the surface, on a circle having 
the center approximately at the well and the circumference at a distance 
ranging from 5 to 7 miles from the well. It is obvious that if a dome exists 
anywhere within a radius of several miles of the well, as shown in Figure 
1, the shots from one direction, as S,, will show greater velocity than from 
S, and other directions, thereby indicating the presence and position of 
the dome. If the top of the dome is no more than 2,000 feet below the 
bottom of the well, actual salt occurrences will be recorded on the de- 
tector, thereby giving a very definite lead in the direction of the dome. 
If the dome is much deeper, however, it can be detected because of the 
increased velocity in the shale overlying the dome, as this shale is more 
consolidated and is under abnormally great pressure. In the latter con- 
dition, the increase in velocity, especially if the dome is extremely deep, 
may be small enough so that, in order to make certain of exact shooting 
distances, it may be necessary to determine whether the bottom of the 
hole is directly under its surface location. This can be accomplished by 
the seismograph by shooting four additional shots in four different direc- 
tions approximately a mile from the well, as indicated by S; and S, in 
the section shown in Figure 1. If the bottom of the hole deviates in any 
direction from vertical, this is revealed by the difference in time of arrival 
of the sound wave from the four different directions. By this method 
the direction and amount of drift of the hole can be determined. 
It is obvious that by this method the intervening region between the 
well and the distant shots, particularly that part within 2 or 3 miles of 
the well, can be explored for deep domes to a depth considerably in excess 
of the depth of the well used for the detector. 
Practical experience with this method has demonstrated its useful- 
ness and there is no doubt that the method can be made very eflective 
in exploring the Gulf Coast for domes to a substantially greater depth 
120 
