1412 BURTON McCOLLUM AND WILTON W. LaRUE 
well, shoot a fan of perhaps a 60°-go° angle off the same side of the dome 
as the well. Then another well, as at B, would be used, as shown. On 
this basis, in order to explore the territory entirely surrounding the dome, 
it would be necessary to have five or six wells located at suitable places 
around the dome. It is estimated that by this method a thorough ex- 
ploration of the entire territory within 3 or 3% miles from the flank of 
the known dome can be made down to a depth ranging from 1,000 to 
2,500 feet deeper than the depth of the well used in making the test. 
Such a deep exploration of the area surrounding known domes might 
reveal several deep twin domes. 
DEEP PROFILING OF SALT DOMES 
The problem of profiling deep down the flanks of salt domes has here- 
tofore presented very serious difficulties, and because of these difficulties 
few attempts have been made to profile more than the top of the dome 
and that part extending a very short distance over the shoulder. The 
recent successful use of the described method of placing detectors in 
wells and exploring the surrounding country for deep domes has opened 
the way for the development of an accurate method of profiling down the 
sides of salt domes to depths ranging from 5,000 to 6,000 feet. A method 
for accomplishing this purpose has always been considered extremely 
desirable, but it has recently become of vastly greater importance with 
the discovery of the mushrooming tendency on some salt domes in the 
Gulf Coast region. 
The general method of procedure is simple, as shown by an inspection 
of Figure 3. Here a shot is placed as shown at some convenient point 
on the opposite side of the dome from the well which is being used in the 
exploration; a detector is let down in the well to any suitable position 
such as D,, and a shot made. The detector is then lowered in the well to 
the point D,, and so on, shots being made with the detector spaced at 
suitable intervals down to the bottom of the well. It is readily under- 
stood that the total time of travel of the shot to different detector posi- 
tions is a function of the spacing between the well and the salt mass. 
With a knowledge of the velocity of sound in rock salt and its velocity 
in the deep shales, together with the geometrical relationships involved, 
it is possible to calculate the form of the profile of the dome opposite the 
well with considerable accuracy. In this way it can be determined with 
certainty whether or not the dome slopes continually outward or whether 
it recedes with increasing depth, as shown in Figure 3. 
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