. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. INTERPRETING RESULTS ON DEPTH CALCULATION 45 both considered and are plotted on the profile. The sharp break with large amplitude is the first impulse on records 2B and 2B', while on the longest three records the sharp break is preceded by an absorbed impulse which is characteristic of the igneous basement. Several other profiles in the same general area as profile B all had a small wave of short period on the second horizon which required large dynamite charges to bring out. A curve drawn through t
. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. INTERPRETING RESULTS ON DEPTH CALCULATION 45 both considered and are plotted on the profile. The sharp break with large amplitude is the first impulse on records 2B and 2B', while on the longest three records the sharp break is preceded by an absorbed impulse which is characteristic of the igneous basement. Several other profiles in the same general area as profile B all had a small wave of short period on the second horizon which required large dynamite charges to bring out. A curve drawn through the points represented by the first small impulse or "forerunner" does not intersect the curve drawn through the points representing the sharp breaks of the third horizon until after the basement velocity curve intersects both of them. Should the small wave or "forerunner" bs interpreted as a thin lens-like formation overlying the horizon -which gives the sharp break, or is it a separate acoustic horizon? If the former, it might be dis- regarded as far as depth calculation is concerned, but if it is the latter its thickness must be considered. THEORETICAL CONSIDERATION If the conditions shown in Figure 1 be assumed, it is possible to derive equations for the time-distance curves which these velocities s. Fig. i.—Assumed conditions of depth and velocity. 375. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Society of Exploration Geophysicists. Tulsa
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