COMPOSITION OF THE OIL-FIELD WATERS. 
65 
at a depth of about 3,000 feet its concentration is only 364 parts, 
which is less than that of even the shallowest ground water in most 
localities in the fields of the west side. No oil had been encountered 
at this depth, and if present is probably some distance below. The 
low carbonate-sulphate ratio shown by the analysis indicates a water 
only slightly modified, if at all, though as no shallower water from this 
locality is available for comparison a definite estimate of its relations 
can not be made. No. 33 is a much saltier and more concentrated 
water than any of the foregoing and is included here for purposes of 
comparison. This water has been greatly modified and closely 
approaches the altered water associated with the oil along the western 
edge of the Midway and Sunset fields. (See Table 11, p. 77.) The 
presence of hydrogen sulphide and the appreciable amount of sulphate 
still retained prevent its classification as an altered water, especially 
as it occurs at least a hundred feet above the oil. A similar type is 
shown by analysis 81 (Table 13, p. 83). 
Analysis 80 (Table 12, p. 81) represents a meteoric water of the 
modified type similar in every way to those discussed above but 
formed under very different conditions. This water is the mine water 
at the old coal mine in sec. 26, T. 30 S., R. 14 E. It probably has 
not been affected by oil or gas and its modification must therefore 
be due to the coal. 
60439°—Bull. 653—17-5 
/ 
