586 abstracts: geology 



Frequency differences of doublets in the spectra of sodium, potassium, 

 rubidium, caesium, and copper are shown to be constant in most cases 

 to one part in 100,000 in the number of waves per centimeter. 



W. F. M. 



GEOLOGY. — Chemical relations of the oil-field waters in San Joaquin 

 Valley, California. G. Sherburne Rogers. U. S. Geological 

 Survey Bulletin 653. Pp. 119. 1917. 

 The chief conclusions concerning the chemistry of the waters, de- 

 duced from a study of several hundred analyses of water from different 

 depths, are as follows: 



1. Oil-field water is not necessarily salty, as is generally believed, 

 and may not be even slightly salty to the taste. The degree of con- 

 centration of chloride in such water is governed primarily by local 

 conditions and is not affected by the position of the water in relation 

 to oil. 



2. Sulphate, which predominates in most of the shallow ground 

 waters on the west side of San Joaquin Valley, diminishes in amount 

 as the oil zone is approached and finally disappears. 



3. The concentration of carbonate increases as the oil zone is 

 approached but depends largely on the concentration of chloride. 



4. The horizon, with respect to the oil zone, at which these altera- 

 tions take place, is different in each field. 



On the basis of these conclusions, which appear to be well grounded, 

 at least for the area studied, the following practical suggestions may 

 be made: 



In drilling a well in untested territory it may be possible to obtain 

 an indication of the presence or absence of oil and gas below by ascer- 

 taining by analysis whether the sulphate is diminishing and the car- 

 bonate increasing in the waters successively encountered. In some 

 areas a significant change may be detected as much as 1,000 feet above 

 the oil; in others the upper limit of alteration may be within a few 

 hundred feet of the oil. 



The source of the water in a well that produces a mixture of water 

 and oil may be determined, at least in a general way, by studying its 

 chemical composition. In the Westside Coalinga field, for example, 

 the source of the water may thus be determined rather definitely; in 

 the Midway-Sunset field, where the distinctions are less sharp, the 

 success of this method will depend largely on the number of authentic 

 analyses that are available for comparison. G. S. R. 



