VALUE OF WATER ANALYSES TO OIL OPERATOR. 109 
Those who desire to examine oil-field waters for petroleum acids 
may find the following simple test of value. This test, which depends 
on the green color of copper naphthenates, was recently devised by 
Kharitschoff . 1 
The water to be tested is first acidulated with hydrochloric acid and well shaken 
with benzine, which extracts all organic acids, leaving all the sulphur behind. The 
benzine solution is then separated, repeatedly washed with warm water and filtered. 
The filtrate is added with a few cubic centimeters of a solution of copper sulphate and 
three or four drops of piridine or of a strong ammoniac solution, and the mixture is well 
shaken. A green coloration of the benzine on top of the testing tube shows the pres¬ 
ence of petroleum acid in the tested water, and the degree of coloration allows to 
judge of its quantity. 
VALUE OF WATER ANALYSES TO THE OIL OPERATOR. 
Much of the foregoing discussion of the chemical relations of water 
and oil is necessarily hypothetic, owing to the unfortunate lack of 
chemical experimentation bearing on the subject, and although for 
the sake of simplicity only one broad hypothesis has been presented 
it is realized that discussion is by no mean's closed. However, the 
conjectural nature of the conclusions advanced do not affect the 
validity of the main facts presented in this paper, which relate to 
the composition and chemical properties of the oil-field waters them¬ 
selves. There is no question that the normal ground waters are 
very different from those close to or below the oil measures, and that, 
broadly speaking, the horizon at which a water occurs is indicated 
by its chemical composition. According to the few analyses pub¬ 
lished the water associated with the oil in most oil fields is character¬ 
ized by the absence of sulphate, but probably in few regions do these 
waters present such marked contrast with the shallower waters as in 
the San Joaquin Valley, in which sulphate is especially abundant. 
It would seem peculiarly unfortunate therefore if the operators do 
not take advantage of these favorable conditions to use the character 
of the water as a general index of its horizon, for the need for some 
easy means of determining the source of the water flooding a well is 
yearly becoming more pressing. 
The gradations between the strong sulphate waters near the sur¬ 
face and the sulphate-free water near the oil measures have already 
been described. There is little question that in all the San Joaquin 
Valley fields the same order of change from the surface downward is 
to be observed, but the total extent of the change and the point 
above the oil at which it becomes complete are subject to variation. 
In the Westside Coalinga field all the data at hand indicate that the 
alteration of the water is not complete until the oil measures are 
reached, whereas in the Midway and Sunset fields completely altered 
i Kharitschoff, K. V., Petroleum acids in boring waters: Petroleum Rev., vol. 28, p. 380, 1913. 
