OCCURRENCE OF WATER IN OIL FIELDS. 
25 
entered them during 
the Tertiary 
periods of subsidence. 
Further¬ 
more, the stresses incident to the folding of the strata may have 
caused migration from one formation to another; this appears to be 
the most plausible explanation for the local occurrence of salt water 
in the fresh-water beds of late Tertiary age. (See p. 61.) In one 
locality or another salt water is now found in all the Cretaceous and 
older Tertiary formations and in most of the later Tertiary deposits 
as well, but there is usually no way of telling whether or not it is 
connate to the beds in which it occurs, and doubtless much of it was 
entrapped during the most recent periods of immersion. 
GENERAL ASSOCIATION OF SALT WATER AND PETROLEUM. 
It has long been known that in most oil fields petroleum is rather 
closely associated with salt water, and many attempts have been 
made to explain this widespread association. Few analyses of oil¬ 
field waters have been made, however, and the presence of salt in 
many waters has probably been detected by the taste. Although 
presumably the water in most oil fields is salty, and in some is ex¬ 
tremely salty, it may be borne in mind that the degree of saltiness 
is known to be variable and must therefore be influenced to some 
extent by local conditions. 
Presumably on the assumption that all oil-field waters are strongly 
salty Ochsenius, 1 Zaloziecki, 2 Beeby Thompson, 3 and others have 
suggested that the chloride was concerned in the formation of the oil 
itself/ either by acting chemically on the organic matter or by 
retarding premature decomposition. Although there is as yet little 
chemical evidence to support these views it is possible that the 
chloride has exercised some such effect, or has influenced the polymeri¬ 
zation of the oil during a later period in its history. The fact that 
the present distribution of chloride in the oil fields of San Joaquin 
Valley is apparently controlled by local structural conditions would 
not necessarily refute this theory. Such influence as the salt water 
might have would be exercised during the earlier stages of formation 
of the petroleum; and as the diatomaceous shales which are the 
probable source of the California oil are known to have been laid 
down beneath the sea they must have been originally saturated with 
sea water. 
On the other hand, there is a possibility that the occurrence of salt 
water in oil fields may be everywhere explained by the simple prin¬ 
ciples that seem to be effective in the San Joaquin Valley fields, 
namely, that the water is more or less completely trapped in closed 
1 Ochsenius, C., Zur Entstehung des Erdoles: Chem. Zeitung, Band 15, pp. 935 and 1735, 1891; ErdOl- 
bildung: Deutsche geol. Gesell. Zeitschr., Band 48, pp. 239,685, 1896; Erd61 und Salz: Chem. Zeitung,Band 
21, p. 57, 1897. 
2 Zaloziecki, R., Zur Entstehung des Erdoles: Chem. Zeitung, Band 15, p. 1203, 1891. 
3 Thompson, A. B., Petroleum mining, p. 113, 1910. 
