I 
OCCURRENCE OF WATER IN OIL FIELDS. 29 
enough to be potable, whereas in others it is nearly as salty as sea 
water. Many of the deeper top waters are confined under high 
pressure and flow at the surface. In most localities there is a rising 
or flowing water a short distance below the top oil sand, and in the 
deeper part of the syncline this oil sand is itself water bearing. 
Where second and third oil sands have been found, strong water 
sands are generally present between them. Although the water 
pressure as a rule is high, it is decidedly variable, and “dry” sands 
have been reported in many places. The deeper waters in this part 
of the field are fairly uniform in chemical character but differ from 
those at the same horizon in the shallower western part of the field. 
(See figs. 6, p. 88, and 7, p. 91.) Their average temperature is also 
different, being ordinarily some 10° higher. 
KERN RIVER FIELD. 
The Kern River field, lying on the lowest foothills of the Sierra 
Nevada on the east side of San Joaquin Valley, differs in many 
respects from those just described. The geologic structure is rela¬ 
tively simple; the strata lie in a gentle monocline, which is modified 
in places by minor wrinkles. The oil sands are very thick and are 
highly productive, but the gas pressure has never been very high. 
Kern River, which has a large drainage basin in the Sierra Nevada 
flows along the edge of the field. The waters draining from the Sierra 
are very different in chemical character from the waters on the west 
side of the valley and contain only a very small amount of dissolved 
salts, which are chiefly carbonates. The ground-water level in the 
Kern River field is high, and in most localities abundant supplies of 
potable water are obtained relatively close to the surface, and thence 
at short intervals down to a depth of many hundred feet. In general 
the percentage of dissolved salts increases with depth, but even in 
the deepest waters reached is usually less than in the average shal¬ 
low water in the fields of the west side. Owing to the sandy char¬ 
acter of the strata and to the fact that no pronounced structural 
barrier separates the field from the valley proper, the underground 
circulation is less restricted than in most of the fields of the west 
side, and the general water pressure is therefore comparatively low. 
Flowing waters have been encountered, but they are not common. 
ANALYSIS OF WATER AND INTERPRETATION OF 
RESULTS. 
MINERAL CONSTITUENTS IN WATER. 
Natural waters are essentially solutions of mineral substances 
which have been derived from the rocks or other material with which 
the waters have come in contact. All solutions may be regarded as 
homogeneous bodies, through which the mineral substances are 
