8 
OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
mine whether or not this zone of altered water may be satis! actorily 
subdivided. Even if this differentiation could not be made analyses 
will be of great value in locally correlating the various waters, as, for 
example, in determining whether or not the water produced by two 
neighboring wells is the same. 
It is generally recognized to-day that the problem of preventing 
water from invading the oil sands is one of the gravest problems con¬ 
fronting the oil industry in California. By following the methods sug¬ 
gested in this report a clue can probably be obtained to the source of 
the water that floods a well, a knowledge of which is essential to its 
proper exclusion. These methods are being successfully used by the 
Standard Oil Co. and should prove equally valuable to other 
operators. 
It may be oorne m mind, however, that the work of gathering the 
data must fall on the operators themselves, for it is impossible for 
anyone not constantly on the ground to collect an adequate set of 
samples. An analysis is of little value as a standard for comparison 
unless the position of the water is known, and properly located sam¬ 
ples can usually be taken only while the well is being drilled or 
repaired. The samples need not necessarily be analyzed immediately 
but may be sealed and stored away until their analysis becomes 
desirable. Several of the larger companies have begun to realize 
the value of analyses and are taking samples wherever good ones can 
be obtained. It is well to bear in mind that the trouble and cost of 
collecting a sample and having it analyzed are negligible in compari¬ 
son with the value that the information thus made available may 
later acquire. 
LOCATION OF THE OIL. FIELDS. 
The oil fields of San Joaquin Valley are in Fresno and Kern coun¬ 
ties. The most important fields are on the west side of the valley, 
along the flanks of the Coast Ranges, and extend, with intervening 
unproductive areas, for a distance of 110 miles. The Coalinga field, 
in Fresno County, is the northernmost of the developed fields, and the 
Midway-Sunset field, in Kern County, is the southernmost. The 
Lost Hills and Devils Den districts are roughly halfway between the 
two, and the Belridge and McKittrick fields are between the Devils 
Den and the Midway. The only field on the east side of San Joaquin 
Valley is the Kern River field, which is on the lowest foothills of the 
Sierra Nevada near Bakersfield, about 30 miles northeast of the 
Midway-Sunset field. By far the most important of these fields, 
named in order of age of exploitation, are the Kern River, Coalinga, 
and Midway-Sunset fields. At present, however, the Midway-Sunset 
field is the largest in the State in annual production, and it is followed 
by the Coalinga and the Kern River, in the order named. 
