58 
OIL-FIELD WATERS 11ST SAN JOAQUIN VALLEY, CAL. 
NORMAL GROUND WATER. 
Shallow water wells —Analyses of normal ground water from shallow 
water wells in the Coalinga, Midway, and Sunset fields are given in 
Table 2. These waters, like the surface waters, show a rather wide 
range in composition. All of them except Nos. 9 and 14 are secondary 
saline waters, but the secondary salinity is generally lower than in 
the surface waters and the primary salinity higher. Chloride and 
the alkalies are somewhat higher, especially in the waters from the 
Midway field. 
Analyses 8 and 9 represent shallow well waters from the Eastside 
Coalinga field. They are very similar in composition, though on 
opposite sides of the dividing line, No. 8 being slightly secondary 
saline and No. 9 showing 1.8 per cent of primary alkalinity. Analysis 
10 shows the general composition of the water in many of the shallow 
wells in the northern part of the Westside Coalinga field. Nos. 11 
and 12 are very similar to surface waters, although in No. 12 chloride 
is high. Analyses 13 and 14 represent waters from the Midway-Sun¬ 
set field, both of which are characterized by high chloride. No. 14 
represents a mixed water derived from two sands, 450 feet apart, the 
deeper of which has probably contributed the small percentage of 
primary alkalinity present. 
Analyses 84 and 87 (Table 14, p. 85) represent shallow ground 
, waters of very different types from the Kern River and Lost Hills 
fields. No. 84 is similar to the water of Kern River, already dis¬ 
cussed, differing from it only as the shallow ground waters of the 
west side of the valley differ from the surface waters of that region. 
No. 87 is water from a well 180 feet deep, located somewhat west of 
the axis of the Lost Hills anticline. Its properties are very close to 
those of sea water (see fig. 4, p. 54), the chief differences being a 
slight reduction in sulphate and a very small increase in carbonate. 
The concentration is exceptionally high for a shallow water, being 
over a third of that of sea water. This water is distinctly a connate 
type, and the slight alteration that it has undergone is remarkable 
in view of its proximity to the surface. 
Oil wells (top water ).—Tables 3 and 4 contain twelve ana.yses of 
normal ground water or top water from oil wells in the Coalinga and 
Midway-Sunset fields. There is, of course, no essential difference 
between these waters and those from shallow water wells, the sepa¬ 
ration being merely one of convenience. However, most of these 
waters are deeper than those shown in Table 2, and consequently 
the primary salinity is generally higher and the secondary salinity 
and secondary alkalinity lower. The concentration is generally 
higher, and in several waters is very high. 
