COMPOSITION OF THE OIL-FIELD WATERS. 
75 
Mixed type .—In Tables 10 and 11 are shown analyses of waters of 
mixed meteoric and connate origin, altered presumably by the action 
of hydrocarbons. This type naturally overlaps on the two preceding, 
for few waters can be considered wholly meteoric or wholly connate, 
but it appears to have a fairly definite geographic distribution. (See 
p. 88.) The type may be defined as comprising primary alkaline 
waters that are characterized by less than 50 per cent of primary 
alkalinity and that contain practically no sulphate. Primary salinity 
usually ranges between 55 and 85 per cent and secondary alkalinity 
between 1 and 10 per cent. The concentration is intermediate 
between that of the reversed type and that of the brine, but generally 
ranges between 6,000 and 12,000 parts. (See fig. 4.) 
Table 10 includes five analyses of this type of water from the West- 
side Coalinga field. In this locality the mixed type everywhere 
occurs in or below the oil measures and constitutes the bottom water, 
but so far as is known it does not occur above them. The only excep¬ 
tion to this statement is found in the water which in the deeper por¬ 
tion of the field replaces the oil in the highest oil sand, the so-called 
“upper edge water.” This is represented by analysis 62 and the 
bottom water by analyses 60, 61, 63, and 64. Two of these waters 
contain no sulphate whatever, in two others it is negligible, and in 
the other it amounts to 37 parts per million. The primary alkalinity 
ranges between 23 and 42 per cent and the other properties vary 
accordingly. The concentration ranges between 4,000 and 8,000 
parts. 
Analyses 65 to 73, Tables 10 and 11, represent waters of the mixed 
type in the Midway and Sunset fields. Generally speaking, these 
waters exhibit lower primary alkalinity and higher concentration 
than the Coalinga types; in other words, the mixture contains a 
somewhat larger proportion of connate water. In the Midway and 
Sunset fields this type of water is found both below and above the 
oil, No. 70, for example, occurring 700 feet above the main oil zone. 
The type is confined to the western edge of the fields or to the zone 
nearest the outcrop. 
In No. 73 the sulphate amounts to 27 parts per million; in the 
remainder it is either absent entirely or present in negligible amount. 
The properties of reaction and the concentration show essential regu¬ 
larity within the limits defined, although Nos. 66 and 72 show lower 
primary alkalinity and higher concentration, indicating a larger pro¬ 
portion of connate water. Analysis 82 (p. 83) shows another example 
of this type from the Midway field. 
Analysis 86 (Table 14, p. 85), represents a water of the mixed type 
encountered near the bottom of a well 5,135 feet deep in the Kern River 
field. It is similar in every way to the waters of this type from the 
fields on the west side of the valley, except that its concentration is 
