COMPOSITION OF THE OIL-FIELD WATERS. 
71 
Brine .—In Tables 8 and 9 are shown analyses of brine, or connate 
water, altered presumably by the action of hydrocarbons. For 
convenience in discussion the term brine is here restricted to waters 
that are practically sulphate-free and that are characterized by 
secondary salinity. The primary salinity generally ranges upward 
from about 80 per cent and the secondary salinity downward from 
about 20 per cent; the concentration is generally between 25,000 and 
45,000 parts per million, and secondary alkalinity is therefore very 
low. The greatest actual amount of sulphate in any of the waters 
shown is 34 parts per million, and owing to the large amounts of 
chloride present the sulphate salinity ratio is less than 0.5 per cent. 
Owing to the very small amount of both carbonate and sulphate the 
ratio between them generally has little significance. To facilitate 
comparison an analysis of ocean water is included in Table 8 as No. 52. 
Analysis 46 represents a very exceptional water from the Coalinga 
field, which is exactly on the dividing line and exhibits neither 
secondary salinity nor primary alkalinity. Carbonate is low and 
only a trace of sulphate is reported, so that this water is essentially 
a solution of sodium chloride. The concentration is unusually low 
and secondary alkalinity is present in corresponding high proportion. 
A partial analysis of a deeper water from the same well showed more 
chloride and less carbonate, indicating a true (secondary saline) 
brine. Both these waters are said to be from the brown shale below 
the oil measures. Apparently no brines have been encountered in 
the main Coalinga field south of this well, though they probably 
exist in the deeper unexplored portion of the syncline. 
The remaining analyses in Table 8 represent brines from the 
Midway syncline and the Buena Vista anticline. All these waters 
occur close to the oil, some a short distance above and others below. 
In all of them the sulphate salinity ratio is less than 0.1 per cent and 
two of them contain no sulphate whatsoever. In all other respects 
they closely resemble sea water, the properties of reaction varying 
within the limits stated above and the concentration ranging between 
29,000 and 39,000 parts. No. 48 is the only oil-field water that has 
come to the writer’s attention in which secondary salinity is as high 
as it is in sea water. 
Table 9 contains analyses of seven brines from the Midway and 
Sunset fields. Nos. 53 and 55 to 58 are in every way similar to those 
already described and are believed to be representative of the water 
associated with the oil in the central and eastern parts of these fields. 
Nos. 54 and 59 are somewhat different types, having a very much 
lower concentration than the rest. No. 54 contains an exceptionally 
high proportion of the calcium and carbonate radicles and primary 
and secondary salinity are therefore unusually low. No. 59, which is 
t 
