OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 53 
COMPOSITION OF THE OIE-FIERD WATERS. 
DESCRIPTION OF THE TYPES. 
GENERAL COMPARISON. 
The analyses of the oil-field waters are discussed and the general 
characteristics of each type are pointed out in the following sections. 
Seventy-three of the analyses given represent the types of water 
found in the Coalinga, Midway, and Sunset oil fields, and these have 
been classified in Tables 1 to 11. In Tables 12 and 13 groups of 
analyses are arranged to show the variation in water from different 
depths. Table 14 contains analyses of types of water from the Kern 
River, Lost Hills, and McKittrick fields, which are introduced to 
show that the same principles apparently govern the character of 
the waters in those localities. Although the classification is directly 
chemical it is indirectly based on the position of the water in rela¬ 
tion to the oil, so that the tables group waters according to their 
horizon as well as according to their composition. A number of 
waters have been included that differ in one particular or another 
from the average for the type, or, if they conform to the type, they 
occupy an apparently anomalous position, and these exceptions are 
explained as far as possible in the discussion. Undue stress has per¬ 
haps been laid on these rarer occurrences, but it has seemed desirable 
to point out at this time such variations from the normal as are most 
likely to be encountered. 
In order to sum up the more important variations in the chemical 
character of the waters and to show graphically their genetic rela¬ 
tions, all the analyses given in this paper have been plotted in figure 4. 
In this diagram the two incompatible properties of waters—sec¬ 
ondary salinity or permanent hardness and primary alkalinity— 
expressed in per cent, represent the horizontal axis to the left and 
right respectively of a common line. All the secondary saline waters 
therefore fall in the left section of the chart and all of the primary 
alkaline in the right. On the vertical axis has been plotted the 
sulphate salinity ratio (per cent of rS0 4 in rS0 4 + rCl), and accord¬ 
ingly all of the sulphate-free waters associated with the oil appear 
along the base line of the chart. The approximate concentration 
(total mineral solids) in parts per million of each water is shown by 
symbols. 
It is believed that the properties selected to represent the axes of 
this diagram furnish the most satisfactory criteria for a broad com¬ 
parison of oil-field waters. It will be noted that most of the surface 
waters, high in sulphate and in alkaline earths, fall in the upper left- 
hand corner of the chart. The normal ground waters of meteoric 
