80 
OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
The carbonate line rises from 2 per cent in the first- water to 32 per 
cent in the third, and then, owing to the great increase of chloride in 
the bottom water, decreases to 18 per cent, although if the actual 
amount were plotted it would continue to increase. (See analyses 
74-77, Table 12.) Chloride increases only slightly down to the third 
water, but in the lowest shows a marked rise. The alkalies increase 
regularly with depth and the alkaline earths decrease. The con¬ 
centration shows a slight rise in the second water, a fall in the third, 
and a marked rise in the fourth. The lower concentration of the third 
water is presumably due to the formation of the relatively insoluble 
carbonates of the alkaline earths, which are precipitated. This also 
explains the loss of alkaline earths and the rise of alkalies in the third 
water; if actual amounts were plotted instead of percentages the 
earths would fall off even more abruptly, whereas the alkalies would 
show little increase. To sum up these variations, alkalies, chloride, 
carbonate, and the concentration value increase with depth, whereas 
alkaline earths and sulphate decrease. The most marked variations 
are exhibited by sulphate and carbonate, and although it happens 
that in this locality chloride also increases greatly in the water be¬ 
neath the oil, it may easily be shown by comparison with other areas 
that the rise in chloride is a local feature, and has no special sig¬ 
nificance. 
Analyses 78 and 79, Table 12, represent waters encountered at 
370 and 3,700 feet, respectively, in a well drilled for oil several miles 
north of the Eastside Coalinga field. No oil had been encountered 
when the lower water was reached, and it is believed that both waters 
are unaffected by hydrocarbons. These analyses may therefore be 
considered as showing the normal changes that take place with in¬ 
creasing depth. It will be noted that No. 78 is a secondary saline 
water, and that No. 79 is slightly primary alkaline owing to an 
increase in alkalies without a corresponding increase in strong acids. 
The sulphate salinity ratio in No. 78 is 80 per cent and in No. 79, 76 
per cent, and the carbonate-sulphate ratios are, respectively, 0.16 
and 0.13. 
