100 OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
PRODUCTION OF GASES. 
Whatever the reactions controlling the character of the oil-field 
waters may be, it is clear that sulphide, free hydrogen sulphide, 
carbonate, bicarbonate, and free carbon dioxide are formed. The 
particular significance of the gases hydrogen sulphide and carbon 
dioxide will be briefly considered. 
Although the sulphide radicle is probably first formed during the 
reduction of sulphate, it is ordinarily so unstable that hydrogen 
sulphide may be considered the final product. As this gas is found 
in many of the waters above the oil measures, and as these waters 
still contain some sulphate, it is probable that they are undergoing 
alteration at the present time. The strong odor of hydrogen sulphide 
may readily cause overestimation of the amount present in a water. 
The greatest amounts that have come to the writer’s attention, which 
are reported in waters from the Eastside Coalinga field, do not exceed 
350 parts per million, and few waters carry more than 50 parts. As 
the complete reduction of 10 parts of sulphate would yield 3.5 parts 
of hydrogen sulphide, it is evident that either the sulphate in the 
upper waters is not all reduced directly to hydrogen sulphide or else the 
hydrogen sulphide is being removed from the solution nearly as 
rapidly as it is being formed. Some of it may unite with iron to 
form iron sulphide, which is precipitated. A small amount of hydrogen 
sulpiride has been found in some of the hydrocarbon gas, but the total 
quantity accounted for in this way is not great. 
As hydrogen sulphide readily oxidizes to sulphur, even under 
very feebly oxidizing conditions, considerable amounts of it are 
doubtless oxidized to sulphur and so removed by precipitation from 
the waters above the oil measures. 1 As the strata above the oil 
measures have not been examined for sulphur this hypothesis can 
not be definitely proved, but commercial deposits of sulphur have 
been found near the south end of the Sunset field, in sec. 21, T. 11 
N., It. 23 W., in pockets and fissures in the McKittrick formation, 
which includes the oil measures in the producing field near by. 
Most of the sulphur is amorphous, but some of it occurs as clear 
yellow crystals as much as a quarter of an inch in diameter. A 
steady flow of hydrogen sulphide is emitted from a pipe which has 
been driven a short distance into the ground near one of the prospect 
pits. A very interesting feature of this sulphur is its intimate mix¬ 
ture with hydrocarbon material, which seems to constitute 20 per 
cent or more of the amorphous substance. No oil or tar seeps are 
found in the immediate neighborhood of the sulphur deposits, but 
deposits of brea occur less than a mile away. Small deposits of 
1 The precipitation of sulphur by the oxidation of hydrogen sulphide is discussed in detail by Walter 
F. Hunt (Origin of the sulphur deposits of Sicily: Econ. Geology, vol. 10, pp. 543-579, 1915). 
