96 OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
Black Sea contains 6,550 parts per million of hydrogen sulphide, 
and Zelinsky 1 has identified in the bottom muds of the Black Sea 
several species of anaerobic bacteria that are very active in the 
formation of hydrogen sulphide. Murray and Irvine 2 report the 
formation of unstable sulphide in sea water associated with the blue 
muds on the floor of the ocean and by a series of analyses show that 
some of the sea water drained from the muds contains only 50 per 
cent as much sulphate as normal sea water. They note a con¬ 
comitant increase in the alkalinity of the water, due principally to 
the formation of carbonate, and a slight loss of lime, due to the 
precipitation of calcium carbonate. This implies a decrease in 
secondary salinity and an increase in secondary alkalinity, limited 
by the solubility of the calcium carbonate; or, in other words, an 
approach to the oil-field brines along the lines explained above. 
It is therefore well established that sulphate may be reduced by 
bacteria in the presence of organic matter, but the bearing of this 
process on the development of the composition of oil-field waters 
is conjectural. It may be assumed, if desired, that the connate 
water was completely altered by the action of bacteria shortly after 
being entrapped in the sediments, as suggested by the observations 
of Murray and Irvine, but the alteration of the meteoric water is 
more difficult to explain. There is no evidence to show that even 
anaerobic bacteria can continue to exist in the muds after they 
have been covered with a thousand feet or more of other sediments 
and elevated into land, and certainly some time must have elapsed 
after the elevation before meteoric water penetrated to the zone of 
alteration. In fact, the writer is inclined to believe that in some 
localities meteoric waters are percolating down to this zone and are 
being reduced at the present time. Hence, unless it be assumed that 
bacteria are present in the strata to depths of several thousand feet 
the formation of the sulphate-free waters can not be ascribed to 
bacterial action, except perhaps in part. 
The belief that hydrocarbons can reduce sulphate at moderate tem¬ 
peratures in the absence of bacteria has been tacitly accepted for 
many years, and few attempts have been made to prove it in the 
laboratory. In the anhydrous condition gypsum (CaS0 4 ) is a very 
stable compound, and it has been found that a temperature of 
about 700° C. is required for its reduction, even with a fairly active 
reducing agent, such as carbon monoxide. 3 In solution, however, 
1 Zelinsky, N. [Sulphydric fermentation in the Black Sea]: Russ. Chem. Soc. Jour., vol. 25, pp. 298-303, 
1894; abstract in Chem. Soc. Jour., vol. 66, pt. 2, p. 200, 1894. Andrussow, N., Physical exploration in 
the Black Sea: Roy. Geog. Soc. Geog. Jour., vol. 1, p. 49, 1893. 
2 Murray, John, and Irvine, Robert, On the chemical changes which take place in the composition of 
sea water associated with blue muds on the floor of the ocean: Roy. Soc. Edinburgh Trans., vol. 37, p. 
481, 1892-93. 
3 IJofman, II. O., and Mostowitsch, W., The reduction of calcium sulphate by carbon monoxide and 
carbon, and the oxidation of calcium sulphide: Am. Inst. Min. Eng. Bull., pp. 913-939, 1910. 
