ABSTRACT
In general, waters in Wyoming oil fields show a tendency toward a reduction in sulphate content and increase in carbonate and chlorine content and general concentration with increasing depths unless the waters have been modified by circulation. Secondary salinity decreases with depth, and in cases of deeper sands disappears altogether.
The Dakota sand waters show a content of sulphate at greater depths than the Frontier sand waters, due to more rapid water circulation and general replenishment of sulphates to the deeper waters.
In Wyoming fields, waters in contact with oils show a tendency toward the reduction of sulphates and increase in carbonates. Oils in contact with underground waters are altered and show a reduction in lighter fractions which results in lower-gravity oil. The Salt Creek field shows alteration of the oil in a zone extending from 100 to 150 feet above the water line. In the Big Muddy field, the oil appears to be altered over the entire producing area, probably due to rapid water circulation which is shown by the high sulphate content of the water, tilted water table, and nearness of outcrops.
