Many reports of formation water analyses show determinations only for carbonate, bicarbonate, sulfate, chloride, calcium, magnesium, and sodium ions. Waters from various geological formations are classified by the systems of Palmer, Sulin, and Schoeller. These systems are compared and it is concluded that Sulin's system is more descriptive of petroleum formation waters than are the other systems.

According to Sulin's system, waters known to be in contact with petroleum are of the following types: chloride-calcium > bicarbonate-sodium > chloride-magnesium >>> sulfate-sodium. In Schoeller's system, positive indications of base exchange are calculated for Sulin's chloride-calcium and chloride-magnesium types with negative indications for bicarbonate-sodium and sulfate-sodium types. Sulin's system shows changes in water type as infiltrated water moved downdip in "Trenton" and Woodbine formation waters.