Oil-Field Brines

RECENTLY, Messrs. Mills and Wells1 published a thorough chemical study of the waters associated with oil in parts of the Pennsylvania, Ohio, and West Virginia region. Many of their conclusions are of general application and the writer wishes to discuss some of these: Messrs. Mills and Wells show that the composition of the deep brines of the Appalachian fields is such as would be produced by the evaporation of sea water and the precipitation of sodium chloride, combined with reactions with hydrocarbons and other substances. The brines are altered, also, by considerable mixing with meteoric water. They give good reasons for believing that the concentration of the brines was produced by evaporation in the rock pores induced by migrating gas, much of which probably escaped to the surface of the ground. This hypothesis was considered by the writer in a former paper,2 in which main stress was laid on a second hypothesis, that the excess of chlorine in the deep brines may have been due to the entrance of solutions rich in magnesium and calcium chloride which ascended .from a deep, possibly intratelluric, source. Messrs: Mills and Wells present good arguments for the first hypothesis. Underground evaporation by ascending gases probably will be accepted as the best available explanation of the concentration and composition of deep well waters. They have not considered the possibility that, salt waters in deep sands may be concentrated by the diffusion of water vapor through gas into shale. The writer has given reasons3-for believing that capillary forces concentrate gas and oil in the larger openings of rock, such as the pores of sandstones embedded in shale. The gas underground must be nearly saturated with water vapor at; all times, because it always is in contact with the interstitial water of enclosing shales and of the sand-