PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 316th meeting was held at the Cosmos Club, February 28, 1917. 



INFORMAL COMMUNICATIONS 



Frank J. Katz: Age of the Worcester phyllite. (No abstract.) 



REGULAR PROGRAM 



R. V. A. Mills and R. C. Wells: The evaporation of water at depth 

 by natural gases. During the production of petroleum and natural 

 gas in the Appalachian fields the associated waters undergo a definite 

 order of change in the proportions of their dissolved constituents. 

 Along with other gases, carbon dioxide escapes from solution while 

 calcium carbonate and ferrous carbonate are deposited in the wells 

 and in the interstices of the oil and gas bearing rocks. Concentration 

 is brought about bj^ the removal of water as moisture in the escaping 

 gases and at the same time salt is lost from solution. The composition 

 of the salt deposit is approximately: NaCl 94 to 99.5 per cent, MgCl 2 

 2.5 to per cent, CaCl 2 3.0 to per cent, and CaC0 3 0.5 to per cent. 

 The composition of this salt was found by analyses of salt deposits 

 collected from oil and gas wells and gas line pressure regulators; and 

 this composition agrees closely with the composition of the salt deposit 

 that can be predicated from the changes in the composition of the 

 waters during their concentration under known conditions of produc- 

 tion. Some of the pressure regulators, in which gas pressures are 

 reduced from line pressures to distributing pressures, are several miles 

 distant from the wells from which gas is derived. Analyses of salt 

 deposited in the wells and regulators bear a striking resemblance to 

 analyses 'of salt from Louisiana salt domes and salt beds in New York, 

 Michigan, and Kansas. 



Comparisons of analyses of Appalachian oil-field waters from dif- 

 ferent stratigraphic horizons in the same localities indicate that salt 

 of the same general composition has been lost from solution during 

 natural concentration. The investigators are convinced that the 

 evaporative action of natural gas has been an important geologic 

 factor in the changes which many deep-seated waters have undergone. 

 During geologic time enormous volumes of natural gas have passed 



309 



