Effect of Dissolved Gas upon the Viscosity and Surface Tension of Crude Oil

Abstract

In the course of the experimental and development work of Henry L. Dohertyin an endeavor to obtain an increased yield of oil from oil-bearing sands, itwas Mr. Doherty's claim and contention that oil in an undisturbed pool wasdifferent in character and behavior than the same oil when raised to thesurface of the earth, and that the gas dissolved in the oil caused a markedreduction in its viscosity and surface tension. Prior to 1924 no information tosupport this contention could be found in the literature or by a discussion ofthe subject with technical men in Government and private laboratories. So faras could be ascertained no experimental work had been carried on to indicatethat Mr. Doherty's claim was either right or wrong. All parties consultedagreed that the viscosity of the oil would be affected by gas dissolved thereinto the extent that natural gasoline was present in the gas, but so far as couldbe determined any additional effect of the natural gas was unknown. Accordingly, it was necessary to devise equipment and carry on experimentswhich would either prove or disprove Mr. Doherty's contention or claim. Suchapparatus was built under Mr. Doherty's direction and experiments were carriedon to determine definitely the viscosity and the surface tension of the crudeoils which contain dissolved gases under different pressures. The results ofthe experimental work carried on have proved that the claim and contention ofMr. Doherty were correct in every particular, as will be seen from thediscussion of the subject and the data contained in this paper. Reduction of Viscosity by Dissolved Gas At a pressure of 500 lb., and a temperature of 70?F., it was found that anatural gas such as is associated with the oil would reduce the viscosity about50 per cent when a given crude oil was saturated with the gas. Increasing thepressure another 500 lb. could not be expected to reduce the viscosity theremaining 50 per cent. However, some reduction in viscosity would take place asindicated by the curves showing the relation between pressure and relativeviscosity.