A 40 degrees A.P.I. crude shale oil has been produced from the Green River Formation in the Piceance Creek Basin of Colorado by injection of hot natural gas at a controlled temperature. The quality of the shale oil differs very markedly from the customary shale oil from the same formation produced in a high temperature retort. The characteristics of the oil fractions have now been determined. These include distillation analyses, viscosity, and pour point determination.
Kinetic data on the production of the shale oil under the conditions used in the field, but carried out on a small scale in the laboratory will be presented. A possible mechanism for the production of this oil, as well as a mechanism for the production of shale oil by more usual high temperature methods will be presented.
Various methods for the production of shale oil by in situ techniques are being investigated in the United States. The method with which this paper is concerned involves the use of hot natural gas as the energy conveying medium to convert the kerogen in the oil shale to a petroleum like liquid. The basic concept, which was developed by the late J.L. Dougan of Equity Oil Company and tested in the Fuels Engineering Department laboratories at the University of Utah and subsequently field tested in the Piceance Creek Basin of Colorado, is basically a low temperature conversion and distillation process. Natural gas is heated to a temperature below its thermal decomposition temperature and injected through an insulated pipe into the Green River Oil Shale formation where it loses its heat rapidly to the oil shale, gradually raising the temperature of the shale toward that of the injected gas. The kerogen is converted to bitumen and finally to a low pour point, high gravity crude oil.
Since the temperature of the natural gas is below that for thermal decomposition of the mineral carbonates in the oil shale, little CO2 is produced. The natural gas is compatible with the oil, being soluble in it; this aids in the penetration of the formation by the natural gas and in the heat transfer. Since the heating gas is completely free from oxygen, no oxidation induced polymerization of the oil occurs.
Prior to the field experiment, oil shale cores from the Piceance Creek Basin were heated in a natural gas stream under two conditions. Some experiments were run at a gas pressure of 300 lb/sq. inch.