PRINCIPLES OF OIL ACCUMULATION 253 



monly been made in the laboratory by heating. However, the 

 majority of oil deposits are located in the upper 3,000 feet of sedi- 

 ment, and evidence that the necessary distillation temperature of 

 450° F. has ever been reached at such places is quite lacking. Oil- 

 field waters of this region are seldom above 100° F. in temperature, 

 ranging generally from 80 to 90° F. Consequently it is difficult 

 to explain the reduction of liquid oil from bituminous shales 

 by heat, except possibly in very limited local areas of intense 

 friction. Even in such cases the amount of heat is highly 

 problematical. 



The other most important factor below the surface of the earth 

 is pressure. Pressure alone can cause no change in this material 

 when the included water is not allowed to escape, and the shales 

 are only compacted when the water is given free passage. 



These facts led to a laboratory investigation of rock flowage 

 upon the hypothesis that the mechanical energy or work done 

 upon the shale by applying a force through a distance would 

 accomplish the same results as the equivalent amount of heat 

 energy. The experiment was carried out by Mr. E. A. Trager 

 and the author, similar to the experiments of Adams and 

 Bancroft.^ 



I. Description of flowage experiment. — Cylindrical steel bars (Fig. i) were 

 sawed in lengths of about 3 inches and bored into tubes having an inside 

 diameter of 2 cm. The thickness of the walls in the center of the cylinders 

 was reduced to o. 25 cm. Pistons of steel were turned to fit the tubes. Cylin- 

 drical pieces of an oU shale (yielding 25 gallons per ton and having a crushing 

 strength of about 3,000 pounds per square inch) were cut into i-inch lengths 

 and placed in the center of the tubes, where the thickness of the walls was 

 reduced. The pistons were then inserted on either side of the shale cyhnder 

 and pressure was appUed to them in a Riehle compression machine, thus 

 squeezing the shale and eventually bulging the tubes in the center. By so 

 doing, the shale was made to flow. No appreciable amount of heat was 

 was developed. Solution tests taken before the experiment gave no indication 

 of hquid hydrocarbons, while those taken after flowage with the same shale 

 gave strong coloration. In some cases, after the experiment small globules 

 of oil could be seen in the shale with a hand lens. The steel tubes necessitated 



^ Adams and Bancroft, "On the Amount of Internal Friction Developed in Rocks 

 during Deformation and on the Relative Plasticity of Different Types of Rocks," 

 Jour. Geol., XXV, 597. 



