PRINCIPLES OF OIL ACCUMULATION 255 



contact with the oil-soaked shale. Oil shales are usually sepa- 

 rated from sand or porous rock by barren shales. These over- 

 lying and underlying a water stratum would be saturated with 

 capillary water, and it would be impossible for oil to migrate 

 through even a very thin water shale, for reasons stated later. 

 It then becomes necessary for breaks in the intervening shale 

 to occur so that the water may come in direct contact with the 

 oil-soaked horizon. Such conditions can be brought about only 

 by faulting or jointing. A very small displacement or a slight 

 open joint may give the water from large openings a chance to 



Fig. 2. — Diagram of apparatus for accumulation experiment before partition' was 

 removed, showing oil in shale marked "D." 



enter the oil-soaked shale and the oil to exchange places with the 

 water. To substantially back these statements, the following 

 experiment is offered : 



2. Description of accumulation experiment. — A water-soaked sand bed {B) 

 two inches thick was placed in a glass box 18 in. by 6 in. by 6 in. (Fig. 2). In 

 the center of the box a celluloid sheet partition was set at a slight angle to the 

 vertical and effectively sealed to the sides and bottom of the box with putty. 

 Each division of the box was then water-tight. The sand bed was buUt 

 higher on one side of the partition than on the other; the beds on each side 

 of the partition were slightly sloping in the same direction, representing a 

 normal fault. About one inch below the top of the sand bed was a thin layer 

 of coarser sand {A) running uniformly throughout. Water-soaked mud (C) 

 from ground shale (passing a 200-mesh sieve) was placed above the sand. 

 This layer was about one inch thick. Then a one-inch layer of oil-soaked 

 mud (J9) was built over the area adjoining the ceUuloid partition, but not 

 extending to the corners of the box. The reason for not covering the entire 

 area with oil-soaked shale was to avoid the fittings around the corners as a 

 perfect seal is hard to accomplish in corners of such a small box. The 



