"PRINCIPLES OF OIL ACCUMULATION" 369 



McCoy in showing that under common surface temperatures a 

 comparatively vigorous circulation of water will not remove oil 

 from the larger pores of the sand. It does not follow, however, 

 that water circulation could not do this at depths of two or three 

 miles, which does not exceed the probable thickness of strata 

 that formerly covered many oil sands. Further experiments 

 under appropriate higher temperatures are needed to show that 

 gravity alone could not produce anticlinal accumulation in sands 

 buried under a few miles of rock. 



Anticlinal accumulation. — Mr. McCoy appears to believe that 

 the lateral migration of oil in sands is of minor importance. He 

 believes that the anticlinal accumulation, which characterizes 

 most fields, is due primarily to "migration along nearly vertical 

 shale joints, which are most abundant theoretically on the crests 

 and limbs of anticlines. 



There is an asymmetrical distribution of oil in the Cushing and 

 Yale fields, Oklahoma, and in other places where the basin-ward 

 limbs carry the most oil, and carry oil to the lowest structural 

 elevations. This indicates that lateral migration up the slope 

 of sandbeds is an important element in anticlinal accumulation. 

 On the other hand, the frequent distribution of oil in various sands, 

 one above the other, and all above the probable source, as in the 

 Wyoming domes, indicates the importance of joints across the 

 shales. The relation to faults of the principal fields in Kentucky 

 and northern Louisiana bears similar testimony. 



The accumulation of oil in the sand of the Ranger field, which 

 is *'dry" outside of the producing territory, also suggests the in- 

 adequacy of lateral migration in the sands. The occurrence of 

 oil in fractured chert on top of the Santa Maria anticline in Cali- 

 fornia must have been due wholly to migration along nearly 

 vertical crevices, since it would be impossible for oil to move 

 laterally through the hard, dense, unfissured chert on the lower 

 parts of the anticline. Wells drilled on the flanks of this anticline 

 showed neither oil nor water when they passed through the chert 

 horizon. 



In spite of these interesting experiments it seems that the time 

 has not yet come to abandon wholly our previous ideas that an 



