BORE-HOLE INVESTIGATIONS 



1091 



general very definite. Studies of the foraminifera of the Gulf Coast have 

 contributed widely to an advancement of the geology of that area. In 

 much of the Gulf Coast, however, due to the scarcity of fossils in many of 

 the formations (especially the younger ones) and the non-fossiliferous 

 character of other formations, the number of horizons that can be definitely 

 identified are limited. Identification of paleontological horizons is done by 

 microscopic examination of cores or side wall samples. These samples are 

 obtained by coring or taking side wall samples over that section of the hole 

 in which it is believed the studies should be made. 



Fig. 681. — S.P. placement log in open hole, compared with 

 radioactive marker location and collar log in cased hole. 



Drill Core Measurements. — In the absence of continuous logging data, meas- 

 urements are often made of the magnitudes of certain properties of drill core speci- 

 mens. The magnitudes of the electrical resistivity,t fluid permeability ,$ radioactivity,§ 

 relative mineral content,tt magnetic orientation and permeability,JJ fluorescence, §§ 



t M. W. Pullen, "Tentative Method for Making Resistivity Measurements of Drill Cores and 

 Hard Specimens of Rocks and Ores," U. S. Bureau of Mines, Circular 6141, June, 1929. 



t H. C. Pyle and J. S. Sherborne, "Core Analysis," A.I.M.E. Petroleum Technology, 1939, 

 pp. 33-61. 



§ E. Rothe and T. Kopcewicz, "Comparaison de la radioactivite des roches d' Alsace par 

 la methode des tubes compteurs," Compt. Rend. (1937), Vol. 205, pp. 165-166. 

 tt H. C. Pyle and J. S. Sherborne, toe. cit. 



tt H. N. Herrick, U.S. Patents 1,792,639, issued Feb. 17, 1931; 1,909,619, issued May 16, 

 1933; 2,104,746, issued Jan. 11, 1938. 



H. N. Herrick and E. D. Lynton, U. S. Patent 2,104,752, issued Jan. 11, 1938. 

 §§ J. A. Radley and J. Grant, Fluorescence Analysis in Ultra Violet Light, D. Van Nostrand 

 Co., Inc., New York, 1935. 



