BORE-HOLE INVESTIGATIONS 



1085 



small gun is shown in Figure 677.* The gun is fastened to the lower end 

 of a weight or stem suspended by the logging cable. 



Side-wall sample guns in present use contain 6 or 18 bullets and recently a 30-shot 

 gun has been introduced into field use. The 18-shot is the standard gun, and actually 

 consists of three 6-shot guns mounted in one housing. 



r~' "1 



r-st^ 



f I D 



Fig. 677. — Small gun assembly, a, bullet; h, barrel; c, cores; d, body; e, retrieving spring. 

 (Courtesy of Schlumberger Oil Well Surveying Corp.) 



Each bullet in the gun is fired separately at one of the points to be cored. It is 

 thus possible to recover several cores, all from different horizons, within a period of 

 three hours or less, depending on the depth. The gun is lowered into the drill hole on 

 the end of the same cable used to run the electrical log. 



The present guns should not be used in a hole of insufficient diameter to permit 

 the passage of the guns with the bullets fired. The very minimum permissible hole 

 diameter is five inches, and only a 6-shot gun should be used in this case. For the use 

 of an 18-shot gun, it is preferred that the hole be at least seven inches in diameter. 



* A description of a similar gun for taking ocean-bottom samples is given by 

 C. S. Piggot in the "News Science Bulletin," Carnegie Institution of Washington 

 Pub.. Vol. IV, No. 9, Sept. 6, 1936. 



