Miscellaneous Subsurface Methods 



647 



tains the previously discussed merits of providing ample space for the 

 handling of cuttings and ease of cleaning by the mud stream ejected from 

 the water-course nozzles. The mechanical cleaning obtained from inter- 

 fitting the rows of teeth into grooves on mating cones and the twisting- 

 tearing-scraping action of the teeth as they penetrate the formation are 

 fully retained in the OSC-1 tricone. The design differences which do exist 

 are essential for good rock-bit performance in formations slightly hard for 

 the OSC-3 bit. 



Figure 343. Hughes 9-inch type W7R tricone bit. 



The OSC Tricone 



The OSC tricone bit (fig. 341) embodies the same basic principles 

 of design noted in the discussion of OSC-3 and OSC-1 types. The teeth 

 are not so widely spaced or so deeply cut. Although the OSC type is ex- 

 tensively used for drilling unconsolidated shales, redbeds, salt, gypsum, 

 anhydrite, soft lime, etc., it has been used successfully in many oil fields 

 in drilling formations formerly drilled with harder-formation bits such as 

 the OSQ-2 (fig. 344) or OWS (fig. 346) tricone. The footage obtained 

 with the OSC in many instances has been comparable to that obtained with 

 the OSQ-2 or OWS, but the rate of penetration was increased with the 

 OSC design. 



The OSC is more versatile than the OSC-3 in regard to the range of 

 formations which can be drilled. For this reason the OSC is available in 

 a greater range of sizes. 



