Figure 29-7 shows a bit that has been operated in a balled-up condition. It 

 will be noted that the cones have dragged even though the bearings are in good 

 condition. This type of wear usually occurs in very soft, sticky formations. 

 Balling-up can be the result of (1) the use of excessive weights which causes 

 the teeth to penetrate too deeply into the formation, or (2) the use of insufficient 

 circulating fluid to remove the cuttings. The formation then becomes packed 

 around the cutters and causes them to drag or stick, thus wearing away the teeth 

 exposed to the bottom and sides of the hole. This type of wear can be minimized 

 by (1) decreasing the weight on the bit; (2) increasing the volume or velocity of 

 the drilling fluid; or (3) some combination of these factors. 



Figure 29-8 illustrates a condition, though not common, that can cause a 

 reduction in bit performance in very soft, easily drilled formations. Note the 



Figure 29-8. A bit affected by drilling in soft formations. 



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