Roller cone bit

Figure 4-138. Roller cone bit design trends [44]. (Courtesy SPE.)...

Dull Grading of Roller Cone Bits. The grading is accomplished by using an eight-column dull code as follows [46]. 

Column 4 (L) uses a letter or number code to indicate the location on the face of the bit where the major cutting structure dulling characteristic occurs. Table 4-93 lists the codes to be used for describing locations on roller cone bits. 

Bit Wear and Rock Type. Using downhole weight-on-bit and torque the roller cone bit wear can be estimated while drilling. The well site computer can be used to compute in real-time a dimensionless torque (T ) and a dimensionless rate of penetration (R ) using the following equation ... 

The most frequently used bit types are the roller cone or rock bit (F g. 3.8) and the polycrystalline diamond cutter or PDC bit. 

The elements of the roller rock bit are shown in Figure 4-137 [45]. Roller rock bits have three major components the cone cutter, the bearings and the bit body. The cutting elements are circumferential rows of teeth extending from... 

A roller rock bit is pulled out of the hole after 12 hr of rotation at the bottom. The driller estimates that the worst cone could rotate 4 hr more before being completely worn out thus total bearing life estimated is 16 hr. 

Figure 4-139. Roller bit cone design features. (Courtesy Canadian Association of Oilwell Drilling Contractors.)...

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