Figure 1. Schematic of the underreamer tool. 

Figure 2. Photo of bi-center reamer.

Figure 3. Expanded underreamer below conductor casing. 

Figure 4. Underreaming in unstable sediment.

Figure 5. Bi-center reamer.

Figure 6. Mud motor with bi-center reamer and pilot bit. 

Table 1. Closing and drill bit specfications.

Table 2. HOC specifications.

Table 3. DDI specifications.