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Unformatted text preview: t of the hole and a new-similar bit is run to continue the
drilling operations. The pulled bit was graded 1-2-NO-S-IN-NO-PR and some balling at the cutting-structure was observed.
Fig. 12 shows ROP and DSE vs. depth from 2,200 ft to 6,000 ft for field case No. 1. There is steady reduction on ROP
from 125 ft/hr at 2,450 ft to 20 ft/hr at 4,900 ft and then the ROP remains almost constant at 20 ft/hr until the end of the bit
run at 5,300 ft. DSE steadily increased from 14,000 psi at 2,200 ft to 81,000 psi at 3,600 ft. The DSE behavior becomes
increasingly erratic from 3,600 ft to 5,300 ft varying from 50,000 psi to 230,000 psi. At the beginning of the new bit (5,300
ft) the ROP increases to a level similar to the initial ROP for the previous bit (above 100 ft/hr). Then, the ROP steadily
reduces as the drilling continues repeating the behavior of the previous bit. Also, at the beginning of the new bit, DSE
reduces and behaves in a similar way than the previous bit. DSE again progressively increases foll...
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- Spring '13