STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Drilling Bits and Downhole Tools 781
4. 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 he used for describing locations on
roller cone bits.
5. Column 5 (B) uses a letter or a number code, depending on bearing type,
to indicate bearing condition on roller cone bits. For nonsealed bearing
roller cone bits a linear scale from 0 to -8 is used to indicate the amount
of bearing life that has been used. A 0 indicates that no bearing life has
been used (a new bearing), and an 8 indicates that all of the bearing life
has been used (locked or lost). For sealed bearing (journal or roller) hits
a letter code is used to indicate the condition of the seal. An “E” indicates
an effective seal, and an “F” indicates a failed seal(s).
6. Column 6 (G) is used to report on the gage of the bit. The letter “I”
indicates no gage reduction. If the bit does have a reduction in gauge it
is to be recorded in + of an inch. The “two-thirds rule” is correct for threecone
bits. The two-thirds rule, as used for three-cone hits, requires that
the gauge ring be pulled so that it contacts two of the cones at their
outermost points. Then the distance between the outermost point of the
third cone and the gage ring is multiplied by two-thirds and rounded to
the nearest & of an inch to give the correct diameter reduction.
7. Column 7 (0) is used to report any dulling characteristic of the bit, in
addition to the major cutting structure dulling characteristic listed in
column 3 (D). Note that this column is not restricted to only cutting
structure dulling characteristics. Table 1 lists the two-letter codes to be used
in this column.
8. Column 8 (R) is used to report the reason for pulling the bit out of the
hole. Table 4-94 lists the two-letter or three-letter codes to be used in this
column.
Table 4-93
Location (Roller Cone Bits) [46]
N - Nose rows
Cone # or # s
M - Middle rows 1
H - Heel rows 2
A - All rows 3
Courtesy SPE
Table 4-94
Reason Pulled [46]
BHA - Change bottom hole assembly
DMF - Down hole motor failure
DSF - Drill string failure
DST - Drill stem test
DTF - Down hole tool failure
LOG - Run logs
CM - Condition mud
CP - Core point
DP - Drill plug
FM - Formation change
Courtesy SPE
HP - Hole problems
HR - Hours on bit
PP - Pump pressure
PR - Penetration rate
RIG - Rig repairs
TD -Total depthhasing depth
TQ - Torque
TW -Twist off
WC -Weather conditions