STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

786 Drilling and Well Completions
Similar calculations are made for each bit run and recorded on the bit record.
The bit record is presented in Table 4-97. Inserts were run below 6500 ft. Costper-foot
data was calculated for each bit and is presented.
From Table 4-98 insert bits drilled 1132 ft at a cost of $17,205.00.
Cost of conventional bits from the offset well were $27,803.00.
Savings with inserts: $10,597.00.
Roller Rock Bit Hydraulics
Roller rock bit nozzle sizes are given in Table 4-98. The total pressure drop
across a roller rock bit, P,(psi), is [47]
P, = Ymq2
7430C2(d: + d: + d:)'
(4-76)
where 7 = specific weight of drilling mud in lb/gal
q = volumetric rate of flow of drilling mud through the bit in gal/min
d,, d,, d, = the diameters of the three bit nozzles, respectively in in,
C = the nozzle coefficient (usually taken to be about 0.98 or else)
Table 4-97
Cost of Insert Bits [34]
Bit No Depth out, ft Footage, ft Bottom time, hr
1 5958 160 10.5
2 9260 302 19.0
3 6329 69 3.5
4 6469 140 15.5
5 6565 96 9.5
6 6692 127 9.0
7 6873 181 15.5
8 7031 158 16.0
9 7180 149 18.5
10 7243 63 11.0
11 7295 52 11.0
12 7358 53 12.5
13 7425 67 12.5
14 7460 35 10.0
15 7527 67 10.5
Copyright PennWell Books, 1986.
Table 4-98
Jet Nozzles Sizes
lnches(32's) 8 9 10 11 12 13 14 15 16 18 20 22 24 26 28
Millimeters(mm) 6.4 7.1 7.9 8.7 9.5 10.3 11.1 11.9 12.7 14.3 15.9 17.5 19.0 20.6 22.2