STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

876 Drilling and Well Completions
Table 4-113
Drill String Component Pressure Losses at
Various Circulation Flowrates for Example 2
Pressure (psi)
Components 200 gpm 300 gpm 400 gpm 500 gpm
Surface Equipment 4 11 19 31
Drill Pipe Bore 460 878 1401 2021
Drill Collar Bore 60 117 118 272
Turbine Motor 536 1207 2145 3352
Drill Bit 729 486 364 292
Drill Collar Annulus 48 91 144 207
Drill Pipe Annulus 133 248
391 561
-
-
- -
Total Pressure Loss 1970 3038 4652 6736
Total Flow Area for Bit. Knowing the optimal circulation flowrate, the actual
pressure loss across the bit can be found as before in the above. This is
APb =
85.05( 1,714)
340
= 429 psi
With the flowrate and pressure loss across the bit, the total flow area of the
diamond bit A, (in.2) can be found using [88]
(4-153)
where ROP = rate of penetration in ft/hr
Nb = bit speed in rpm
The bit speed will be the optimum speed of the turbine motor, 685 rpm. The
total flow area A,, for the diamond bit is
(340)' 16.2
1/2
Ad = [ 8795( 429) ] 0.9879
= 0.713 in.2
1
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