STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Downhole Motors 895
3000
.-
n
v)
a
U
v)
0 2000
-I
a
L.
3
v)
v)
2
a 1000
-
c m
0
!-
0
q (QPm)
Figure 4-208. 6-in. liner, total pressure loss vs. flowrate, Example 4.
(Courtesy Smith International, Inc.)
the allowable maximum pressure for the particular liner size. The vertical
straight line is the allowable maximum volumetric flowrate for the particular
liner size. Only circulation flowrates that are in the lower left quadrant of the
figures are practical. The highest circulation flowrate (which produces the
highest positive displacement motor horsepower) is found in Figure 4-209, the
6%-in. liner. The optimal circulation flow rate is 348 gal/min.
Positive Displacement Motor Performance. Using the positive displacement
motor performance data in Table 4-114 and the scaling relationships in Equations
4-168 through 4-170, the performance graph for the positive displacement
motor operating with a circulation flowrate of 348 gal/min can be prepared.
This is given in Figure 4-213.
Bit Nozzle Sizes. The pressure loss through the bit must be 500 psi with a
circulation flowrate of 348 gal/min with 11.6-lb/gal mud weight. The pressure
loss through a roller rock bit with three nozzles is (see the section titled “Drilling
Bits and Downholes Tools”)
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