STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

HP, = 217( -) 1421
2842
Downhole Motors 873
= 108.5
and from Equation 4-149 for the 14-lb/gal mud weight
HP, = 108.5( $)
= 152
Pressure Drop. Table 4-110 shows that the 212-stage turbine motor has a
pressure drop of 1,324 psi for the circulation flowrate of 400 gal/min and a
mud weight of 10 lb/gal. The pressure drop for the 106 stage turbine motor
should be roughly proportional to the length of the motor section (assuming
the motor sections are nearly the same in design). Thus the pressure drop in the
106-stage turbine motor should be proportional to the number of stages.
Therefore, the pressure drop should be
= 662 psi
and from Equation 4-151 for the 14-lb/gal mud weight
Ap = 662( s)
= 927 psi
The last column in Tables 4-110 and 4-111 show the thrust load associated
with each circulation flowrate (Le., pressure drop). This thrust load is the result
of the pressure drop across the turbine motor rotor and stator blades. The
magnitude of this pressure drop depends on the individual internal design
details of the turbine motor (i.e., blade angle, number of stages, axial height of
blades and the radial width of the blades) and the operating conditions. The
additional pressure drop results in thrust, T (lb), which is
T = xriAp (4-1 52)
Example 2
A 6$-in. outside diameter turbine motor (whose performance data are given in
Tables 41 10 and 41 11) is to be used for a deviation control direction dritling operation.
The motor will use a new 8-$-in. diameter diamond bit for the drilling
operation. The directional run is to take place at a depth of 17,552 ft (measured