STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

AP5 = [
0.729
(2.4)(118.62) (2)(0.729)+ 1 ] (0.433)( 4000)
(8.835- 4.5) (3)(0.729) (300)(8.835- 4.5)
= 32.0 psi
The total frictional pressure loss is
Apf = 94.32 + 243.23 + 32.27 + 9.51 + 32.0 = 411.33 psi
Pressure Loss through Bit Nozzles
Drilling Mud Hydraulics 839
Assuming steady-state, frictionless (due to the short length of the nozzles)
drilling fluid flow, Equation 4-102 is written
av
pv- = - ap
(4-116)
ai ai
Integrating Equation 4-1 16 assuming incompressible drilling fluid flow (p is
constant) and after simple rearrangements yields the pressure loss across the
bit Ap,(psi) which is
pvp
Ap = - (4-117)
b 2
Introducing the nozzle flow coefficient of 0.95 and using field system of units,
Equation 4-1 17 becomes
7VZ
AP,, = -
1,120
(4-118)
or
7q2
= 10, 858A2
(4-1 19)
where v = nozzle velocity in ft/s
q = flow rate in gpm
7 = drilling fluid density in lb/gal
A = nozzle flow area in in.2
If the bit is furnished with more than one nozzle, then
(4- 120)
where n is the number of nozzles, and
den =dd;+di+ ... dz
(4-12 1)
where den is the equivalent nozzle diameter.