BAKER HUGHES - Drilling Fluids Reference Manual

HYDRAULICS
where:
P n = total pressure-drop across bit, psi
ρ = fluid density, lb m /gal
Q = flow rate, gal/min
J n = nozzle size, 32nds of an in. (i.e., 11, 12, etc.).
Hydraulic Horsepower and Impact Force
Hydraulic horsepower is the product of pressure and flow rate, whereas impact force is the product
of fluid density, flow rate, and velocity. Both horsepower and impact are measures of the amount
of work from the drilling fluid available at the bit, although derived differently. Additionally, both
parameters are affected by the circulation pressure losses in all parts of the circulation system.
Hydraulic horsepower at the bit is given by:
where:
HHP = QP n
1714
HHP = hydraulic horsepower, hp
Q = flow rate, gal/min
P n = total pressure-drop across bit, psi.
Some operators prefer to analyze the ratio of hydraulic horsepower to hole area. This is
calculated by:
2 ( 1.2732)
HHP
HHP / in =
2
D
where:
Impact force is given by:
where:
HHP/in 2 = hydraulic horsepower per in.
D = hole size or bit size, in.
F i
ρ( Q)V = ------------------- n
1932
F i = impact force, lb f
ρ = fluid density, lb m /gal
Q = flow rate, gal/min
V n = nozzle velocity, ft/sec.
2
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 9-18