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Bit Hydraulics and Calculations Guide

The document discusses various calculations used for drilling operations involving bit design and performance. It provides formulas to calculate the pressure drop across the bit, impact force of jet nozzles on the hole bottom, cross flow velocity under the bit, nozzle velocity, total nozzle area, bit hydraulic horsepower, hydraulic horsepower per square inch of bit diameter, mechanical specific energy using both friction and torque, bit torque, and minimum flow rate for PDC bits - all in terms of various drilling parameters like flow rate, mud weight, nozzle number and area, bit diameter, weight on bit, rate of penetration, and torque.

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931 views1 page

Bit Hydraulics and Calculations Guide

The document discusses various calculations used for drilling operations involving bit design and performance. It provides formulas to calculate the pressure drop across the bit, impact force of jet nozzles on the hole bottom, cross flow velocity under the bit, nozzle velocity, total nozzle area, bit hydraulic horsepower, hydraulic horsepower per square inch of bit diameter, mechanical specific energy using both friction and torque, bit torque, and minimum flow rate for PDC bits - all in terms of various drilling parameters like flow rate, mud weight, nozzle number and area, bit diameter, weight on bit, rate of penetration, and torque.

Uploaded by

leopumpking
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Bit Calculations

Units
Where:
Pb = Bit Pressure Drop (lbs/in2) Vc = Cross Flow Velocity (ft/sec)
MW = Mud Weight (ppg) N = Number of Nozzles
Q = Flow Rate (gpm) Es = Specific Energy (psi)
An = Total Nozzle Area (in2) µ = Coefficient of Friction
Vn = Nozzle Velocity (ft/sec) ROP = Rate of Penetration (ft/hr)
HHPb = Horse Power at bit (hp) WOB = Weight on Bit (lbf)
HSI = Horse Power per inch (hp/in2) T = Torque (ft-lbs)
Db = Bit Diameter (in) Ah = Area of Hole (in2)
Ab = Area of Bit (in2) MSE = Mechanical Specific Energy (psi)
lfb = Impact Force at bit (lbf) Cd = Nozzle discharge coefficient

Pressure Drop Across Bit (psi) Impact of Jet Nozzles on Hole Bottom (lbf)
Calculated From Flow Rate, assumes Cd=1.0: Calculated From Velocity:

(MW)(Q ) 2
(Q)(MW)(Vn)
Pb = lfb =
(12,032)(An2) (1930)

Calculated From Velocity: Calculated From Pressure Drop:

(MW)(Vn ) 2
lfb = 0.0173Q [PbMW] 1/2
Pb =
(1,239)
Cross Flow Velocity under the Bit (ft/sec)
Bit Nozzle Velocity (ft/sec) (108.5) (Q)(Vn) 1/2
Calculated From Flow Rate: Vc = [ (NDb ) ]
(Q )
Vn = (0.321)
(An) Mechanical Specific Energy using µ (psi)
1 (13.33)(µ)(RPM)
Calculated From Pressure Drop:

(1,239 )(Pb ) 1/2


MSE =WOB
Ab
+[ (ROP)(Db) ]
Vn = [ (MW) ] Bit Aggressiveness/Coefficient of Friction
36(T)
Total Bit Nozzle area (in2)
Calculated From Bit Pressure Drop:
µ= [(WOB)(Db) ]
(MW )(Q2 ) 1/2
An = [
(12031)(Pb) ] Mechanical Specific Energy using Torque (psi)
An = ∑(An1+ An2 + ...Anx ) 480(T)(RPM) 1.274(WOB)
MSE = +
ROP(Db2) (Db2)

Bit Hydraulic Horsepower (hp) Bit Torque (ft-lbs)


Hydraulic HP by Bit Nozzles:
µ(Db)(WOB)
(Pb )(Q) T=
HHPb = 36
(1714)

Hydraulic HP per sq. in. of Bit Diameter: Minimum Flow rate for PDC Bits (gpm)
(HHPb)(1.273) GPM = 12.72Db1.47
HSI =
(Db ) 2

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