Drilling Technology

Bit Nozzle Selection Optimised Hydraulics

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These series of formulas will determine the correct jet sizes when optimising for jet impact or hydraulic horsepower and optimum flow rate for two or three nozzles.

1. Nozzle area, sq in.: Nozzle area, sq in. = N12 + N22 + N32
2. 8
3. Bit nozzle pressure loss, psi (Pb): Pb = gpm2 x MW, ppg

10858 x nozzle area, sq in.2

1. Total pressure losses except bit nozzle pressure loss, psi (Pc): Pci & Pc2 = circulating pressure, psi — bit nozzle pressure Loss.
2. Determine slope of line M: M = log (Pcr- Pc?)

log (Q1 - Q)

1. Optimum pressure losses (Popt)
2. For impact force: Popt = 2 x Pmax

b) For hydraulic horsepower: Popt = 1 x Pmax

1. For optimum flow rate (Qopt):
2. For impact force: Qopt, gpm = (Popt )1 - M x Q1

Pmax b) For hydraulic horsepower: Qopt, gpm = (Popt )1 - M x Q1

Pmax

1. To determine pressure at the bit (Pb): Pb = Pmax — Popt
2. To determine nozzle area, sq in.: Nozzle area, sq in. = V Qopt2 x MW, ppg

10858 x Pmax

9. To determine nozzles, 32nd in. for three nozzles:

10. To determine nozzles, 32nd in. for two nozzles:

Example: Optimise bit hydraulics on a well with the following:

Select the proper jet sizes for impact force and hydraulic horsepower for two jets and three jets:

DATA: Mud weight = 13.0 ppg Maximum surface pressure = 3000 psi Pump rate 1 = 420 gpm Pump pressure 1 = 3000 psi

Pump rate 2 = 275 gpm Pump pressure 2 = 1300 psi

Jet sizes = 17-17-17

1303.8

Nozzle area, sq in. = 0.664979

2. Bit nozzle pressure loss, psi (Pb):

10858 x 0.6649792

10858 x 0.6649792

3. Total pressure losses except bit nozzle pressure loss (Pc), psi:

4. Determine slope of line (M):

M = 0.3623309 0.1839166 M = 1.97

1. Determine optimum pressure losses, psi (Popt):
2. For impact force: Popt = 2 x 3000
3. 97 + 2 Popt = 1511 psi b) For hydraulic horsepower: Popt = 1 x 3000
4. 97 + 1 Popt = 1010 psi
5. Determine optimum flow rate (Qopt):
6. For impact force: Qopt, gpm = (1511) 197 x 420

3000 Qopt = 297 gpm b) For hydraulic horsepower: Qopt, gpm = (1010) K 197 x 420

3000 Qopt = 242 gpm

1. Determine pressure losses at the bit (Pb):
2. For impact force: Pb = 3000 psi — 1511 psi

Pb = 1489 psi b) For hydraulic horsepower: Pb = 3000 psi — 1010 psi

Pb = 1990 psi

1. Determine nozzle area, sq in.:
2. For impact force: Nozzles area, sq. in. = V 2972 x 13.0

10858x1489

Nozzles area, sq. in. = V 0.070927 Nozzle area, = 0.26632 sq. in.

b) For hydraulic horsepower: Nozzles area, sq. in. = V 2422 x 13.0

10858x1990

Nozzles area, sq. in. = V 0.03523 Nozzle area, = 0.1877sq. in.

1. Determine nozzle size, 32nd in.:
2. For impact force: Nozzles = V 0. 26632 x 32

b) For hydraulic horsepower: Nozzles = V 0.1877 x 32

NOTE: Usually the nozzle size will have a decimal fraction. The fraction times 3 will determine how many nozzles should be larger than that calculated.

so: 1 jet = 10/32nds 2 jets = 11/32nds b) For hydraulic horsepower: 0.03 x 3 = 0.09 rounded to 0

so: 3 jets = 9/32 nd in.

1. Determine nozzles, 32nd in. for two nozzles:
2. For impact force: Nozzles = V 0. 26632 x 32

2 x 0.7854

b) For hydraulic horsepower: Nozzles = V 0.1877 x 32

2 x 0.7854

0 0