1. Basic Formulas

Table of Content

1. Pressure Gradient
2. Hydrostatic Pressure
3. Converting Pressure into Mud Weight
4. Specific Gravity
5. Equivalent Circulation Density
6. Maximum Allowable Mud Weight
7. Pump Output
8. Annular Velocity
9. Capacity Formulas
10. Control Drilling
11. Buoyancy Factor
12. Hydrostatic Pressure Decrease POOH
13. Loss of Overbalance Due to Falling Mud Level
14. Formation Temperature
15. Hydraulic Horsepower
16. Drill Pipe, Drill Collar Calculation
17. Pump Pressure, Pump Strokes
18. Cost Per Foot
19. Temperature Conversion Formulas

1.10 Control Drilling

Maximum drilling rate (MDR), ft/hr, when drifting large diameter holes (14- 3/4 in. and larger)

$\mathrm{MDR,\; ft/hr}=\frac{67\times (\mathrm{mud\; weight\; out,\; ppg}-\mathrm{mud\; weight\; in,\; ppg})\times \mathrm{circulation\; rate,\; gpm}}{{\mathrm{Dh}}^2}$

Example: Determine the MDR, ft/hr, necessary to keep the mud weight coming out at 9.7 ppg at the flow line:
Data: Mud weight in = 9.0 ppg, Circulation rate = 530 gpm, and, Hole size = 17-1/2 in.
MDR, ft/hr 2.4
$\mathrm{MDR,\; ft/hr}=\frac{67\times (9.7-9.0)\times 530}{{17.5}^2}$
$\mathrm{MDR,\; ft/hr}=\frac{67\times 0.7\times 530}{{17.5}^2}$
$\mathrm{MDR,\; ft/hr}=\frac{24.857}{306.25}$
MDR = 81.16 ft/hr

⬆ Table of Content