Basic Calculators
Foundational ESP calculations covering pressure-to-head conversion, cable voltage drop, pump affinity laws, electrical power calculations, and total dynamic head.
Pressure to Feet of Head
Converts between pressure (PSI) and vertical fluid column height (feet). This relationship depends on the specific gravity of the wellbore fluid.
Where:
PSI = Pressure in pounds per square inch
Feet = Vertical height of fluid column
SG = Specific gravity of fluid (water = 1.0)
2.31 = Conversion factor (ft of water per PSI)
Typical Fluid Specific Gravities
| Fluid Type | Typical SG Range | Notes |
|---|---|---|
| Fresh Water | 1.00 |
Reference baseline |
| Produced Water (Permian) | 1.02 – 1.15 |
Varies with TDS; Delaware Basin often higher |
| Light Crude Oil | 0.82 – 0.88 |
35–45° API |
| Medium Crude Oil | 0.88 – 0.92 |
25–35° API |
| Mixed Emulsion | 0.90 – 1.05 |
Depends on water cut and emulsion stability |
Field Tip: Intake pressure gauges read total fluid column above the sensor. To get fluid level above pump, account for gauge depth vs. pump depth, and use the actual produced fluid SG—not water.
Cable Voltage Drop
Calculates voltage loss in ESP power cable due to conductor resistance. Critical for ensuring adequate voltage reaches the downhole motor, especially in deep wells or high-current applications.
Where:
Vdrop = Voltage drop (volts)
I = Motor current (amps)
R = Conductor resistance (ohms per 1000 ft)
L = Cable length (feet)
2 = Round-trip factor (accounts for return path in 3-phase)
Conductor Resistance Values
Resistance values at 77°F (25°C) for copper conductors. Actual downhole resistance increases with temperature—approximately 0.4% per °C above reference.
| AWG Size | Ω per 1000 ft (77°F) | Typical Application |
|---|---|---|
| 14 AWG | 2.525 |
Low-power, shallow wells |
| 12 AWG | 1.588 |
Light-duty applications |
| 10 AWG | 0.999 |
Standard residential/light commercial |
| 8 AWG | 0.628 |
Common oilfield size |
| 6 AWG | 0.395 |
Standard oilfield size |
| 4 AWG | 0.249 |
Higher-power applications |
| 2 AWG | 0.156 |
High-power, deep wells |
| 1 AWG | 0.124 |
Maximum power applications |
Temperature Correction
For accurate downhole calculations, correct resistance for operating temperature:
Where:
RT = Resistance at operating temperature
R25 = Resistance at 25°C (77°F)
T = Operating temperature (°C)
0.00393 = Temperature coefficient for copper
Affinity Laws
The affinity laws describe how centrifugal pump performance changes with speed. Essential for predicting ESP behavior when adjusting VSD frequency.
Where:
Q = Flow rate (BPD or GPM)
H = Head (feet)
P = Power (HP or kW)
N = Rotational speed (RPM or Hz)
Subscript 1 = Original condition
Subscript 2 = New condition
Key Relationships
- Flow varies linearly with speed (1:1)
- Head varies with the square of speed (reduces faster than flow when slowing down)
- Power varies with the cube of speed (significant savings at reduced speed)
Example: Reducing frequency from 60 Hz to 50 Hz (83% speed) results in: 83% of original flow, 69% of original head, and only 58% of original power draw.
KVA / KW / HP Conversions
Three-phase electrical power calculations for ESP motor sizing and load analysis.
Where:
V = Line voltage (volts)
I = Line current (amps)
√3 = 1.732 (three-phase factor)
PF = Power factor (typically 0.80–0.90 for ESP motors)
0.746 = kW per HP conversion
Back-Calculations
The calculator also supports working backwards from motor HP to derive current:
Total Dynamic Head (TDH)
Total head the ESP must generate, combining static lift, friction losses, and discharge pressure.
Where:
Hstatic = Vertical lift (pump depth minus fluid level)
Hfriction = Tubing friction losses
Hdischarge = Surface discharge pressure converted to feet
Component Breakdown
- Static Head: The vertical distance fluid must be lifted. In most calculations, this is measured from the pump intake to surface, minus the fluid level above the pump.
- Friction Head: Energy lost to tubing friction. Depends on flow rate, tubing ID, and fluid viscosity. Can be estimated using Hazen-Williams or Darcy-Weisbach equations.
- Discharge Head: Back-pressure at surface (flowline pressure, separator pressure) converted to feet of fluid.
Quick Estimate: For most Permian unconventional wells, friction losses in 2-7/8" tubing at moderate rates (500–1500 BPD) are 5–15% of total TDH. Always calculate explicitly for high-rate or viscous fluid cases.
Related Documentation
- Tubing Capacity Calculator — Fluid volumes and annular space
- Gas Handling — GVF effects on pump performance
- All Documentation