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Well Testing Toolbox
Interactive Tools
Engineering calculators and conversion utilities for field work.
API Gravity Correction (to 60°F)
Standardize oil density measurements using Hydrometer readings.
API @ 60°F
39.1
SG @ 60°F
0.8295
Density (kg/m³):
829.5
Documentation: API Correction
Scientific Equations
Standardized by ASTM D1250/1980.
- Specific Gravity: $$SG = \frac{141.5}{131.5 + API}$$
- Density (kg/m³): $$Density = SG \times 1000$$
How to Use
- Take your oil sample and use a Hydrometer to measure the observed API gravity.
- Record the Temperature of the oil at the exact moment of the API reading.
- Enter both values into the calculator to determine the Standard API at 60°F.
- Use the SG @ 60°F result for further reservoir engineering calculations.
Typical API Correction Table (Base 40 API)
| Observed Temp (°F) | Observed API | Corrected API @ 60°F |
|---|---|---|
| 70°F | 40.8 | 40.0 |
| 80°F | 41.6 | 40.0 |
| 90°F | 42.4 | 40.0 |
| 100°F | 43.2 | 40.0 |
*Rule of Thumb: API increases by ~0.08 for every 1°F increase in temperature.*
Scientific Documentation
The Math
Converting Observed API to Standard SG:
$$SG = \frac{141.5}{131.5 + API_{obs}}$$
Correction to 60°F using Volume Correction Factor (VCF):
$$API_{60} = \left( \frac{141.5}{SG_{obs} / VCF} \right) - 131.5$$
Instructor Field Guide
- Observation: Record the API from the hydrometer and the temperature from the thermometer immediately.
- Standardization: Use this tool to find the $60^\circ F$ equivalent for commercial reporting.
- Validation: If the corrected API is significantly different from previous samples, check the hydrometer for wax buildup.