A standard barrel of oil contains 42 gallons. This is the U.S. measurement that has been used since the 1800s, as it was the volume of a standard wooden barrel used for hauling many types of liquid. To measure production output, barrels of oil are grouped into classifications by one thousand barrels, one million barrels, and one billion barrels.
There are other international measurements such as 159 liters using the metric system or 35 imperial gallons from the U.K. measurement system.
As the oil industry evolved, the focus changed simply from volume to density, as density is a better indicator of the value.
How Do You Account for Light vs. Heavy Oil?
To achieve an accurate measurement of the amount of oil in a barrel, you need to calculate the density of the oil.
Density is weight per unit of volume and changes with changes in pressure and temperature. The API standard for pressure is 14.696 psi and 60 degrees Fahrenheit for temperature. This is considered the base condition for a standard amount of oil that occupies one barrel of oil. If the pressure is higher or lower, the volume would remain the same, but the mass would change.
The indicator of the lightness or heaviness of the oil is the API gravity, which is measured as the inverse of the density relative to water. Oil is bought and sold based on volume and API density at standard conditions.
- Lighter oils have a higher API gravity
- Heavier oils have a lower API gravity
Once you determine the API gravity of oil, you can use formulas to calculate density. The calculations are used by industry to increase accuracy and repeatability in measurement.
Receive Training on How to Accurately Measure Oil
Measurement professionals need to have a fundamental understanding of how to perform an accurate measurement of oil. The key components include:
- Volume gauging
- Temperature determination
- API gravity determination
- Water determination
- Proving (Mass, Volumetric, and Meters)
GCI offers a Fundamentals of Crude Measurement training course to help measurement professionals understand measurement concepts, how to perform accurate calculations, and how to use available tools in the field.
Contact us today to inquire about our next training in Houston, Texas.