Crude oils are often classified according to their density and their sulfur content.
- Heavy: Oils with a high density (low API gravity).
- Light: Oils with a low density (high API gravity).
- Sweet: Oils with a low sulfur content.
- Sour: Oils with a high sulfur content.
While these terms are used throughout the industry, there are no precise, universally accepted specifications for what constitutes a “sweet” versus a “sour” crude, or a “light” versus a “heavy” one.
The figure below may be used as a general guideline. It is drawn based on a useful classification adopted by ENI’s R&M Division Research Center for Downstream Technologies.
Sources: ENI World Oil and Gas Review 2007, ENI Strategies and Development Department.