Medium density hydrocarbon that stay liquid or semi-solid liquid in subsurface reservoir.
The usual composition ranges from C1 to C16 and API gravity is between 10° and 42°.
It may also include minor organic and inorganic chemical substances (< 7% in weight).
The total range of oil density is often classified in narrow ranges:
| Light Oil | Medium Oil | Heavy Oil | Extra Heavy Oil (Bitumen) |
|---|