Oil sands are excavated using two primary methods: open-pit mining and in situ techniques, with open-pit mining used when the bitumen is near the surface.
Open-Pit Mining
Open-pit mining is used when the oil sands deposit is close to the surface, typically less than 75 meters deep. This method involves removing the topsoil and overburden (layers of rock and soil above the oil sands) to access the oil-rich sands.
Process of Open-Pit Mining:
- Clearing the Land: Vegetation and topsoil are removed.
- Overburden Removal: Large volumes of earth, rock and other materials are taken away using heavy machinery, such as trucks and excavators.
- Excavation of Oil Sands: Once the overburden is removed, the oil sand is extracted using giant shovels or draglines.
- Transportation: The extracted oil sands are then transported to a processing facility.
- Reclamation: After mining, the mined area is reclaimed, which involves contouring, replanting, and other efforts to restore the land.
According to the provided reference, approximately 20% of oil sands are recoverable through open-pit mining. This method is most effective for shallow deposits. The remaining 80% of oil sands requires alternative methods for extraction.
| Method | Depth | Percentage Recoverable |
|---|---|---|
| Open-pit Mining | Less than 75 meters | ~20% |
| In-situ Techniques | Greater than 75m | ~80% |
In Situ Techniques
In-situ techniques, which are not technically excavation methods are used to recover bitumen when the deposit is too deep to be mined. These techniques involve injecting steam or solvents into the oil sands to reduce viscosity of the bitumen so it can be pumped to the surface. In-situ extraction, unlike open pit mining, does not involve removing the oil sands from the ground.
