Drilling in the oil sands
The oil sands, located in northern Alberta, account for 97 percent of Canada’s oil reserves. Some of that oil is close to the surface and has to be mined, but most is deep underground and requires specialized technology to drill and pump it to the surface.
Currently, there are two main technologies used to access the oil from the reservoirs that are too deep to be mined: cyclic steam stimulation (CSS), which was the first technology to be used in the drilling process, and steam-assisted gravity drainage (SAGD, pronounced SAG-DEE), which is now the most common way to extract the oil. In 2012, there was twice as much oil produced using SAGD as was produced using CSS.
- Cyclic steam stimulation: a single-well process that injects high-pressure steam into the well over several weeks. Once the reservoir is filled with steam it’s left to soak for another several weeks to melt the oil and separate it from the sand. Oil is then pumped to surface in the same well that injected the steam.
- Steam-assisted gravity drainage: a two-horizontal-well process, with one well drilled in parallel above the other. Low-pressure steam is injected down the top well into the reservoir to melt the oil and separate it from the sand. The oil, along with the water from the cooled steam, drips into the bottom well and is pumped to the surface. The steam pressures used in SAGD don’t exceed the natural pressure that already exists underground.
All of Cenovus's oil sands projects use SAGD.
Watch a video of how SAGD works.