Steam-Assisted Gravity Drainage
The Athabasca oil sands in Northern Alberta are one of the world's largest known petroleum resources. These resources lie under 141,000 square kilometres outside of Fort McMurray and, according to Alberta Energy, contain over 170 billion barrels of oil. This makes it the third largest oil reserve in the world after Saudi Arabia and Venezuela.
The challenge Canadian oil producers face with getting this oil is that it doesn’t come in the liquid form we put in our cars every day; it comes in the form of a heavy, viscous substance known as bitumen. Trapped 75 to 100 metres below the surface, bitumen was thought to be impossible or too costly to recover, but PetroChina Canada is using a leading-edge technology - SAGD - to do just that.
What is SAGD?
Steam-assisted gravity drainage. It's a specific process used to soften deposits of bitumen and heavy crude oil in the ground. Steam is pumped into the ground to separate the bitumen from the rock so that it can be pumped to the surface. Think of un-steamed bitumen as cold peanut butter out of the fridge versus steamed bitumen as microwaved peanut butter. The SAGD process softens the consistency of the bitumen so it moves and pumps easily to the surface.
How does it work?
- Two horizontal wells are drilled parallel to each other underground, approximately five metres apart. The top well is called the injection well, the lower one the production well. Once the holes are drilled, cylindrical casings are sent down the wells.
- Once the casings are in place, steam generated by boilers is sent into the ground through the installed pipes. The steam softens the bitumen to the point where it separates the oil from the rock.
- Once heated, the deposit liquefies enough that gravity pulls it down into the production well
- After the deposit is collected in the lower production well, it's transported using a pumping system to the central plant
- The water that'sheated and injected into the well as steam eventually cools and runs into the production well. We pump the water and oil mixture to the surface where we separate them. The water is recycled and treated so 90% of it can be reused in the process.
- The remaining oil is then shipped by pipeline to refineries across North America where it's processed into usable products like gasoline, diesel and jet fuel
What are the benefits of SAGD?
The environmental footprint of the SAGD process is far less than mining. Using SAGD we're getting under the ground without disrupting everything that is going on above the ground. There's significantly less damage to trees, plants and grass, and animals in the area are less disturbed by the process.
While some other oil companies also use SAGD technology, PetroChina Canada is always looking for ways to enhance the SAGD process. Our team is continually increasing recovery rates, creating greater efficiencies and making the process as environmentally friendly as possible.