A soft, clay-rich material is produced after spinning fine tails through centrifuges.
At Syncrude, tailings are a byproduct of our process to extract bitumen from oil sand. Tailings are composed of a mixture of water, sand, clay, fine solids, residual hydrocarbon and salts – all of which are naturally found in oil sands deposits.
Tailings are placed in large landforms commonly referred to as settling basins or tailings ponds. Tailings ponds serve two uses – one, as the recycled water source for our plants and, two, as a containment area which enables tailings to segregate prior to further dewatering for use in reclamation activities.
The primary tailings management challenge is the long period of time it takes for some solid components to settle. While the sand settles rapidly, clay and fine solids (together called fluid fine tailings or FFT) can take decades to settle on their own.
Over 85% of the water used in the bitumen extraction process is recycled from our tailings settling basins.
In the settling process, water rises to the top of the tailings pond and is then reused in the bitumen extraction process. Over 85 percent of the water we use is recycled from our settling basins. The Mildred Lake Settling Basin and Aurora Settling Basin are the main sources of recycled water for our operation.
Tailings also contain bitumen that is not recovered in the extraction process. As the bitumen is released, it floats to the top of the settling basin and can appear as an oily slick on the water surface. Bird deterrents are in place year-round to discourage waterfowl from landing.
Bitumen is a valuable natural resource and, while recovery is about 90 percent, we are studying new technologies and processes to increase this even further. This will reduce the amount of bitumen lost to tailings.
- Tailings are transported via pipeline to the settling basin.
- Sand settles quickly to the bottom of the basin.
- Fine solids, such as clay and silts, create a floating layer called fluid fine tailings.
- Mature fine tailings, which contain heavier fine solids, form underneath the layer of fluid fine tailings.
- Water is released from the tailings during the settling process.
- Released water is recycled for use in plant operations.
- Seepage and precipitation runoff are collected and pumped into the pond through a series of interceptor ditches and sumps.
- An extensive deterrent system is in place to protect birds and animals from coming in contact with bitumen.