Tailings are a by-product of Syncrude’s process to extract bitumen from oil sand. They are composed of water, sand, clay and other substances naturally found in oil sands deposits, and are stored in mined-out areas and large above-ground containment structures called settling basins or tailings ponds. Tailings ponds play an important role in oil sands mining operations by recycling process water, which minimizes consumption of fresh water. The primary tailings management challenge is the long period of time – several decades – that it can take for the fine clay and solids to settle.
In 2010, Syncrude became the first operating mine to receive approval for a tailings management plan designed to meet the long-term intent of stringent new regulations for drastically accelerating reclamation of tailings ponds called Directive 074. Syncrude’s plans to incorporate a multi-pronged approach that employs the following three technologies:
- Composite tails or “CT”: CT mixes mature fine tails with sand and gypsum to accelerate the separation of water from the clay. The CT is then capped with sand and soil, enabling the creation of landscapes that support grass, trees and wetlands.
- Water capping: A layer of fresh water is placed over MFT to form a lake. This technology is supported by over 20 years of research and pilot projects, the largest of which was 4 hectares.
- Centrifuging: Putting tailings through vessels where a spinning action separates out the water. Released water will be recycled for plant operations. This technology produces a soft, clay-rich soil that can be used as a landform foundation in oil sands reclamation areas. We are implementing centrifuge technology in two stages - a commercial-scale plant began operations in 2012 and a full-scale commercial plant is targeted to be in service in 2015.
Other methods, such as accelerated dewatering, are also being explored.
Syncrude also participates in the Canadian Oil Sands Innovation Alliance, an industry consortium formed to share best practices and advance innovative tailings management technologies.
More information about Directive 074 is available at www.ercb.ca.
Dried tails after centrifuging processing.