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Shrinking the Tailings Pond

Canadian Natural Resources Limited (Canadian Natural) is commercializing promising new ways to manage the tailings pond at its Horizon Oil Sands facility, 70 kilometers north of Fort McMurray. These new methods will require less storage space for fluid tailings, accelerate the process of reclamation and reduce greenhouse gas emissions.

The Horizon facility includes a surface mine and bitumen extraction plant with on-site bitumen upgrading and associated infrastructure to produce synthetic crude oil. The production of sweet crude oil results in solid and liquid wastes called tailings which are stored in a pond. Progressive reclamation of the tailings ponds (bringing the area back to its natural state) takes place throughout the life of the mine, which is approximately 40 years.

Currently at Horizon, waste carbon dioxide (CO₂) is being injected into the tailings slurry lines before the tailings enter the pond, where it reacts to form carbonic acid. This reaction changes the pH of the tailings mixtures and allows the fines clays, silts and sand to settle quickly and leave clearer water which can be immediately recycled for reuse in the bitumen extraction process.

During the next phase of Horizon development, another new tailings treatment process will be implemented by Canadian Natural. As part of this new process, cyclones will remove the water from the coarse sand and thickeners will remove the water from the fine clays, silts as well as sand. The dewatered streams will then be combined with waste CO₂ .The resultant tailings will be deposited in the tailings disposal area where even more water will be released and reused. Additionally the CO₂ will react with the minerals in the tailings to form
mineral carbonates.

These new processes will reduce the footprint of the tailings pond and by increasing the amount of water available for recycle, decrease the amount of river water needed to process bitumen. Canadian Natural expects this process of sequestering CO₂ into tailings will eliminate about 219,000 tonnes of CO₂ emissions every year.

After years of planning and building the facility, Horizon shipped its first synthetic crude oil in early 2009. The project is expected to have a life span of more than 40 years.