Managing Tailings

Corporate Responsibility

Managing Tailings

The continuous improvement of tailings management is an integral component of successful oil sands mining operations. Reducing the size and need for tailings ponds, and increasing the speed with which they can be reclaimed, are ongoing challenges being addressed by the industry.

Canadian Natural has taken significant steps to minimize the footprint of tailings. Our comprehensive land use planning considers the end of mine life so that we can manage our environmental closure programs and obligations, and advance reclamation as quickly as possible.

Canadian Natural has invested more than $3.5 billion in tailings research, technologies and project construction. Our tailings management technologies are the result of extensive research that can be applied on a commercial scale. This work exemplifies our approach to R&D, taking lab concepts through the pilot stage and on to commercialization.

What are tailings?

Tailings are a mixture of water, sand and clay found naturally in oil sands that remain following the mining extraction process. Tailings are transported by pipeline and deposited into ponds, where the majority of the solids – mostly sand – settle to the bottom. The remaining fluid (water and clay) is called Fluid Tailings (FT). As the solids in the FT begin to settle, the FT densifies, turning into a mixture called Mature Fine Tailings (MFT). Some of the MFT remain in tailings ponds, trapping water and reducing the amount of water available for recycling.

Many of our processes and new generation technologies focus on preventing FT formation from the outset, with the addition of carbon dioxide (CO2), and during the extraction process. For example, our In-Pit Extraction Process (IPEP) pilot produces dry, stackable tailings, avoiding the generation of FT. Read more about IPEP in the 2018 Stewardship Report to Stakeholders.

Advancing tailings management technologies

Our tailings management strategies align with regulatory requirements based on two key principles: 1) creating landforms that fit within the local landscape, and 2) supporting productive wetlands and boreal forest habitats. Our tailings management processes focus on preventing FT through optimizations and continuous improvements, dewatering tailings (increasing the release of water for recycling), and improving tailings consolidation over time, to ultimately accelerate the reclamation process.

At Horizon, we use a Non-Segregating Tailings (NST) process and CO2 injection. NST are tailings that have been significantly treated (dewatered) to form a homogeneous, semi-cohesive mass when deposited. The dewatering process is achieved by adding two steps to our original process: we use cyclones to separate the coarse sand and thickeners to capture fines and remove water in the tailings stream prior to being sent to the tailings pond. The warm water that is removed and recovered is then re-used in our bitumen extraction process. The coarse sand and thickener underflow are then mixed and further combined with CO2, which has been proven to accelerate the settling of the fines and NST as a whole.

At the Athabasca Oil Sands Project, we use thickeners and centrifugation technologies to help separate and remove water from the FT. In addition, an Atmospheric Fines Drying (AFD) technology at the Jackpine mine helps settle out solids in the FT, and we have composite tailings at the Muskeg River Mine. In 2018, several technologies were piloted, including filter bags to dewater tailings, centrifuge optimization trials (for long-term consolidation of treated fines) and enhancements to the AFD.

The environmental benefits of these tailings technologies are:

  • GHG emissions reduction through CO2 sequestration and less natural gas consumption.
  • Increase in fines capture, reducing tailings pond size and accelerating reclamation.
  • Increase in water recycling - CO2 sequestration and tailings technologies reduce fresh water use intensity and help maintain an 80% water recycle rate at our oil sands operations.

Canadian Natural is also investigating tailings reduction technologies that are designed to deal specifically with MFT, and tailings revegetation, such as the effects of NST on plants growth during reclamation. Along with other oil sands operators, we are researching the viability of pit lakes for treating process-affected water and sequestering tailings, as part of oil sands mine closure plans.

Throughout tailings research, planning and execution efforts, Canadian Natural has regularly engaged with stakeholders, in particular neighbouring communities, and we will continue to do so. Building on the foundation of our tailings management plan and our research, we strive to optimize resource recovery and reclaim the landscape.

Cyclones in the Horizon NST plant

Applied Process Innovation Centre (APIC) - The future of tailings

Testing and developing technological and process improvements in tailings management practices requires access to authentic samples, high quality industrial equipment and knowledgeable personnel familiar with mining operations. With ongoing research being a critical piece of our tailings management strategy, Canadian Natural built and commissioned the Applied Process Innovation Centre (APIC) at the Horizon site in 2015.

The 3,600-square-foot APIC provides a dedicated work space and resources for scientists and engineers to investigate and accelerate the application of tailings technologies to a commercial scale. It also facilitates research collaboration with other industry members directly and through COSIA. The research facility is primarily being used to further develop and improve tailings management methods, including thickened tailings production, NST, CO2 sequestration testing and MFT treatment.

CO2 capture and injection into tailings

Horizon's CO2 recovery plant has a capture capacity of 438,000 tonnes of CO2 annually — the equivalent of removing the emissions of 92,000 passenger vehicles from the road. Horizon’s CO2 capture plant is part of our hydrogen plant, which produces 144 million standard cubic feet per day of hydrogen that is used in secondary upgrading to stabilize the synthetic crude oil and reduce impurities.

The CO2 is added into the tailings stream before it enters the pond, where it creates a chemical reaction that changes the tailings water pH to be the same as river water. This reaction allows the solids (fines) to settle more quickly and for the quick release of clear and warm process water for recycling.

Left: Current tailings pond with CO2 added. Middle: Without the addition of CO2 the footprint of our tailings pond would be almost double the size. Right: Horizon CO2 recovery complex.