Managing Tailings - Horizon Oil Sands

Corporate Responsibility

Managing Tailings - Horizon Oil Sands

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 invested more than $1.9 billion in tailings research, technologies and project construction at Horizon. Our tailings management technologies are the result of extensive research that can be applied at commercial scale. This exemplifies our approach to research and development and how we take technologies from pilot project to commercialization. These innovative methods will accelerate the process of reclamation by increasing water recycling and reducing the tailings footprint, while also reducing carbon dioxide (CO2) emissions.

What are tailings?

Tailings are the sand, silt, clay and water found naturally in oil sands that remain following the mining and bitumen extraction process. Tailings are transported by pipeline and deposited in ponds where the majority of the solids – mostly sand – settle to the bottom. The remaining fluid – water, with some clay and silt – 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 remains in tailings ponds, trapping water and reducing the amount of water available for recycling.

Advancing tailings management technologies

Our tailings management strategies align with regulatory requirements based on two key aspects: 1) creating a solid landform that fits within the local landscape, and 2) supporting productive wetlands and boreal forest habitat.

To do this, we are proactively managing the fines before they become part of the fluid tailings by using a Non-Segregating Tailings (NST) process that includes CO2 injection. These processes combined are the foundation of our tailings management plan.

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 and remove water from the fines in the tailings stream prior to be sent to the tailings pond. The warm water that is removed and recovered is then re-used in our bitumen production 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.

Canadian Natural is also investigating tailings reduction technologies that are designed to deal specifically with MFT, by reducing the amount of fines in the process.

We continued to make significant progress during 2016:

• further decreased the amount of fines going to the tailings pond and forming FT as a result of selective lower fines mining practices;

• increased fines capture and decreased fluid tailings production, which is expected to continue improving as we ramp up NST deployment performance;

• through a number of initiatives, we increased water recycling by 10% from 2015, reducing our water intake from the Athabasca River;

• reduced GHG emissions due to the increase in warm process water recycling during the NST process, as the water does not need to be re-heated;

• Horizon’s new CO2 capture plant will recover 50 tonnes/hour of CO2 that will be injected into the tailings; and,

• initiated research and engineering of NST reclamation, planting vegetation directly into the NST to determine plant growth, for future planting on topsoil and subsoil capped NST.

As part of our strong commitment to continuous improvement, we investigate new ideas and build on lessons learned. Our plan includes what we learned from our processes, and the technologies developed by our peers and shared through Canada’s Oil Sands Innovation Alliance (COSIA).

Cyclones in the Horizon NST plant

Addition of CO2 into tailings

Horizon Oil Sands has been adding purchased CO2 to tailings since 2009 to enhance solids settling rates, keeping the pond at roughly half the size it would have been without that process. 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 the same as river water, allowing the solids to settle more quickly. This accelerated settling enables the quick release of clear and warm process water for recycling.

Horizon's CO2 recovery plant will have the capacity to capture 438,000 tonnes of CO2 annually - the equivalent of removing the emissions of 92,000 passenger vehicles from the road. Horizon’s new plant will also produce a total of 144 million standard cubic feet per day of hydrogen, doubling Horizon’s current hydrogen capacity. Hydrogen is used in secondary upgrading to stabilize the synthetic crude oil and reduce impurities.

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. Left: Horizon hydrogen and CO2 recovery plants.

The future of tailings: Horizon's Research Centre

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. The Applied Process Innovation Centre (APIC) is a 3,600 square foot research facility at Horizon site that offers all of this. Operational since June 2015, APIC is a dedicated work space to investigate and accelerate the application of tailings technologies to commercial scale.

The facility is primarily being used to further develop and enhance tailings management methods, including thickened tailings production, NST, CO2 sequestration testing and MFT treatment. This facility also facilitates collaboration on research projects with industry, academia and government. For more information, read our 2016 Stewardship Report to Stakeholders.

A member of our Process Innovation team conducting tests at the new Applied Process Innovation Centre.

Tailings Oil Analyzer

Canadian Natural is using Tailings Oil Analyzer (TOA) units in our Horizon operations to reduce the amount of bitumen that reaches the tailings pond. The (TOA) is an on line instrument that continuously monitors the bitumen content of a tailings stream.

The TOA works by evaluating a sample of the tailings stream and measuring the level of light absorption. The analysis generates important data regarding how much oil is present in the stream. This enables our Operations team to adapt to the readings and make quick, real-time operational decisions for production process adjustments, resulting in operational savings and improved bitumen recovery. The development of the technology was completed in partnership with Alberta Innovates.

TOA panel (left) and control room (right) at Horizon

Through a committed effort to continuous improvement, Horizon is achieving extremely important environmental and efficiency objectives. These accomplishments are important for the oil sands industry as a whole, which sees producers collaborating to accelerate the pace at which we can all enhance environmental performance.