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 $1.6 billion in tailings management research and technologies to date. Our investments in tailings management technologies demonstrate our approach to research and development and how we take technologies from pilot project to commercialization. Canadian Natural is using and also researching new processes to reduce the footprint of the Horizon tailings pond and the amount of fresh water required for bitumen processing. These innovative methods will accelerate the process of reclamation, increase water recycling and reduce carbon dioxide (CO2) emissions.

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 – mostly clay, silt and water – flows to the middle of the pond. This mixture is called Fluid Fine Tailings (FFT). As the solids in the FFT begin to settle it becomes thicker, turning into a mixture called Mature Fine Tailings (MFT). MFT remain in tailings ponds while the solids continue to settle and the water evaporates.

Advancing tailings management technologies

The processing of bitumen extracted from mining requires the operation of tailings facilities to manage the water used in processing. In 2015, we commenced production of non-segregating tailings (NST) at Horizon. NST are tailings that have been significantly treated (dewatered) to form a homogeneous, semi-cohesive mass when deposited. The treatment process includes cyclones, to separate the coarse sand, and thickeners, to capture and remove water from the fines in the tailings streams prior to being sent to the tailings pond. The warm water that is removed and recovered is then re-used in the bitumen recovery process. The coarse sand and thickener underflow are then mixed and further combined with CO2 to produce NST. The addition of CO2 to NST has been proven to accelerate the settling of the clay fines in the tailings stream.

The NST process and our ongoing pilots to reduce MFT are enhancing the production of dry, solid tailings to ultimately reduce our environmental footprint and accelerate land reclamation. Using NST also allows warm process water to be recycled before it cools; reducing the amount of energy and greenhouse gases required to reheat the water for use in our bitumen extraction process. We are also decreasing the amount of fines going to the tailings pond by using smaller equipment and a selective mining process.

For more information on our tailings management technologies, read our 2015 Stewardship Report to Stakeholders.

Addition of CO2 into tailings

Horizon has been adding 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.

Canadian Natural has been purchasing waste CO2 to add into the tailings stream, however a CO2 capture plant is being built that will be capable of supplying the required CO2 for tailings management. The CO2 capture plant at Horizon will be operational in 2016 and will have the capacity to capture 438,000 tonnes of CO2 annually – the equivalent of removing the emissions of 77,000 cars 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. Without the addition of (CO2) the footprint of our tailings pond would be almost double the size. Left: Horizon hydrogen and (CO2) recovery plants under construction.

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. The Applied Process Innovation Centre (APIC) is a 3,600 square foot research facility at Canadian Natural’s Horizon Oil Sands site that offers all of this. Operational since June 2015, APIC is a dedicated and secure work space to investigate tailings management methodologies.

The APIC was designed and equipped to perform a variety of tailings tests and programs including analysis of mixing systems, evaporation and drying analysis, production of NST for testing, and production of thickened tailings. Various measurements can be performed quickly and effectively with fast turnaround of results and subsequent decisions. 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.

 

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

Tailings Oil Analyzer

The Tailings Oil Analyzer (TOA) is another emerging technology in the oil sands industry. The TOA is an on line instrument which can continuously monitor the bitumen content of a tailings stream. Canadian Natural is using a TOA unit in our Horizon operations to reduce the amount of bitumen that reaches the tailings pond.

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 decisions on adjustments to the production process, resulting in operational savings and improved bitumen recovery. The development of the technology was completed in partnership with Alberta Innovates Technology Futures (formerly known as the Alberta Research Council).

 

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 now sees producers collaborating to accelerate the pace at which we can all enhance environmental performance.