- Contributed to technology roadmap outlining tailings management methods and research
- Investing almost $2 billion on commercial-scale centrifuge plant; testing of technology exceeds expectations
- Construction continued on $800 million composite tails plant at Aurora Mine
- Regulator notes Syncrude "exceeded expectations" for tailings fines capture over the combined 2010/11 and 2011/12 reporting periods
We recognize stakeholders' interest regarding the pace of reclamation and are vigorously pursuing strategies to accelerate our reduction of fluid fine tailings volumes and their conversion into material that can be used in aquatic, wetland and upland reclamation. In addition, we will continue to share knowledge and actively work with industry partners and the scientific community towards further solutions.
What Are Tailings?
At Syncrude, tailings are a byproduct of our process to extract bitumen from oil sand. Tailings are composed of a mixture of water, sand, clay, fine solids, residual hydrocarbon and salts – all of which are naturally found in oil sands deposits.
Tailings are placed in large landforms commonly referred to as settling basins or tailings ponds. Tailings ponds serve two uses – one, as the recycled water source for our plants and, two, as a containment area which enables tailings to segregate prior to further dewatering for use in reclamation activities.
The primary tailings management challenge is the long period of time it takes for some solid components to settle. While the sand settles rapidly, clay and fine solids (together called fluid fine tailings or FFT) can take decades to settle on their own.
In the settling process, water rises to the top of the tailings pond and is then reused in the bitumen extraction process. Over 85 percent of the water we use is recycled from our settling basins. The Mildred Lake Settling Basin and Aurora Settling Basin are the main sources of recycled water for our operation.
Tailings also contain bitumen that is not recovered in the extraction process. As the bitumen is released, it floats to the top of the settling basin and can appear as an oily slick on the water surface. Bird deterrents are in place year-round to discourage waterfowl from landing (see discussion in Biodiversity chapter).
Bitumen is a valuable natural resource and, while recovery is about 90 percent, we are studying new technologies and processes to increase this even further. This will reduce the amount of bitumen lost to tailings.
Transforming Tailings Into Reclaimed Landscapes
We believe our multi-pronged approach to tailings management will enable us to meet the long-term intent of the Energy Resources and Conservation Board (ERCB) Directive 074. This Directive, established in 2009, specifies performance criteria for the reduction of fluid tailings and the formation of trafficable deposits. Our submission was one of the first to be approved by the ERCB.
As we work towards achieving our plan, three technologies are now being deployed: water capping, composite tails and centrifuging. At the same time, we continue to research additional methods while also participating in Canada's Oil Sands Innovation Alliance (COSIA), which exchanges findings amongst industry operators.
Water capping involves the placement of a layer of water over a deposit of fluid fine tails to form a lake. Syncrude began researching this technology in the 1980s and has demonstrated its viability through laboratory testing and 11 test ponds of various sizes. Results have shown these lakes will evolve into natural ecosystems and, over time, support healthy communities of aquatic plants, animals and fish.
We commissioned the industry's first commercial-scale demonstration of water-capped end pit lake technology in late 2012. It will be used to evaluate the large-scale viability of water capped tailings as a remediation strategy for both fluid fine tailings and oil sands process-affected water. It will be monitored intensively for about 20 years following commissioning to demonstrate that the lake is developing into a viable ecosystem and to prove that this technology can be used on other oil sands leases. Long-term monitoring will continue after this demonstration period is complete.
Composite Tails (CT) combines fluid fine tails with gypsum and sand as tailings are deposited in a mined-out area. This mixture causes the tailings to more quickly settle and release water. CT is then capped with sand and soil, enabling the development of landscapes that support grass, trees and wetlands. This technology is now being used at the Mildred Lake site and will be implemented at the Aurora North Mine starting in 2013 with the construction of a $800 million processing plant.
CT was used in reclamation of our former East Mine. Placement began in 2000 and was complete in 2011. Sand capping to established closure drainage is ongoing. A 54-hectare fen wetland research project has been constructed at the northwest end of this area. Soil and woody debris have been placed and locally-collected seeds spread throughout the area. Close to 100,000 seedlings were planted on the site in 2012. Species include: trembling aspen, white birch, jack pine, white spruce, black spruce, dogwood, green alder and chokecherry. Wetland vegetation will be planted in 2013, at which time active research will begin on hydrology, wetland and terrestrial plant response, and climate conditions. A 65-hectare area directly east of the fen project is expected to be permanently reclaimed in 2015.
Fens are an important type of peat land found in the boreal forest. This large-scale reconstruction effort is the first of its kind in the world and underscores our commitment to return the land we disturb to a condition similar to that prior to disturbance.
We are also working to improve CT deposition and increase fines captured through a technique which places CT under a layer of water or fluid fine tails in the mined-out area. Tailings sand and the fluid fine tails are mixed with gypsum to create CT and, once deposited, water is then released and recycled. Commercial-scale testing is underway.
We have successfully piloted the use of centrifuges to remove the water in fluid fine tails. This technology produces a soft, clay-rich material that can be used as the landform foundation in oil sands reclamation areas. We are implementing this technology in two stages – a commercial-scale demonstration plant which began operations in 2012 and a $1.9 billion full-scale commercial plant to come on-line in 2015. The demonstration plant is performing better than our initial projections – we are currently processing three million cubic metres of fine tailings with plans to expand capabilities to six million in 2014.
The Quest for New Solutions
We are currently researching a number of additional technologies, which could be used to supplement existing remediation methods and reduce bitumen in tailings ponds. These include:
Also referred to as rim ditching, accelerated dewatering is based on methods used in the Florida phosphate industry. It involves depositing fine tailings in a shallow containment structure and removing the water from the surface as it is released. Initial tests have shown a reduction in FFT volume by 50 percent in three to five years. Further study continues on a larger scale.
This method proposes mixing fluid fine tails with overburden, and placing the resulting material into mined-out pit areas for incorporation into reclamation landscapes. A demonstration pilot plant is scheduled to come on-line in 2015.
This method involves placing the clay material from the centrifuge process directly into a former mine pit, rather than in thin lifts, to further dewater. This will reduce the amount of clearing and disturbance otherwise required, while also decreasing transportation distances and related energy use. It could also potentially speed up the time it takes to prepare former mine sites for reclamation activities. A four-year commercial-scale investigation of this method is expected to begin in 2015 in a former mine pit about 50 metres deep.
Bitumen Removal From Tailings Streams
Our extraction process recovers around 90 percent of the bitumen in the oil sand. The remaining bitumen is lost to the tailings stream and enters the settling basin. Recovery of this bitumen represents a significant economic opportunity and addresses key stakeholder and environmental concerns regarding potential risks to waterfowl. Bitumen recovered from either the tailings stream directly or from existing tailings areas would then be processed into crude oil product.
Collaboration Key to Advancements
We work collaboratively with other operators through the Tailings Environmental Priority Area of Canada's Oil Sands Innovation Alliance (COSIA). Through this group, we are sharing the results from our past efforts and cooperating on research and development activities going forward. This initiative foregoes intellectual property rights on technologies and makes $400 million of past industry research available to all parties.
Directive 074 Commitment
As of 2015, Syncrude expects to meet the conditions outlined in the Energy Resources and Conservation Board (ERCB) Directive 074 which requires a minimum 50 percent tailings fines capture. The ERCB approved our plan in 2010, allowing us to construct facilities and implement the proven technologies necessary to ensure full compliance by 2015.
Over the 2010/11 period, we achieved a fines capture of 17.7 percent, almost double our commitment to the regulator. Over the 2011/12 reporting period, due to reliability issues with the composite tails plant, fines capture was lower than the regulated requirements at 8.8 percent. However, over both periods, Syncrude's combined fines capture was around 25 percent more than committed to the regulator.
In total, we are investing significant capital – around $2.8 billion over several years – on meeting the long-term intent of the Directive.