There are thousands of mines around the world producing everything from coal and nickel to diamonds—and they all produce tailings. This includes oil sands mining operations in Alberta.
Managing, and removing oil sands tailings from the landscape is a challenge because it is difficult to remove all the water mixed in during the extraction process.
However, over the last 40 years, leaders from industry, government, the AER, and universities have been working together to shorten the time it takes to restore the land disrupted by tailings waste.
In oil sands mining, tailings are what remain after the oil has been removed from the ore that was scooped out of the ground, plus a lot of water. Tailings include sand, silt, clay, water, and some residual oil.
Tailings are kept in man-made basins called ponds, where they settle. Water is recycled from the ponds, so that less is needed from other sources. That water is constantly recycled and used over and over again.
“Whole tailings” are what is left over when the heavy oil is extracted from the sand.
Over six to eight years, floating solids settle to form “mature fine tailings.” It is on these mature fine tailings that new techniques and technology has focused, leading the way for rapid improvements.
Oil sands mine development, and the tailings that result from it, have a progressive history in Alberta. Over the years, the regulator, industry, and government have worked together to improve tailings management, reduce their environmental footprints, protect people and wildlife, and enhance the land reclamation process.
In the last 10 years, tailings reduction technology has quickly evolved. While there is still work to be done, industry, the AER, and the Government of Alberta have all been implementing changes to accelerate our progress. Here are some key events over the last 20 years that have promoted innovation—and still do.
The Fine Tailings Fundamental Consortium is established to provide scientific understanding of fine tailings. The Government of Alberta and industry get together to share information on fluid tailings and the technologies to treat and reclaim them.
A comprehensive report titled “Advances in Oil Sands Tailings Research” outlining oil sands tailings science and treatment technologies is published by the Government of Alberta.
The report is a culmination of six years of research by the oil sands industry and the Government of Alberta that identifies the technology of adding gypsum to tailings sand and mature fine tailings (MFT) to change MFT from a fluid to a solid. The resulting “clumps” made it easier to separate clay from the water.
Suncor begins using the technology identified in “Advances in Oil Sands Tailings Research” and successfully separates water and clay on a large scale.
Image Credit: Pond 1 photo courtesy of Suncor Energy Inc.
Syncrude starts using the same technology identified in “Advances in Oil Sands Tailings Research” and experiences similar success.
This directive set out new requirements for the regulation of tailings operations associated with mineable oil sands. The directive specified performance criteria for the reduction of fluid tailings.
Suncor applies a technology known as thin-lift evaporative drying, which was developed through laboratory research and field testing, on a large scale. By adding polymer to tailings, the process helps the fine solids and clay particles form together. The mixture is spread across a shallow pond and, once the clumps settle, most of the water can be recycled. Any remaining water evaporates within 21 days.
Image Credit: Courtesy of Shell Canada Limited
Suncor completes its first tailings pond reclamation project, Wapisiw Lookout. Mature fine tailings were removed over 10 years. The pond was filled in with tailings sands, capped with reclamation material, and then trees and grasses were planted on top.
Image Credit: Wapisiw Lookout photo courtesy of Suncor Energy Inc.
Shell tests a type of thin-lift evaporative drying technology at its Muskeg River Mine site.
Syncrude tests a new technology, polymer flocculation. This process aims to remove water from mature fine tailings in a deep pit. A polymer is added to bring the fine solids and clay particles together in clumps. Water is removed through a central sump and a ditch is dug around the pit.
Image Credit: Courtesy of Syncrude Canada Limited
Syncrude tests large-capacity centrifuges to remove water from a polymer and tailings mixture. The dewatered product is trucked to a shallow containment area where it is spread about a metre thick. The remaining water then evaporates.
Image Credit: Courtesy of Shell Canada Limited
About 200 million cubic metres of mature fine tailings are placed in a mined-out pit in Syncrude's base mine area and topped with 5 metres of water to determine whether the lake could reach a reclamation state by natural processes and eventually be connected to the surface water system.
This is a process where mature fine tailings are mixed with dry overburden rich in clay. This helps to absorb the water. Overburden is the material removed from above an oil sands formation and is typically 50 metres thick.
Canadian Natural Resources Ltd. and Imperial Oil start building commercial thickeners expected to be operational between 2016 and 2018. Thickeners are being used commercially for water removal from fluid tailings in other mining operations worldwide.
The Government of Alberta’s new Tailings Management Framework provides direction to the AER and industry on how to manage fluid tailings volumes. It represents an evolution in how industry, the regulator, and the government manage fluid tailings accumulation and risk. It promotes technological innovation, understanding, and certainty around tailings treatment options to ensure fluid tailings volumes are managed into the future.
Want to know more about tailings or other oil sands operations? Be sure to watch Conversations that Matter or check out www.aer.ca for the latest information.
The new tailings directive uses the overall volume of fluid tailings to track reduction. The new requirements are an evolution in how industry, the AER, and government will manage tailings. It tackles existing fluid tailings and new fluid tailings growth. Click here to learn more about Directive 085.