SHELL ALBIAN SANDS OVERVIEW OF TAILINGS AND SHELL TECHONOLOGIES

Transcription

1 SHELL ALBIAN SANDS OVERVIEW OF TAILINGS AND SHELL TECHONOLOGIES

2 WHAT ARE TAILINGS? Oil Sands are a mixture With the bitumen removed, a mixture of bitumen, sand, silt and of water, small amounts of residual clay materials. bitumen, sand, clay particles, small Once excavated, the oil sands go through an extraction process where warm water is added to wash the bitumen off the sand. Once the sand fines particles and other solids are left. The combination is often referred to as tailings, and they can be found across a number of different mining industries. and other particles are removed the bitumen is transported for upgrading and will eventually be used as a source of energy. Illustration showing the flow of the extraction process OIL SANDS EXTRACTION AT SHELL ALBIAN SANDS 1 Tailings can be found across a number of different mining industries. 2

3 WHAT ARE TAILINGS PONDS? WHAT ARE TAILINGS PONDS USED FOR? The pipeline carrying the tailings flow down the dyke walls and into the Once the tailings have reached The water that rises to the top is then runs to a constructed dyke or tailings area. The sand and a lot of the tailings pond a few things recycled back into the plant for the mined out area of the pit which small particles contained in the tailings happen. First, any sand and some of extraction process. The ponds serve an resembles a pond. Once the settles along the dyke walls. Forty to the small clay particles not captured on important purpose as they allow the water tailings are released within the dyke, 50 per cent of the small fines particles the dykes start to settle to the bottom of to be re-used, reducing the need for most of the water and lighter materials are also captured here. the pond and water rises to the top. The fresh water. Shell recycles about rest stay suspended in the water. 80 per cent of the water used in our mining operations % OF THE SMALL PARTICLES ARE CAPTURED ON THE DYKE WALLS Cut-through illustration showing a tailings pond DEPOSIT OF TAILINGS SAND AT SHELL ALBIAN SANDS 3 Sand contained in the tailings settles along the dyke walls. The ponds serve an important purpose as they allow the water to be re-used. 80% OF THE WATER IS RECYCLED Illustration showing the flow of water through the mine 4

4 WHAT HAPPENS ONCE THE TAILINGS HAVE SETTLED? Once all the material in the vegetation, trees and shrubs. The ponds has had time to settle, the quicker the tailings materials settle, process of reclamation begins; the faster these tailings areas can be placing topsoil and then planting transformed into reclaimed land. TAILINGS BEFORE 1 Over time sand, silt, and clay settle to the bottom of the pond. 2 Water is removed for use in the extraction process. TAILINGS AFTER 3 Overburden and top soil are replaced back into the tailing pond. 4 Native vegetation is reintroduced to the site. 5 6

5 WHY ARE PEOPLE CONCERNED ABOUT TAILINGS? WHY ARE TAILINGS PONDS SO BIG? Due to the volume of water, external tailings ponds occupy a fair amount of land. To help reduce the amount of land needed, once mining is sufficiently advanced, tailings are placed in previously excavated areas of the mine. These are called In-Pit tailings. Most operators are now able to use In-Pit tailings areas to reduce their land footprint. At Shell we have one tailings pond for the Muskeg River Mine and one for the Jackpine Mine. BIRD DETERRENT SYSTEMS AT SHELL ALBIAN SANDS Concerns around tailing are focused around the amount of space the ponds take up, the potential threats to wildlife, and the time it takes for the areas to be reclaimed. Tailings are placed in previously excavated areas of the mine. 7 8

6 ARE TAILINGS PONDS A RISK TO WILDLIFE? WHY DOES IT TAKE SO LONG TO RECLAIM A TAILINGS POND? Tailings can contain small amounts of unrecovered bitumen, which sometimes form small patches on the surface of the ponds. The pond s surface area is mostly water just the areas at the edges can be prone to this bitumen. These patches can be a danger to birds and other animals if they try to land on them. Oil sands operators spend millions of dollars on world class wildlife deterrent systems to minimize harm to animals in the area. Our bird deterrent systems have ensured that, very few birds have landed in our tailings ponds. Reducing the amount of these fluid fines has therefore become one of the biggest challenges for the industry accelerating their drying time means we can reclaim the tailings areas faster. The very small fines particles often referred to as Mature Fine Tails or MFT, are not heavy enough to settle to the bottom of the pond, and lie suspended in the water for many years. Because of this we call them fluid fines. Without assistance, these fluid fines would take many years to consolidate. 25 Illustration of bird deterrent system Reclaimed Land 9 10

7 WHAT IS SHELL DOING TO SPEED UP THE PROCESS OF RECLAMATION? WHAT IS BEACHING? Over the last 10 years, Shell Key technologies we are currently When tailings come out of are captured during beaching. At our has spent over $200 million working on include: Beaching, extraction and enter the ponds, Muskeg River Mine, through technology on tailings technology Atmospheric Fines Drying and, most of the sand and a portion application even more of these fines and research. Thickened Tailings. of the fines are captured in the have been captured up to 65 per cent. dykes and beaches. The more fines Shell believes it is very important to captured here, the better; as it reduces continue trying to capture more fines the amount of fines that become fluid. at this stage and stop them from ever Fourty to 50 per cent of these fines becoming fluid. 65% 50% Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ATMOSPHERIC FINES DRYING (AFD) 11 Shell has spent over $200 million on tailings technology and research. A TRUCK DRIVES ON THE SAND CONTAINED IN TAILINGS DYKE. 12

8 WHAT IS ATMOSPHERIC FINES DRYING? Atmospheric Fines Drying or AFD focuses on drying the fluid fines more quickly. 1 A dredge sits in the middle of the tailings pond, and draws the fluid fines out.they are then transported to a drying area. 2 Before they are placed in the drying area, the fines are mixed with a flocculent or thickener, which helps bind them together, into larger particles. 3 This thickened MFT is then spread in thin layers over the drying area. Because the fines are now more tightly bound, the water separates from the fines and drains off the surface. Once the fines have dried completely, further layers are placed on top. This approach results in the fines drying in a matter of weeks, rather than years. 13 This approach results in the fines drying in a matter of weeks. 14

9 WHAT ARE THICKENED TAILINGS? Thickened tailings or TT is currently used exclusively by Shell. After extraction, instead of the tailings going straight to the tailings area, they go to a thickening plant. 1 At the thickening plant, a flocculent or thickener is added to bind the particles together before they reach the tailings pond. 2 The design means a significant amount of the water is drained off at the plant, so that it can be recycled straight back into production. Because the water we drain off is still warm it does not need to be re-heated to the same degree as normal tailings water, when it re-enters production. This means we save energy. 3 Without the water, and with the addition of the flocculent, the tailings are much thicker as they travel to a dedicated disposal area. Here they are again spread in layers, and allowed to consolidate. Because the water we drain off is still warm it does not need to be re-heated to the same degree, therefore saving energy

10 17 All photos taken at Albian Sands, Athabasca Oil Sands Project, Canada 2011

11 PCOEL 08/2012