Geotechnical Performance of ATA -Treated Fluid Fine Tailings

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1 Geotechnical Performance of ATA -Treated Fluid Fine Tailings T. Moore, Thurber Engineering Ltd., Canada C. Zhang, Thurber Engineering Ltd., Canada M. Pinheiro, Thurber Engineering Ltd., Canada

2 Outline Background CT Technology ATA TM Technology Laboratory Testing Material Description Consolidation Response Comparative Analysis Consolidation Behaviour

3 Background Focus: Oil Sands Tailings Challenges Reclamation of fluid fine tailings ( a uniquely Canadian issue ) Requires large containment areas Requires long-term storage to enable settling and water release Is impaired by poor drainage and strength properties Directive 074: 5 kpa undrained shear strength 1 year after deposition 10 kpa undrained shear strength 5 years after deposition

4 Background Fine Fluid Tailings How to tackle the problem from a geotechnical engineering standpoint? Terzaghi s 1D Consolidation Theory Rate of Consolidation Consol. Coefficient Hydraulic Conductivity Time Factor Drainage Path Compressibility

5 Background Tailings Treatment Technologies Oil Sands Tailings Technology Deployment Roadmap reports 500+ tailings treatment technologies Our focus today: Composite Tailings ATA TM

6 CT Technology sand coagulated fines NST or CT Mixture Composite Tailings (CT) Coarse and fine tailings streams are mixed in and a chemical amendment added to the mix to produce a non-segregating tailings. The coarse tailings stream is typically a sand slurry. The fines tailings stream can be sourced as: Mature fine tailings (MFT) Composite tailings Thickened tailings (TT) Non-segregating tailings Chemical amendment: Gypsum, lime, CO2

ATA TM Technology ATA Tailings Three-component system: Activator polymer Tether polymer Anchor particles Process: When the loosely aggregated

7 ATA TM Technology ATA Tailings Three-component system: Activator polymer Tether polymer Anchor particles Process: When the loosely aggregated and activated clays are combined with the tethered sand particles, they quickly bind to each other to form larger solid clusters, which are then readily dewatered. The strong forces generated by the chemical interaction between activator and tether surfaces are the cornerstone of this technology. activator polymer added to the fines stream tether polymer added to the coarse stream treated streams mixed in fines bound to sand water

8 NST SFR = 4 Solids = 65.7% Yield strength = ~30 Pa ATA SFR = 4 Solids = 63.7% Yield strength = ~1000 Pa

9 Laboratory Program Objective: Establish geotechnical behavioural relationships needed for numerical analyses and feasibility assessment. Components: Material characterization (Atterberg limits, specific gravity, particle size distribution curves, MBI, etc.) Consolidation behaviour (large-strain consolidation, hydraulic conductivity and consolidated undrained triaxial compression tests)

10 Laboratory Testing Material Description (ATA-amended tailings) Testing conducted on tailings samples at different sands-to-fine ratio (SFR) values. SFR = 1 SFR = 2 SFR = 4 SC [%] solids content (by weight) b [%] bitumen/solids (by weight) f [%] fines/solids (f < 44 μm) s [%] sand/solids (s > 44 μm) c [%] clay fraction (< 2 μm) (dispersed)

11 Laboratory Testing Consolidation Behaviour Consolidometer cell developed inhouse (Moore et al., 2013) Vertical effective stress vs. void ratio (compressibility) Hydraulic conductivity vs. void ratio consolidometer cell

12 Compressibility Response

13 Hydr. Conductivity vs. Void Ratio 2 orders of magnitude

14 Hydr. Conductivity vs. Fines Void Ratio

15 Consolidation Analysis Objective: Compare the long-term consolidation performance of the ATA-treated tailings with SFR = 2.0 and CT with similar SFR. Filling Scenario Total deposit wet thickness = 40 m Filling rate = 5 m/year Filling period = 8 years. 5 m 5 m 5 m 5 m Modelling Framework and Assumptions 5 m 1D finite strain consolidation 5 m Upper drainage only (no under-drainage) 5 m No evaporation or freeze-thaw 5 m

16 Results Deposit thickness vs. time and excess porewater pressure End 10 5 of Years Deposition After End of Deposition 19% 100% 93%

17 Conclusion The compressibility of the ATA-treated tailings (at an SFR = 2) is somewhat similar to that of a CT tailings with similar SFR. However, its hydraulic conductivity is about 100-fold higher than that of the CT. As a consequence, the ATA-treated tailings (at an SFR = 2) showed much better consolidation performance than the CT tailings with similar SFR. Other positive implications can be drawn from these results: Higher net water release More efficient heat recovery No reworking of solids after deposition

18 Acknowledgments Soane Energy LLC Teck Resources Ltd. Thurber Engineering Ltd. All individuals involved in the careful execution of the laboratory tests.

Effect of various treatments on consolidation of oil sands fluid fine tailings

Effect of various treatments on consolidation of oil sands fluid fine tailings Louis K. Kabwe, G. Ward Wilson, J. Don Scott, Amarebh Sorta & Nicholas A. Beier Department of Civil and Environmental Engineering