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Y. Yao
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Dewatering Behaviour of Fine Oil Sands Tailings
An Experimental Study
Doctoral thesis
(2016)
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Yutian Yao
Oil sands tailings are a warm aqueous suspension of sand, silt, clay, residual bitumen and naphtha. The tailings are hydraulically transported and stored in tailing ponds where they segregate, with the sand settling from suspension forming beaches and the remaining tailings flowing to the middle of the pond. After several years of tailings disposal, three layers have developed in the pond, which are, from top to bottom, water, thin fine tailing and mature fine tailing (MFT). MFT is the major reason that the tailing ponds cannot be reclaimed. Due to low the high water content and low hydraulic conductivity, MFT consolidate very slowly in the ponds. Therefore, many technologies have been proposed remove the water from the tailings and increase the consistency so that the tailing pond can be reclaimed. but most of these dewatering technologies are rejected due to the limited technical or economic feasibility. In this PhD thesis, two potential fine tailings management technologies were described. These two technologies were: (1) sub-aerial drying of fine tailings deposited in thin lifts, and (2) use of prefabricated vertical drains (PVD) in enhancement of consolidation of fine tailings in the pond. In this PhD project, experiments were carried out to investigate geotechnical properties and dewatering behaviour of fine oil sands tailings related to the described technologies.
...
Oil sands tailings are a warm aqueous suspension of sand, silt, clay, residual bitumen and naphtha. The tailings are hydraulically transported and stored in tailing ponds where they segregate, with the sand settling from suspension forming beaches and the remaining tailings flowing to the middle of the pond. After several years of tailings disposal, three layers have developed in the pond, which are, from top to bottom, water, thin fine tailing and mature fine tailing (MFT). MFT is the major reason that the tailing ponds cannot be reclaimed. Due to low the high water content and low hydraulic conductivity, MFT consolidate very slowly in the ponds. Therefore, many technologies have been proposed remove the water from the tailings and increase the consistency so that the tailing pond can be reclaimed. but most of these dewatering technologies are rejected due to the limited technical or economic feasibility. In this PhD thesis, two potential fine tailings management technologies were described. These two technologies were: (1) sub-aerial drying of fine tailings deposited in thin lifts, and (2) use of prefabricated vertical drains (PVD) in enhancement of consolidation of fine tailings in the pond. In this PhD project, experiments were carried out to investigate geotechnical properties and dewatering behaviour of fine oil sands tailings related to the described technologies.
Dewatering behavior of fine oil sands tailings
A summary of laboratory results
To evaluate the disposal technology for fine oil sands tailings, the appropriate engineering properties of the tailings should be ascertained. A laboratory study was conducted by Delft University of Technology (the Netherlands) on the geotechnical properties and dewatering behavior of the fine oil sands tailings (MFT, TT), obtained from Shell Canada’s Muskeg River Mine. In this program, the tailings were characterized by performing various laboratory tests including index property tests, flocculation tests, column settling tests, oedometer tests, shrinkage and swelling tests, water retention tests, cracking tests and air drying tests. In this paper, a summary of the main tests results is presented. The data obtained for the MFT and flocculated MFT are compared to identify the effects of flocculation on the dewatering behavior.
...
To evaluate the disposal technology for fine oil sands tailings, the appropriate engineering properties of the tailings should be ascertained. A laboratory study was conducted by Delft University of Technology (the Netherlands) on the geotechnical properties and dewatering behavior of the fine oil sands tailings (MFT, TT), obtained from Shell Canada’s Muskeg River Mine. In this program, the tailings were characterized by performing various laboratory tests including index property tests, flocculation tests, column settling tests, oedometer tests, shrinkage and swelling tests, water retention tests, cracking tests and air drying tests. In this paper, a summary of the main tests results is presented. The data obtained for the MFT and flocculated MFT are compared to identify the effects of flocculation on the dewatering behavior.
Consolidation and atmospheric drying of fine oil sand tailings
Comparison of blind simulations and field scale results
This paper presents a comparison between blind predictions of field tests of atmospheric drying of mature fine tailings (MFT) presented in IOSTC 2014 and field results. The numerical simulation of the consolidation and atmospheric drying of selfweight consolidating fine material is challenging and requires significant knowledge of the material, climate and the interaction between the two. This paper presents the outcome of a study which developed a numerical model, undertook material characterization and predicted the behaviour of full scale field tests undertaken in Shell Canada’s Muskeg River Mine near Fort McMurray, Alberta. The blind predictions were published in IOSTC 2014. A comparison between the observed and simulated behaviour in terms of settlement and void ratio yields a number of conclusions regarding the model: (i) all of the major observed features can be predicted by the numerical model; (ii) the quantification of the behaviour is well represented; (iii) due to the fast initial consolidation, the amount of material recorded as being deposited was underestimated; (iv) significant shear strength development requires a void ratio reduction which either requires a significant overburden or atmospheric drying.
...
This paper presents a comparison between blind predictions of field tests of atmospheric drying of mature fine tailings (MFT) presented in IOSTC 2014 and field results. The numerical simulation of the consolidation and atmospheric drying of selfweight consolidating fine material is challenging and requires significant knowledge of the material, climate and the interaction between the two. This paper presents the outcome of a study which developed a numerical model, undertook material characterization and predicted the behaviour of full scale field tests undertaken in Shell Canada’s Muskeg River Mine near Fort McMurray, Alberta. The blind predictions were published in IOSTC 2014. A comparison between the observed and simulated behaviour in terms of settlement and void ratio yields a number of conclusions regarding the model: (i) all of the major observed features can be predicted by the numerical model; (ii) the quantification of the behaviour is well represented; (iii) due to the fast initial consolidation, the amount of material recorded as being deposited was underestimated; (iv) significant shear strength development requires a void ratio reduction which either requires a significant overburden or atmospheric drying.