CA3227878A1 - Method to locate and quantify bitumen mats in oil sands tailings containment ponds - Google Patents

Abstract

The present disclosure relates to locating and quantifying bitumen mats in oil sands tailings ponds utilizing sonar techniques. In surface mined oil sands, bitumen mats can contain bitumen, mineral, emulsified water and trapped gasses in various proportions.
These impurities make sonar detection of the bitumen mats notably different from other oil detection applications. Surprisingly, the composition of the bitumen mats, particularly the gas content, has a significant impact on acoustic waves travelling through the bitumen mats leading to clear distinctions between bitumen mats and MFT mudline. The sonar data can be used to avoid retrieving bitumen mats when fine tailings are supplied from the pond to a flocculation and dewatering operation. The sonar techniques can also be used for locating and quantifying bitumen mats in end pit lakes for optimizing removal of the mats. The sonar techniques allow reduced direct sampling and enhanced detection improving tailings treatment and reclamation.

Description

METHOD TO LOCATE AND QUANTIFY BITUMEN MATS IN OIL SANDS TAILINGS
CONTAINMENT PONDS
TECHNICAL FIELD
[001] The technical field generally relates to identifying bitumen in tailings ponds. In particular, the technical field relates to locating and quantifying bitumen mats in oil sands tailings ponds utilizing sonar techniques.
BACKGROUND

[002] Bitumen mats can accumulate in oil sands tailings ponds and oil sands end pit lakes that contain mature fine tailings (MFT). Accurate location and quantification of bitumen mats can help optimize resource recovery and minimize negative impacts on the reclamation landscape. Recovery of quality tailings from ponds for various tailings treatment technologies could be improved by avoiding bitumen mats during fine tailings recovery. Up to now, inefficient physical sampling has been used to delineate bitumen mats below the water line and at the tailings mudline. An improved technology is needed to help mitigate various drawback of the current techniques.
SUMMARY

[003] The present disclosure relates to locating and quantifying bitumen mats in oil sands tailings ponds utilizing sonar techniques where data can be obtained to map the locations of the bitumen mats. In surface mined oil sands, bitumen mats can contain bitumen, mineral, emulsified water and trapped gasses in various proportions.
These impurities make sonar detection of the bitumen mats notably different from other oil detection applications. It was surprisingly found that the composition of the bitumen mats, particularly the gas content, has a notable impact on the acoustic waves travelling through the bitumen mats. This results in a change in the sonar signal which makes a clear distinction between bitumen mats and the MFT mudline The sonar location data can be used to avoid retrieving bitumen mats when fine tailings are supplied from the pond to a flocculation and dewatering operation. The sonar techniques can also be used for locating and quantifying bitumen mats in end pit lakes and the like for the purpose of optimizing the removal of those mats. The sonar techniques allow reduced direct sampling and enhanced detection that can improve tailings treatment and reclamation.
Date Recue/Date Received 2024-02-01

[004] In some implementations, there is provided a method for identifying bitumen mats in a sub-aerial aquatic storage structure having a water cap and an underlying mineral solids layer divided by a mudline, wherein the bitumen mats are located proximate to the mudline, comprising: transmitting acoustic waves downward through the water cap and the mineral solids layer at a plurality of locations over an area of the sub-aerial aquatic storage structure; receiving acoustic signals corresponding to the acoustic waves and measuring respective time intervals thereof for the respective locations to obtain sonar echo data of the area of the sub-aerial aquatic storage structure; and determining locations of the bitumen mats based on the sonar echo data where sonar measurements show anomalous changes in depth.

[005] In some implementations, the sub-aerial aquatic storage structure comprises a tailings pond. In some implementations, the sub-aerial aquatic storage structure comprises an end pit lake into which treated tailings have been deposited for reclamation.
In some implementations, the transmitting of the acoustic waves and the receiving of the acoustic signals is performed by side-scan sonar. In some implementations, the echoscope is mounted to a boat that displaces over the water cap while transmitting the acoustic waves and receiving the acoustic signals. In some implementations, the method includes determining thicknesses of the bitumen mats based on the sonar data.
In some implementations, determining the locations of the bitumen mats comprises assigning bitumen mat regions where the sonar data indicated a greater depth and/or where the sonar data had weaker signals, compared to regions without a bitumen mat. In some implementations, transmitting acoustic waves is performed over a range of grazing angles between 90 and 30 degrees with an optimal range of 80 to 50 degrees. In some implementations, the acoustic waves that are transmitted have a frequency between 30 kHz and 900 kHz, with an optimum range between 100 and 700 kHz. In some implementations, the acoustic signal that is received to form the sonar echo data comprise first above threshold (FAT) signals. In some implementations, the acoustic signal that is received to form the sonar echo data comprise maximum signals. In some implementations, determining the locations of the bitumen mats comprises assessing backscattering signal differences between bitumen mats and the mudline.

[006] In some implementations, there is provided a process of treating mature fine tailings (MFT) located in a tailings pond, comprising: performing the method as defined Date Recue/Date Received 2024-02-01 above or herein to identify the locations of the bitumen mats; retrieving MFT
from the tailings pond while avoiding or reducing retrieval of the bitumen mats;
subjecting the MFT
retrieved from the tailings pond to a chemical treatment to produce a treated MFT; and discharging the treated MFT into onto a sub-aerial beach for drying; or into a pit to form an end pit lake having a consolidated solids layer below an upper water layer.
In some implementations, the chemical treatment comprises flocculation and the treated MFT
comprises flocculated MFT. In some implementations, the retrieving of the MFT
comprises pumping though a pipeline. In some implementations, the MFT is derived from oil sands processing.

[007] In some implementations, there is provided a process of removing bitumen mats from an end pit lake or other tailings containment area formed by discharging flocculated MFT into a pit to form an upper water layer above a consolidated solids layer, comprising: performing the method as defined above or herein to identify the locations of the bitumen mats located proximate to the consolidated solids layer; deploying a retrieval assembly into the end pit lake such that an inlet thereof is placed at or proximate to the bitumen mats; and operating the retrieval assembly to transport the bitumen mats to surface and thus remove the bitumen mats from the end pit lake. In some implementations, the retrieval assembly comprises a pump and a pipeline. In some implementations, the pump is a submersible pump. In some implementations, the retrieval assembly comprises a boat that displaces on top of the upper water layer.
BRIEF DESCRIPTION OF THE DRAWINGS

[008] The attached figures illustrate various features, aspects and implementations of the technology described herein.

[009] Fig 1 is a process flow diagram showing an example method of identifying bitumen mats.

[0010] Fig 2 illustrates the geometry of an example sonar device with the grazing angles shown for outermost beams.

[0011] Fig 3 shows examples of swaths over bitumen (left) and MFT (right) with the perpendicular distance from the boat to the furthest steady signal indicated.
The color indicates signal strength (red is strongest, green is weakest). In this case there is an Date Recue/Date Received 2024-02-01 almost 10 dB difference in the bitumen signal compared to the MFT signal (10 dB
stronger).

[0012] Fig 4 shows examples of the change in depth estimated from the sonar signal over a bitumen mat (estimated from physical sampling) in white, and the MFT
mudline in grey. There is an approximately 26 cm difference in depth across an average of these transverses.

[0013] Fig 5 is a graph that shows theoretical models for backscattering strength from MFT and a bitumen mat as a function of sonar grazing angle. At the lower grazing angles >80 degrees, the model matches the 10 dB signal difference between a bitumen mat and the MFT mudline suggested in Fig 3.
DETAILED DESCRIPTION

[0014] Techniques described herein relate to methods for locating and quantifying bitumen mats in oil sands tailings ponds or other sub-aerial aquatic storage structures utilizing sonar techniques. It has been found that sonar can be used to leverage a unique property of bitumen mats, notably that bitumen mats include gas bubbles that have an observable impact on sonar such that the bitumen mats can be identified. In this regard, bitumen mats derived from oil sands processing are distinct from other types of hydrocarbons and facilitate detection via sonar techniques. Sonar echo data can be obtained and interpreted to delineate and/or quantify the bitumen mats in fine tailings deposits. Gas content and other properties of bitumen mats affect the sonar echo in ways that allow it to be differentiated from the MFT mudline. The location and extent of the bitumen in the pond can then be quantified by interpretation of the sonar echo data. This approach can then be used to help avoid the bitumen mats being inadvertently supplied into a tailings treatment operation, or alternatively to locate them for specific removal and possible utilization in product streams.

[0015] Referring to Fig 1, the method of identifying bitumen mats can be performed in a tailings pond 10 that includes a water cap 12, an underlying MFT layer 14 below which a coarse solids layer 16 is located. The bitumen mats 18 are present at a mudline 20 defined between the water cap 12 and the MFT layer 14. The method can include implementing a sonar system which is provided at surface, e.g., mounted to a barge or Date Recue/Date Received 2024-02-01 boat, to transmit acoustic waves 24 into the pond 10 and then detecting the sonar echo data 26. The sonar device can be operatively coupled, directly or wirelessly, to a processing unit 23 which can process and interpret the sonar echo data to determine the location of the bitumen mats 18. The processing unit 23 could be located at the oil sands processing facility or proximate the tailings pond 10, and could be programmed based on pre-developed models to display or otherwise provide information regarding the bitumen mats based on the sonar echo data.

[0016] Fig 1 also shows that MFT 14 can be retrieved from the pond 10, combined with a flocculant 28 (e.g., polymer flocculant) and optionally additional chemicals, and then the resulting flocculated MFT 30 can be discharged into a pit to form an end pit lake 32 that has an upper water layer 34 and a lower consolidated solids layer 36. The retrieval of the MFT can be adjusted such that the bitumen mats 18 are avoided, as the bitumen mats can interfere with flocculation and overall tailings treatment and reclamation. It is also noted that a coagulant can be added to the MFT before, during or after addition of the flocculant.

[0017] In this regard, there are various tailings treatment processes that include centrifuging as well as flocculation and dewatering processes that can be used to separate water from MFT. The presence of bitumen mats in MFT retrieved from the pond can negatively interfere with such tailings treatment processes. By identifying the locations and optionally quantifying the bitumen mats in the tailings pond, the bitumen mats can be avoided when the MFT is pumped out of the pond for treatment. Example fine tailings treatment methods and systems are described in Canadian patent documents CA 2,958,873; 2,921,835; 2,701,317; 2,820,259; 2,820,324; 2,820,660;
2,820,252;
2,820,267; 2,772,053; 2,705,055; 3,080,336; 3,062,152; 2,975,145; 2,932,079;
2,909,388;
2,908,086; and 2,886,983, although it is noted that various other processes could also be used for treating tailings in conjunction with the bitumen mat detection methods described herein.

[0018] It is also noted that the method of identifying bitumen mats can be used in other aquatic storage structures, such as the end pit lake, to identify any bitumen mats to facilitate removal of the bitumen mats. In end pit lakes, bitumen mats could be present at the interface between the upper water layer 34 and a lower consolidated solids layer 36.
Date Recue/Date Received 2024-02-01

[0019] The echolocation techniques for identifying bitumen mats can replace physical sampling or could be combined with physical sampling or other detection techniques.
Avoiding or reducing physical sampling could result in various advantages and accurate delineation of bitumen mats can also facilitate improved performance of tailings treatment and reclamation processes.

[0020] Potential implementations of the methods were tested in a tailings pond using a CodaOctopusTM Echoscope and showed variations in the signal strength and measured depth that corresponded with the estimated location of bitumen mats as determined from direct physical sampling. Over the bitumen mats, the measured sonar signal was less intense and measured a greater depth than where no bitumen mat was expected.
The difference in the signal can be explained by modelling the bitumen mat as resting on top of the mudline, and assuming little backscattering of sound waves occurs at the top of the bitumen mat. The surprizing increase in measured depth can be explained by gas bubbles in the bitumen mats which decrease the speed of sound in the bitumen mats. The presence of gas bubbles in oil sands bitumen mats makes sonar detection a viable alternative to physical sampling at least in part due to the unique impact the gas bubbles have on the sonar signal.

[0021] The additional depth measured from the sonar signal can be combined with properties of the bitumen mat (in terms of bitumen, water, solids) to estimate the gas content in the bitumen mat. Where there was no bitumen, the sonar signal was due to backscattering from the water-mature fine tailings (M FT) mudline. By fitting the water-M FT
data to a standard sediment backscattering model, an estimate for the backscattering intensity from the bitumen-MFT interface can be obtained using the estimated composition of the bitumen mat. This model for the sonar signal from the bitumen mat was a good approximation of the measured signal and might be complemented with additional data gathered using different settings in the sonar detection system. Table 2 shows the relationship between gas content and speed of sound in a hypothetical bitumen mat with 82% bitumen, 15% water, and 3% solids. Identification of the bitumen mat location does not depend on any physical sampling and associated data, but accurate estimates of the bitumen mat volume would require information about the bitumen mat composition (bitumen, water, and solids).
Date Recue/Date Received 2024-02-01

[0022] In this instance, a CodaOctopusTM Echoscope was used to create sonar images of the mudline in a corner of a tailings pond. The echoscope was angled at 77 below the horizontal and took images of a 52 x52 area using a 128x128 grid of beams, corresponding to roughly a 10.4m by 9.8m area of the MFT mudline. The geometry of the echoscope alignment is shown in Fig 2; the distances are calculated assuming a constant water cap depth of 10m. With this setup, the lowest measured grazing angle perpendicular to the boat was 51 . Although Fig 2 shows that the CodaOctopusTM is collecting data from a wide area, not all are required, e.g., only the signal perpendicular to the boat could be collected. This means that any side scan sonar equipment could be used to identify the location of bitumen mats.

[0023] In this example, the sonar imaging was done using the first above threshold (FAT) signal, with a threshold set at 45dB for some of the images and at 43dB
for others.
The depth measured by the sonar appears to corelate with the location of the bitumen mats. In addition to seeing an increased depth over the bitumen mats, the overall signal is weaker and beyond a certain distance from the boat (i.e. below a certain grazing angle) virtually no signal is above the threshold. Fig 3 shows the difference in the sonar measurements over bitumen (left) and over MFT (right), along with the estimated distance from the boat that the signal extends in each case. In principle, any sonar signal system investigating the location of the mudline could be used to identify the location of bitumen mats using changes in the sonar reflections due to the presence of bitumen mats.

[0024] In addition to the difference in signal intensity shown in Fig 3, there is also a difference in the measured distance to the MFT mudline, where the measured distance is greater over the bitumen mats than it is over the MFT. The difference in sonar signal intensity is due to properties of the bitumen mat.

[0025] The decrease in signal intensity over the bitumen mat compared to MFT is shown in Fig 3. The echoscope measured a difference in peak signal strength of roughly dB, similar to that estimated from the modelled sonar signal intensity in Fig 5. Sonar is primarily used to measure distances or depth, in this case the distance to the mudline.
Fig 4 shows that the echoscope measurements of the depth of the lake are different over where bitumen mats are known to be based on physical sampling. Averaging measurements from several locations gives a depth of roughly 9.94 m over MFT
and a Date Recue/Date Received 2024-02-01 depth of roughly 10.2 m over bitumen mats. This is an additional 26 cm of depth measured over the bitumen mat than over the MFT.

[0026] The bitumen mats are known to rest at the mudline; therefore, for the sonar system to measure a greater distance to the bitumen mat than there actually is, the sound waves must be passing through the bitumen mats and reflecting mainly off the MFT below.
Some studies of the use of sonar to detect oil spills in the ocean have suggested that crude oil is mostly transparent to sound waves which would imply similar difficulties in detecting bitumen accumulations as for conventional oil spills. In surface mined oilsands, bitumen mats can contain bitumen, mineral, emulsified water and trapped gasses in various proportions. These impurities make sonar detection of the bitumen mats significantly different from other oil detection applications. When the sound waves pass through the bitumen mat the gas content reduces the speed of sound which causes a refraction effect the makes the bitumen mat area to appear deeper than the surrounding MFT. This is exactly the effect observed and discussed previously.

[0027] If the bitumen mat is resting on the mudline, the additional depth measured can be determined as follows:
c, Ad = h¨cb ¨ h

[0028] Here, h is the thickness (height) of the mat, and c and cb are the speed of sound in water and the bitumen mat respectively. Since the thickness of the bitumen mats is expected to be much less than the roughly 26 cm of extra depth measured, the speed of sound in the bitumen mat must be less than the speed of sound in water to explain the extra depth measured. The thickness of the bitumen mat will depend on the gas and solids content, but can be estimated to be between 2 and 5 cm depending on the volume of gas.

[0029] Four possible components for the bitumen mat are considered, bitumen, water, solids and gas bubbles. To determine the properties of the bitumen mat, as well as the properties of the MFT sediment, the density and either the speed of sound or the bulk modulus of each component could be used. Although there are likely several different materials contributing to the solids and gas contents, for simplicity they will be modeled as a single component each. The values used in this model are summarized in Table 1.
Date Recue/Date Received 2024-02-01 Table 1: Properties of the individual components of the bitumen mats Component Density (kg/m3) Speed of Sound Bulk Modulus (m/s) (GPa) Bitumen 1010 1720 2.988 Water 1000 1430 2.045 Solids 2650 2800 20.776 Gas 2.292 331 0.000251

[0030] These values are used to estimate the speed of sound and density of both the bitumen mats and the MFT. The bulk modulus of a solid or fluid suspended in a liquid can be calculated from the bulk moduli of the components as follows:

Km = _________________________________________ Vm Ks

[0031] Here, K and V are the bulk moduli and volumes respectively and the subscripts indicate the suspension (s), the liquid (I), or the overall mixture (m). The MFT is assumed to be 30% solids by mass and have no significant amounts of bitumen or gas.
This leads to a density of 1230 kg/m3, and a speed of sound of 1379 m/s in the MFT.

[0032] Sampling of the bitumen mats has shown that they have a wide range of bitumen, water, and solids content. Since the amount of gas in the bitumen mats cannot be easily measured by direct sampling it will have to be estimated based on the expected speed of sound and mat thickness required to account for the sonar measurements. With no gas present, the mat composition leads to a speed of sound higher than in water which does not agree with the sonar data. There must be enough gas present to significantly reduce the speed of sound, but the overall density of the bitumen mat must remain greater than the density of water. The relevant properties of bitumen mats with different amounts of gas bubbles are summarized in Table 2. The data in Table 2 was created assuming a hypothetical bitumen mat with 82% bitumen, 15% water, and 3% solids.
Table 2: Properties of bitumen mats with different volumes of gas bubbles Volume of Gas Speed of Density Mat Thickness Extra (%) Sound (m/s) (kg/m3) (cm) Measured Depth (cm) 0.0 1656 1029 1.7 0.0 1.0 156.3 1018 2.1 17.1 1.5 128.2 1013 2.4 25.1 Date Recue/Date Received 2024-02-01 2.0 111.4 1008 3.2 37.4 2.5 99.9 1003 5.2 68.7

[0033] As a starting point the bitumen mat can be modelled assuming there is 2% gas by volume along with the bitumen, water and solids content given from sampling. The model can be refined with additional sonar data or sampling measurements. The acoustic properties for the water, bitumen mats, and MFT are summarized in Table 3.
Table 3: Acoustic Properties of materials in surface mined oilsands Speed of Sound Density (kg/m3) Acoustic (m/s) Impedance (kg/m2/5 x106) Water 1430 1000 1.43 Bitumen Mats 111.4 1008 0.11 MFT 1379 1230 1.70

[0034] The theoretical model for sediment backscattering provides estimates for the backscattering strength from the MFT mudline based on its composition. Since the depth data suggests that the received signal passes through the bitumen mat, the signal can be modelled in two parts. The first part is the effect of the bitumen mat on the signal, and the second part uses the model parameters obtained to estimate the backscattering from a bitumen-MFT interface.

[0035] The modelling of the backscatter strength shown in Fig 5 suggests that scattering where there is no bitumen will be above the threshold for all angles measured by the echoscope (out to 8.1 m), while the signal over bitumen will be below the threshold at a grazing angle of roughly 58 (out to 6.2 m). This is reasonably close to the 6.9 m for MFT and 5.6 m for bitumen mats estimated from the sonar images (Fig 3).

[0036] In summary, sonar measurements of a surface mined tailings pond using the showed differences in the measured depth and intensity of the return signal that roughly correspond with the estimated locations of bitumen mats as determined by direct sampling. While the CodaOctopusTM echoscope data used in the examples provides real-time sonar imaging over an extended area, this is not necessary to map the locations of bitumen mats with sonar. Any side scan sonar device can collect data that can be used to determine the locations of bitumen mats. The direct sampling is time consuming and does Date Recue/Date Received 2024-02-01 not provide a highly accurate or high-resolution picture of the bitumen mats, and thus an alternative method for locating the bitumen mats is desirable.

[0037] Surprisingly, the estimated depth of the pond mudline from the sonar signal is significantly lower when over a bitumen mat. This implies that sonar signals can be used to locate bitumen mats in surface mined oilsands tailings containment. As noted, this depth difference can be explained by the presence of gas bubbles in the bitumen mats which is unique to surface mined oilsands tailings.

[0038] Using the estimated composition of the bitumen mat along with the theoretical model for backscattering from the MFT mudline, the strength of a sonar signal that has travelled through the bitumen mat and backscattered off the MFT can be estimated. This theoretical model accounts for both the extra depth measured by the sonar over bitumen mats, and the decreased signal strength. The agreement between the models and the measured signal demonstrates that the measured signal travels through the bitumen mat and returns from the MFT below. Since the sonar signals are travelling through the bitumen mats, the thickness and composition of the mats can be estimated from the sonar signals.

[0039] Several alternative implementations and examples have been described and illustrated herein. The implementations of the technology described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual implementations, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the implementations could be provided in any combination with the other implementations disclosed herein. It is understood that the technology may be embodied in other specific forms without departing from the central characteristics thereof. The present implementations and examples, therefore, are to be considered in all respects as illustrative and not restrictive, and the technology is not to be limited to the details given herein. Accordingly, while the specific implementations have been illustrated and described, numerous modifications come to mind.
Date Recue/Date Received 2024-02-01

Claims (20)

12

1. A method for identifying bitumen mats in a sub-aerial aquatic storage structure having a water cap and an underlying mineral solids layer divided by a mudline, wherein the bitumen mats are located proximate to the mudline, comprising:
transmitting acoustic waves downward through the water cap and the mineral solids layer at a plurality of locations over an area of the sub-aerial aquatic storage structure;
receiving acoustic signals corresponding to the acoustic waves and measuring respective time intervals thereof for the respective locations to obtain sonar echo data of the area of the sub-aerial aquatic storage structure; and determining locations of the bitumen mats based on the sonar echo data where sonar measurements show anomalous changes in depth.

2. The method of claim 1, wherein the sub-aerial aquatic storage structure comprises a tailings pond.

3. The method of claim 1 or 2, wherein the sub-aerial aquatic storage structure comprises an end pit lake into which treated tailings have been deposited for reclamation.

4. The method of any one of claims 1 to 3, wherein the transmitting of the acoustic waves and the receiving of the acoustic signals is performed by side-scan sonar.

5. The method of claim 4, wherein the echoscope is mounted to a boat that displaces over the water cap while transmitting the acoustic waves and receiving the acoustic signals.

6. The method of any one of claims 1 to 5, further comprising determining thicknesses of the bitumen mats based on the sonar data.

7. The method of any one of claims 1 to 6, wherein determining the locations of the bitumen mats comprises assigning bitumen mat regions where the sonar data indicated a greater depth and/or where the sonar data had weaker signals, compared to regions without a bitumen mat.

8. The method of any one of claims 1 to 7, wherein transmitting acoustic waves is performed over a range of grazing angles between 90 and 30 degrees with an optimal range of 80 to 50 degrees.

9. The method of any one of claims 1 to 8, wherein the acoustic waves that are transmitted have a frequency between 30 kHz and 900 kHz, with an optimum range between 100 and 700 kHz.

10. The method of any one of claims 1 to 9, wherein the acoustic signal that is received to form the sonar echo data comprise first above threshold (FAT) signals.

11. The method of any one of claims 1 to 10, wherein the acoustic signal that is received to form the sonar echo data comprise maximum signals.

12. The method of any one of claims 1 to 11, wherein determining the locations of the bitumen mats comprises assessing backscattering signal differences between bitumen mats and the mudline.

13. A process of treating mature fine tailings (MFT) located in a tailings pond, comprising:
performing the method as defined in any one of claims 1 to 12 to identify the locations of the bitumen mats;
retrieving MFT from the tailings pond while avoiding or reducing retrieval of the bitumen mats;
subjecting the MFT retrieved from the tailings pond to a chemical treatment to produce a treated MFT; and discharging the treated M FT
into onto a sub-aerial beach for drying; or into a pit to form an end pit lake having a consolidated solids layer below an upper water layer.

14. The process of claim 13, wherein the chemical treatment comprises flocculation and the treated MFT comprises flocculated M FT.

15. The process of claim 13 or 14, wherein the retrieving of the MFT comprises pumping though a pipeline.

16. The process of any one of claims 13 to 15, wherein the MFT is derived from oil sands processing.

17. A process of removing bitumen mats from an end pit lake or other tailings containment area formed by discharging flocculated MFT into a pit to form an upper water layer above a consolidated solids layer, comprising:
performing the method as defined in any one of claims 1 to 12 to identify the locations of the bitumen mats located proximate to the consolidated solids layer;
deploying a retrieval assembly into the end pit lake such that an inlet thereof is placed at or proximate to the bitumen mats; and operating the retrieval assembly to transport the bitumen mats to surface and thus remove the bitumen mats from the end pit lake.

18. The process of claim 17, wherein the retrieval assembly comprises a pump and a pipeline.

19. The process of 18, wherein the pump is a submersible pump.

20. The process of any one of claims 17 to 19, wherein the retrieval assembly comprises a boat that displaces on top of the upper water layer.