Alberta Energy

Tailings reclamation is a significant challenge facing the oil sands industry. There are 1.4 billion m 3 of fluid fine tailings (FFT), a slurry waste stream generated from oil sands surface mining, awaiting reclamation. Pit lakes may be a suitable reclamation option, however further evaluation is required before pit lakes receive regulatory approval as an FFT reclamation method. FFT destined for pit lakes may be treated (with alum and polyacrylamide) and contain residual hydrocarbons. This study is the first publicly available comparison of the behavior of untreated versus treated FFT in pit lakes. Forty columns were monitored for 540 d under anaerobic conditions to evaluate the effects of tailings treatment, hydrocarbon amendments, and temperature (10 °C and 20 °C) on the biogeochemical and geotechnical behavior of FFT in pit lakes. Although tailings treatment aims to improve dewatering performance, this study found that treatment significantly reduced dewatering and consolidation. This highlights challenges in achieving optimal flocculation conditions, even in a controlled laboratory setting. Tailings treatment and hydrocarbon amendments significantly enhanced sulfate reduction, which was the dominant microbial process. Treated FFT had a greater abundance of known sulfate reducing bacteria and more extensive sulfate reduction than untreated FFT, while hydrocarbon amendments quickly led to >99% sulfate reduction. Sulfate reduction generated dissolved sulfide species throughout the columns and led to significant increases in alkalinity and CO 2(g) . Divalent cations were subsequently impacted and presumably precipitated as carbonate minerals. These pore water chemistry changes resulted in higher tailings solids contents, leading the authors to propose a new bioconsolidation pathway for FFT via sulfate reduction. • Coagulation/flocculation treatment decreased tailings dewatering and consolidation • Sulfate reduction was significantly enhanced by tailings treatment and hydrocarbons • Treated tailings had a greater abundance of sulfate reducing bacteria • Hydrocarbon amendments led to rapid and > 99% sulfate reduction • Sulfate reduction increased alkalinity and CO 2 and decreased cation concentrations

Abstract This paper presents results from novel tests investigating screen plugging and the factors that influence it. The study focuses on sand retention and flow convergence into screens, assuming formation collapse. Controlled experiments were conducted to evaluate the performance of different screens and the role of sand in plugging. The tests also explore how drilling and completion processes affect screen performance and plugging behavior. A novel test procedure was developed to simulate sand retention on screens. Screens with retained sand were placed in a flow apparatus to study multiphase flow behavior. A mix of sand and fines slurry was used to evaluate screen and near-screen plugging. The effect of mud and filter cake was assessed by allowing cake formation on the sand face before flowing. Additionally, the influence of temperature—up to 200°C—was examined to understand thermal impacts on screen plugging mechanisms under realistic downhole conditions. This study utilized three Particle Size Distribution (PSD) classes from the McMurray Formation to represent common variations in thermal project sands. A common polymeric mud, representative of the mud system used in thermal drilling, was employed. The thickness of the mud cake varied significantly among the three sands and was directly related to their permeability, with finer sands forming denser cakes that reduced retained permeability by over 55% in the lowest permeability class. Experiments during the drawdown phase revealed that wire-wrapped screens outperformed punch screens in permeability recovery due to enhanced channeling, with coarser PSDs showing better restoration (up to 72% retention). Thermal exposure at 200°C, intended to break down polymers, instead densified the cake with residue deposition, reducing post-steaming permeability by 5-30% depending on PSD, though wire-wrapped screens with 100-150 μm slots mitigated losses. Plugging occurred primarily at the sand-cake interface, emphasizing the need for near-screen management. These findings support preventive measures to minimize plugging and optimize thermal performance. This study aims to help engineers understand the key factors influencing screen plugging and the resulting high differential pressure drop between injectors and producers. The insights gained support the implementation of preventive measures to avoid or minimize screen plugging, improving overall system performance and reliability.

ABSTRACT As high latitudes warm, there is limited knowledge of how rapidly changing species composition and density, combined with shifting precipitation and thawing permafrost, will affect critical zone water fluxes across the subarctic. Here, we use stable isotopes of hydrogen and oxygen to assess the role of soil moisture, precipitation dynamics and plant species on the timing, magnitude and sources of plant water uptake at three sites along an elevational gradient in a subarctic, alpine catchment in southern Yukon, Canada. The sites ranged from a low‐elevation boreal forest to higher elevation shrub taiga with variable shrub cover. We sampled soil and xylem water approximately every 3 weeks from pre‐leaf out to post‐senescence over two hydrologically distinct years. We answer the questions: (1) What are the seasonal and interannual changes in the isotopic composition of soil and xylem water across this range of subarctic vegetation covers?, (2) How does the seasonal origin of xylem water vary in wet and dry conditions? and (3) Do different shrub species at the same location rely on different sources of water? Results showed that while δ 2 H and δ 18 O of volume weighted precipitation became more negative with elevation, the opposite was true of xylem water. Despite less snowfall at lower elevations, plant water uptake was more reflective of snow water at the forest than at the high elevation shrub sites. Near‐surface bulk soil water had lower line‐conditioned excess at the forest than at the shrub sites throughout the season and with depth, highlighting increased contributions from soil evaporation at the forest. Differences in annual precipitation and climate had a strong influence on stable isotopes of hydrogen and oxygen in the soil. These results demonstrate that vegetation type and elevation strongly mediate plant water sourcing and evaporative partitioning in subarctic catchments, underscoring the need to account for species‐specific and landscape‐scale variability when predicting blue/green water fluxes in a changing climate.

This paper investigates how people use physical space, free from digital constraints, to organize thoughts and ideas. Such spatial arrangements commonly support sensemaking, idea generation, and data understanding. We collected over 300 publicly shared images capturing these activities collected from real-world contexts. Our visual analysis identifies a small set of recurring spatial patterns such as clusters, grids as well as the techniques people use to build and adapt them, such as color coding, directional lines, and selective rule-following. We discuss how these practices can inform the design of more expressive and adaptable digital spatially-aware tools that better support the diverse ways people think with space.

Landfill gas (LFG) models traditionally assume homogeneous waste degradation using a single set of parameters—such as the first-order rate constant (k) and methane potential (L0)—to predict methane (CH4) generation. However, this study demonstrates that waste degradation is highly heterogeneous, with significant spatial variability in CH4 generation and oxidation potential. We investigated the biochemical methane potential (BMP) and methane oxidation potential (MOP) of excavated waste residue (EWR) from different depths within the Calgary Biocell, a landfill bioreactor operated for 14 years with leachate recirculation. Using a modified BMP assay, 12 batch experiments—including 3 composite replicates, 8 grab samples, and 1 blank—were conducted. Results revealed that deeper regions of the Biocell exhibited greater waste degradation, with EWR samples from these zones showing an average L0 of 8.28 mL CH4/g TS, significantly lower than the 18.21 mL CH4/g TS observed in shallower regions. Additionally, EWR samples with higher proportions of paper and cardboard produced greater methane potential. Methane oxidation potential was also depth-dependent, with EWR from deeper regions showing a 62% higher maximum CH4 oxidation rate (Vmax = 0.76 μmol/h) compared to shallower regions (Vmax = 0.47 μmol/h/g). These findings challenge the assumption of homogeneous waste degradation in landfills and highlight the need for spatially resolved models to accurately predict CH4 generation and recovery. The study also underscores the potential for valorizing EWR in landfill biocovers and other sustainable waste management applications.

<strong class="journal-contentHeaderColor">Abstract.</strong> Karst springs in alpine catchments are important for maintaining groundwater-dependent ecosystems in fragile environments and for sustaining baseflow in mountain rivers. Despite its importance, rugged and inaccessible terrains pose major challenges in hydrogeological studies of alpine karst. This study developed a practical approach for characterizing an alpine karst system in the Canadian Rocky Mountains that had no previous information aside from the location of the spring outlet. Using geological maps, satellite images, simple water balance, water sampling and analysis, and dye tracer tests, it was possible to estimate the extent of the spring catchment and infer the hydrogeological characteristics of the karst system. Of particular importance was the information obtained from the fluctuations of spring discharge and electrical conductivity in response to diurnal snowmelt cycles. Synthesis of the diverse data set indicates that the karst system has a large volume of groundwater stored in the fractured rock matrix that buffers the interannual variability of precipitation and sustains steady baseflow throughout the year. The karst system consists of fractured rock matrix, saturated conduits acting like pipes, unsaturated conduits acting like open channels, and many pools delaying the propagation of transport and hydraulic signals through the conduit network. The approach developed in this study will be applicable to other alpine karst systems in snow-dominated catchments in rugged and inaccessible terrains.

NMR spectroscopy has been widely used for the identification and structural elucidation of key components found in essential oils. For many years, the combination of NMR spectroscopy with other analytical techniques, such as gas chromatography (GC) and mass spectrometry (MS), has allowed researchers to identify and quantify a wide variety of terpenes, terpenoids, aldehydes, and other very low-level components present in various essential oils. Importantly, however, whereas GC continues to be the most widely used technique for the quantification of these components, NMR spectroscopy is still mostly reserved for structural elucidation purposes. In this work, we demonstrate how benchtop NMR spectroscopy can also be used for the quantification of key species in various essential oils, increasing accessibility to this technique by decreasing the costs associated with traditional high-field NMR instrumentation and lowering the expertise barriers required for accessing this technique.