PRISM :: Browsing by Author "Mayer, Bernhard"

Browsing by Author "Mayer, Bernhard"

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Open Access
Application of Geochemical and Isotopic Tracers for Characterization of SAGD Waters and Production Well Scale
(2018-01-21) Ciszkowski, Christine; Mayer, Bernhard; Cey, Edwin; Ryan, Cathryn; Mayer, Bernhard
Precipitation of scale minerals is common in SAGD operations and can severely hinder production. As scaling conditions and processes are not fully understood, select geochemical and isotopic (2H, 18O, 11B, 13C, 34S and 87Sr/86Sr) tracers were measured for SAGD waters and production well scale in order to characterize different fluids and identify source contributors towards scale formation. Pre-steamed pore water, bottom water (BW), steam condensate and produced water had distinct Na and Cl concentrations and water isotope compositions (2H, 18O). Distinct 11B, 13CDIC, 34SSO4 values and 87Sr/86Sr ratios of different SAGD waters enabled differentiation of BW from thermally altered waters (steam condensate and produced waters). SEM and bulk mineral chemical analyses identified quartz as the primary (~90 wt.%) scale mineral, while δ11B, δ34SSULFIDE, δ13CCARBS values of scale minerals indicated that they were precipitated from thermally altered waters and not as a result of formation water outside the steam chamber.
Open Access
Application of multiple-isotope and groundwater-age data to identify factors affecting the extent of denitrification in a shallow aquifer near a river in South Korea
(Springer, 2018-01-16) Kaown, Dugin; Koh, Eun-Hee; Mayer, Bernhard; Kim, Heejung; Park, Dong Kyu; Park, Byeong-Hak; Lee, Kang-Kun
The extent of denitrification in a small agricultural area near a river in Yangpyeong, South Korea, was determined using multiple isotopes, groundwater age, and physicochemical data for groundwater. The shallow groundwater at one monitoring site had high concentrations of NO3-N (74–83 mg L−1). The δ15N-NO3 values for groundwater in the study area ranged between +9.1 and +24.6‰ in June 2014 and +12.2 to +21.6‰ in October 2014. High δ15N-NO3 values (+10.7 to +12.5‰) in both sampling periods indicated that the high concentrations of nitrate in the groundwater originated from application of organic fertilizers and manure. In the northern part of the study area, some groundwater samples showed elevated δ15N-NO3 and δ18O-NO3 values, which suggest that nitrate was removed from the groundwater via denitrification, with N isotope enrichment factors ranging between −4.8 and −7.9‰ and O isotope enrichment factors varying between −3.8 and −4.9‰. Similar δD and δ18O values of the surface water and groundwater in the south appear to indicate that groundwater in that area was affected by surface-water infiltration. The mean residence times (MRTs) of groundwater showed younger ages in the south (10–20 years) than in the north (20–30 years). Hence, it was concluded that denitrification processes under anaerobic conditions with longer groundwater MRT in the northern part of the study area removed considerable amounts of nitrate. This study demonstrates that multi-isotope data combined with physicochemical data and age-dating information can be effectively applied to characterize nitrate contaminant sources and attenuation processes.
Open Access
Assessing Solute Sources and Chemical Weathering Reactions in the Kettle River Basin, British Columbia
(2012) Harker, Leslie Laura; Hutcheon, Ian E.; Mayer, Bernhard
Open Access
Assessing the usefulness of stable isotope data for estimating snowmelt contributions to runoff in the headwaters of the south Saskatchewan river basin, Alberta, Canada
(2009) Hogue, Kathryn J.; Mayer, Bernhard
Open Access
Assessment of the usefulness of the isotopic composition of surface water nitrate (d15N and d18O) for identifying its sources in a watershed with differing land use
(2005) Rock, Luc; Mayer, Bernhard
Open Access
Baseline soil gas characterization at a pilot CO2 injection site in Alberta, Canada
(2023-05-26) Riley, Dylan James Terence; Mayer, Bernhard; Nair, Rajeev Kumar Sasidharan; Ryan, Cathy
A baseline soil gas characterisation was performed on the upper 2.0 m of the CO2 and CH4 soil gas system at CMC’s Containment and Monitoring Institute, a geological CO2 storage field research station. Part of this characterisation was to investigate potential gas migration (GM) at the site’s infrastructure (wells and boreholes). Constant depth soil gas surveys following the endorsed methods outlined in the Alberta Energy Regulator's (2016) Directive-020 guideline were performed at six new wells, five legacy boreholes and three background locations at the site. Additionally, multi-level soil gas sampling surveys were conducted at four new wells and three background locations. Soil gas samples were analysed for CO2, N2, O2, CH4, ẟ13CCO2, and ẟ13CCH4. Soil gas surveys were conducted in the spring, summer and fall in 2017 and 2018. Additionally, SCVF was investigated at three new wells on site. The baseline soil gas characterisation concluded soil gas methane was likely sourced from the atmosphere and that there was no detectable GM present in the soil surrounding any of the site’s ground penetrations. However, GM was confirmed at one well during previous sampling in 2016, but its duration lasted less than one year. SCVF composed principally of methane (i.e. 7.4% to 97.3%) measured at three wells, was predominantly of biogenic origins with minor contributions from immature thermogenic methane. The SCVF at all three wells was sourced from the same zone, 195 m – 200 m bgs. The GM from the one well was noted as being of the same origins and source depth as the SCVF. The CO2 soil gas baseline conditions at the site demonstrated the CO2 was naturally sourced predominantly from biological respiration with minor inputs from methane oxidation. The baseline assessment found no evidence of exogenous CO2 in the soil gas system. Spatial (horizontal and vertical) and temporal (seasonal) variation in [CO2] and ẟ13CCO2 values across the site was demonstrated to be statistically significant. Ultimately, the baseline soil gas characterisation will be used to compare against future surveys to determine if CO2 leakage has occurred from the CO2 storage reservoir and migrated into the shallow vadose zone.
Open Access
Biogeochemical evidence of anaerobic methane oxidation and anaerobic ammonium oxidation in a stratified lake using stable isotopes
(Copernicus Publications, 2020-10-23) Einsiedl, Florian; Wunderlich, Anja; Sebilo, Mathieu; Coskun, Ömer K.; Orsi, William D.; Mayer, Bernhard
Nitrate pollution of freshwaters and methane emissions into the atmosphere are crucial factors in deteriorating the quality of drinking water and in contributing to global climate change. The n-damo (nitrite-dependent anaerobic methane oxidation), nitrate-dependent anaerobic methane oxidation and the anaerobic oxidation of ammonium (anammox) represent two microbially mediated processes that can reduce nitrogen loading of aquatic ecosystems and associated methane emissions to the atmosphere. Here, we report vertical concentration and stable-isotope profiles of CH4, NO−3, NO−2, and NH+4 in the water column of Fohnsee (lake in southern Bavaria, Germany) that may indicate linkages between denitrification, anaerobic oxidation of methane (AOM), and anammox. At a water depth from 12 to 20 m, a methane–nitrate transition zone (NMTZ) was observed, where δ13C values of methane and δ15N and δ18O of dissolved nitrate markedly increased in concert with decreasing concentrations of methane and nitrate. These data patterns, together with the results of a simple 1-D diffusion model linked with a degradation term, show that the nonlinear methane concentration profile cannot be explained by diffusion and that microbial oxidation of methane coupled with denitrification under anaerobic conditions is the most parsimonious explanation for these data trends. In the methane zone at the bottom of the NMTZ (20 to 22 m) δ15N of ammonium increased by 4 ‰, while ammonium concentrations decreased. In addition, a strong 15N enrichment of dissolved nitrate was observed at a water depth of 20 m, suggesting that anammox is occurring together with denitrification. The conversion of nitrite to N2 and nitrate during anammox is associated with an inverse N isotope fractionation and may explain the observed increasing offset (Δδ15N) of 26 ‰ between δ15N values of dissolved nitrate and nitrite at a water depth of 20 m compared to the Δδ15Nnitrate-nitrite of 11 ‰ obtained in the NMTZ at a water depth between 16 and 18 m. The associated methane concentration and stable-isotope profiles indicate that some of the denitrification may be coupled to AOM, an observation supported by an increased concentration of bacteria known to be involved in n-damo/denitrification with AOM (NC10 and Crenothrix) and anammox (“Candidatus Anammoximicrobium”) whose concentrations were highest in the methane and ammonium oxidation zones, respectively. This study shows the potential for a coupling of microbially mediated nitrate-dependent methane oxidation with anammox in stratified freshwater ecosystems, which may be important for affecting both methane emissions and nitrogen concentrations in lakes.
Open Access
Characterization and Control of Halophilic Sulfate-Reducing and Methanogenic Microbial Communities in Shale Oil and Gas Systems
(2017) An, Biwen Annie; Voordouw, Gerrit; Gieg, Lisa; Harrison, Joe; Mayer, Bernhard; Mouser, Paula
In recent years, the oil and gas industry has been revolutionized by the expansion of shale oil and shale gas operations due to the advancement of hydraulic fracturing and high economic benefits compared to other unconventional resources. Several mechanisms have been proposed for the possible roles of microorganisms in shale gas fields. However, there remains a lack of knowledge regarding the key microbial players shared by all shale reservoirs and their involvements in the operations. Three case studies were conducted using samples obtained from various shale oil and shale gas reservoirs on the possibility of reservoir souring, microbiologically influenced corrosion (MIC) and microbially enhanced oil recovery (MEOR) through both culture-dependent and independent approaches. Case study I, for the Bakken shale oil field in Saskatchewan Canada, showed that continuous injection of low salinity source water can alter the microbial and geochemical conditions of the reservoir. There is a dominance of halophilic microbial community in the saline shale formations, in which Halanaerobium can synthesize the substrates used by halophilic sulfate-reducing bacteria (SRB) for sulfate-reduction, and halophilic nitrate-reducing bacteria (NRB) can inhibit the growth of SRB through nitrite production. At low salinity, the microbial community is much more diverse involving Halanaerobium, Desulfovibrio, Thiomicrospira, Dethiosulfatibacter and Arcobacter, with high potential for souring and MIC. In addition, at low salinity, nitrate-mediated souring control cannot be as easily achieved as nitrite is further reduced to N2. Case studies II and III were for the Duvernay shale gas field and Montney shale oil field in Alberta, Canada, which showed high MIC potential involving similar halophilic taxa as found in the Bakken field. Finally, samples from all three case studies indicated higher salinities were associated with higher ammonium concentrations, which is a product of methylotrophic methanogenesis using methylamines. The addition of methylamines in the hydraulic fracturing process can facilitate the possible interactions between the key players identified in all three case studies. Through this work, mitigation and monitoring technologies targeting recurring taxa involved in shale reservoirs on souring and MIC can be developed, which is highly beneficial for the environment and the economy.
Open Access
Considering multiple anthropogenic threats in the context of natural variability: Ecological processes in a regulated riverine ecosystem
(Wiley, 2020-06-09) Sinnatamby, R. Niloshini; Mayer, Bernhard; Kruk, Mary K.; Rood, Stewart B.; Farineau, Anne; Post, John R.
Rivers are among the most altered environments globally, but identifying which threats are responsible for observed biotic and abiotic changes is complicated by natural drivers of variation. The Bow River, Canada provides an ideal model to resolve these influences and explore spatial relationships. It originates from pristine Rocky Mountain headwaters and is subsequently impacted by typical human alterations: damming, municipal channelization and effluent release, and agricultural impacts (nutrient enrichment and water withdrawal for irrigation). By coordinating studies of the Bow River's biota, we demonstrate how threat–driver interactions depend on season and the abiotic factor and biotic community or species of interest. We conclude that impact severity and riverine recovery depend on the threat magnitude, its longitudinal position and proximity to other threats and natural drivers. We found that river regulation, water extraction and bank armouring interact to limit geomorphic processes resulting in depleted riparian woodlands and numbers of fish species, though a large, undammed tributary nearby allows quick recovery downstream. We highlight the implications of the longitudinal position of the threats because cold-water fish species are disproportionately impacted through the area where the human impacts on the Bow River overlap. We illustrate how the interactions between flow, nutrients and temperature lead to macrophyte- or algae-dominated communities and associated shifts in fish composition and biomass. Finally, we applied our increased understanding of ecological riverine processes to conclude that management techniques such as flushing flows or functional environmental flows are likely to have only minimal or conditional success in the Bow River.
Open Access
Controls on the Isotopic Composition of Nitrite (δ15N and δ18O) during Denitrification in Freshwater Sediments
(Nature Research, 2019-12-16) Sebilo, Mathieu; Aloisi, Giovanni; Mayer, Bernhard; Perrin, Emilie; Vaury, Véronique; Mothet, Aurélie; Laverman, Anniet M
The microbial reduction of nitrate, via nitrite into gaseous di-nitrogen (denitrification) plays a major role in nitrogen removal from aquatic ecosystems. Natural abundance stable isotope measurements can reveal insights into the dynamics of production and consumption of nitrite during denitrification. In this study, batch experiments with environmental bacterial communities were used to investigate variations of concentrations and isotope compositions of both nitrite and nitrate under anoxic conditions. To this end, denitrification experiments were carried out with nitrite or nitrate as sole electron acceptors at two substrate levels respectively. For experiments with nitrate as substrate, where the intermediate compound nitrite is both substrate and product of denitrification, calculations of the extent of isotope fractionation were conducted using a non-steady state model capable of tracing chemical and isotope kinetics during denitrification. This study showed that nitrogen isotope fractionation was lower during the use of nitrite as substrate (ε = -4.2 and -4.5‰ for both treatments) as compared to experiments where nitrite was produced as an intermediate during nitrate reduction (ε = -10 and -15‰ for both treatments). This discrepancy might be due to isotopic fractionation within the membrane of denitrifiers. Moreover, our results confirmed previously observed rapid biotic oxygen isotope exchange between nitrite and water.
Open Access
Decadal Delays in Groundwater Recovery from Nitrate Contamination Caused by Low O2Reduction Rates
(Wiley Periodicals, Inc. on behalf of the American Geophysical Union, 2018-11-13) Wild, Lisa M.; Mayer, Bernhard; Einsiedl, Florian
Nitrate (NO urn:x-wiley:wrcr:media:wrcr23708:wrcr23708-math-0001) is one of the main pollutants in agriculturally impacted groundwater systems. The availability and reactivity of electron donors control the prevalent redox conditions in aquifers and past nitrate contamination of groundwater can be ameliorated if denitrification occurs. Using aqueous geochemistry data and the stable isotope composition of dissolved nitrate (δ15N and δ18O), we found that nitrate concentrations above the World Health Organization drinking water guideline were caused predominantly by manure and to a lesser extent by synthetic fertilizer applications and that denitrification was not a significant nitrate removal process in an aquifer in southern Germany underlying agricultural land with intensive hog farming. We also applied environmental isotopes (δ2H and δ18O, 3H/3He, and 14C) linked with a lumped parameter approach to determine apparent mean transit times (MTT) of groundwater that ranged from <5 years to >100 years. Furthermore, we determined low reduction rates of dissolved oxygen (O2) of 0.015 1/year for first-order kinetics. By extrapolating the O2 reduction rates beyond the apparent MTT ranges of sampled groundwater, denitrification lag times (time prior to commencement of denitrification) of approximately 114 years were determined. This suggests that it will take many decades to significantly reduce nitrate concentrations in the porous aquifer via denitrification, even if future nitrate inputs were significantly reduced.
Open Access
Differentiation of natural and anthropogenic contaminant sources using isotopic and microbial signatures in a heavily cultivated coastal area
(Elsevier, 2021-01-11) Kaown, Dugin; Koh, Eun-Hee; Mayer, Bernhard; Ju, YeoJin; Kim, Jaeyeon; Lee, Hye-Lim; Lee, Seong-Sun; Park, Dong Kyu; Lee, Kang-Kun
Hydrogeochemical and multiple isotope data for groundwater samples were obtained and interpreted to discriminate anthropogenic and natural contaminant sources in a coastal aquifer underlying a heavily cultivated watershed in Hwaseong, South Korea. The local aquifers are vulnerable to contamination, due to high anthropogenic N inputs and the location close to the ocean facilitating seawater intrusion. Thus, to effectively control the groundwater quality in the study area, it is necessary to differentiate between anthropogenic and natural contaminant sources. The concentrations of NO3-N in the groundwater ranged between 0.14 and 45.6 mg/L in August 2015 and 0.2-39.6 mg/L in March 2016. High concentrations of Cl- (388-1107 mg/L) and a high electrical conductivity (1027-2715 μS/cm) were observed in the study area, suggesting that the groundwater was affected by seawater intrusion. Furthermore, δ15N-NO3-, δ34S-SO42- values and 87Sr/86Sr of groundwater were determined to reveal the origins of the natural and anthropogenic contaminants and the groundwater mean residence times (MRT) and 87Sr/86Sr ratios were used to assess the hydrogeochemical processes along the flow path in the study area. Young groundwater was affected by an anthropogenic contamination source with contributions of 26-46% adding nitrate to the aquifer, whereas old groundwater was impacted by mixing with seawater with contributions of 10-20% with low concentrations of NO3-N, but elevated concentrations of chloride and sulfate. Recently recharged uncontaminated groundwater showed oxic conditions with a diverse microbial community structure, whereas young groundwater contaminated by anthropogenic sources showed a less diverse microbial community structure. The results of this study suggest that multiple isotopes combined with groundwater MRT and microbial data can be applied to distinguish natural and anthropogenic contaminant sources in a groundwater system.
Open Access
Effect of boiler feed water composition on inorganic scaling in once-through steam generators estimated using a Monte Carlo modelling approach
(Elsevier, 2022-11-22) Klyukin, Yury; Mayer, Bernhard; Tutolo, Benjamin
Once-through steam generators (OTSGs) produce steam required to recover hydrocarbons from oil sand deposits. OTSGs generate steam at high pressure and temperature, using boiler feed water (BFW) derived from produced water, recycled condensate boiler blowdown (BBD), and small amounts of make-up water sourced from local groundwater. During the OTSG operation cycle, BFW undergoes significant physical and chemical changes, which can cause varying degrees of mineral (scale) precipitation, depending on the BFW quality. Scaling has negative impacts on OTSG performance and has in the past resulted in OTSG tube leaks. In this study, we performed thermodynamic simulations using a Monte Carlo approach with the objective of determining how the composition of the BFW and the steam quality affect scaling. We used 3 different scenarios, characterized by low, intermediate, and high iron-to-BFW ratios to represent various situations of BFW inter- action with OTSG pipes. Within each scenario, BFW compositions were randomly assigned within industry- relevant variations of variables including steam quality, pH, and concentrations of SiO2(aq), Mg2+, Ca2+, Fe2+, Cl−, HCO3−, K+, Na+, SO4 2− and O2 and were allowed to precipitate scales according to thermodynamically controlled solubilities of minerals as they were heated and boiled. Our results show that inorganic scale in OTSGs is composed mostly of aegirine and various Mg and Mg/Ca silicates. We show that the concentrations of dissolved Si, Mg, and Fe available for interaction with BFW are the main factors controlling the mass and mineralogy of scale, whereas the total dissolved solids (TDS) and Ca concentrations within typical chosen operating limits have negligible impact on the scale mass in OTSGs. The modelling results further indicate that efforts to minimize the concentration of Mg in BFW to very low levels (<0.01 mg/kgBFW) show great promise for minimizing inorganic scale formation in OTSGs. Our equilibrium modelling revealed that steam quality has little impact on the total mass of inorganic scale formed in OTSGs because most of the mineral precipitation occurs at temperatures below 250 ◦C, before boiling starts. However, this finding may not be fully valid if strong kinetic barriers prevent process waters from achieving equilibrium via scale precipitation, especially at lower temperatures. Moreover, because nucleated minerals may be transported through the OTSG without precipitating on the piping walls, increasing steam quality reduces the capacity of BBD to carry over crystallized mineral phases in suspension.
Open Access
Effect of thermal maturity on remobilization of molybdenum in black shales
(Elsevier, 2016-09-01) Ardakani, Omid H.; Chappaz, Anthony; Sanei, Hamed; Mayer, Bernhard
Molybdenum (Mo) concentrations in sedimentary records have been widely used as a method to assess paleo-redox conditions prevailing in the ancient oceans. However, the potential effects of post-depositional processes, such as thermal maturity and burial diagenesis, on Mo concentrations in organic-rich shales have not been addressed, compromising its use as a redox proxy. This study investigates the distribution and speciation of Mo at various thermal maturities in the Upper Ordovician Utica Shale from southern Quebec, Canada. Samples display maturities ranging from the peak oil window (VRo∼1%) to the dry gas zone (VRo∼2%). While our data show a significant correlation between total organic carbon (TOC) and Mo (R2=0.40, n=28, P<0.0003) at lower thermal maturity, this correlation gradually deteriorates with increasing thermal maturity. Intervals within the thermally overmature section of the Utica Shale that contain elevated Mo levels (20–81 ppm) show petrographic and sulfur isotopic evidence of thermochemical sulfate reduction (TSR) along with formation of recrystallized pyrite. X-ray Absorption Fine Structure spectroscopy (XAFS) was used to determine Mo speciation in samples from intervals with elevated Mo contents (>30 ppm). Our results show the presence of two Mo species: molybdenite Mo(IV)S2 (39±5%) and Mo(VI)-Organic Matter (61±5%). This new evidence suggests that at higher thermal maturities, TSR causes sulfate reduction coupled with oxidation of organic matter (OM). This process is associated with H2S generation and pyrite formation and recrystallization. This in turn leads to the remobilization of Mo and co-precipitation of molybdenite with TSR-derived carbonates in the porous intervals. This could lead to alteration of the initial sedimentary signature of Mo in the affected intervals, hence challenging its use as a paleo-redox proxy in overmature black shales.
Open Access
Environmental Groundwater Vulnerability Assessment in Urban Water Mines (Porto, NW Portugal)
(Multidisciplinary Digital Publishing Institute, 2016-11-03) Afonso, Maria; Freitas, Liliana; Pereira, Alcides; Neves, Luís; Guimarães, Laura; Guilhermino, Lúcia; Mayer, Bernhard; Rocha, Fernando; Marques, José; Chaminé, Helder
A multidisciplinary approach was developed to estimate urban groundwater vulnerability to contamination combining hydrogeology, hydrogeochemistry, subterranean hydrogeotechnics, groundwater ecotoxicology and isotope tracers. Paranhos and Salgueiros spring waters in Porto City were used as a case study. Historical and current vulnerability scenarios were compared using hydrogeological GIS-based modelling. Potential contamination sources were mapped around the spring galleries. Most of these were point sources and their potential contamination load was moderate. The ecotoxicological assessment indicated a low acute toxicity potential. Groundwater radionuclides appeared to be mainly controlled by geological factors and biomineralisation. Vulnerability maps suggest that most of the area has a moderate to low vulnerability to contamination. However, some surface sources such as sewage systems cause contamination and contribute to increased vulnerability. This integrated approach was demonstrated to be adequate for a better knowledge of urban hydrogeological processes and their dynamics, and highlighted the importance of a vulnerability assessment in urban areas.
Open Access
Establishing High-Resolution Hydrogeological, Geochemical and Isotopic Baseline Conditions of the Fresh Water Zone at a Field Research Site Near Brooks, Alberta, Canada
(2019-12-20) Cheung, Terri Tze-Man; Mayer, Bernhard; Lawton, Don C.; Cey, Edwin E.; Tutolo, Benjamin M.
A high-resolution baseline characterization of dissolved gases in groundwater at the CMC field research site from 25.0 to 106.3 m depths was conducted. Data was collected from a continuously cored 106.3 m deep borehole, a 100.0 m deep Westbay® multi-level system and a 67.1 m deep domestic well. The multi-level well with 26 ports revealed variability and stratification in hydrogeology and hydrochemistry. Ports completed in coals had high flow rates and yielded sodium bicarbonate water type, water isotope compositions resembling local meteoric water, elevated methane and ethane concentrations, and biogenic d13C-CH4 values of <-82‰. Below the coals, ports were characterized by lower flow rates, higher d18O and d2H values of water and variable water types. Methane and ethane concentrations were lower compared to samples obtained from coals and d13C-CH4 values ranged between -75‰ and -60‰. The domestic well yielded groundwater with chemical and isotopic compositions resembling groundwater from only the high-flowing coal-containing aquifer portions.
Open Access
Foliage Chemistry of Pinus baksiana in the Athabasca Oil Sands Region, Alberta, Canada
(MDPI, 2016-12-08) Proemse, Bernadette; Maynard, Doug; Mayer, Bernhard
Industrial emissions in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, have caused concerns about the effect of oil sands operations on the surrounding terrestrial environments, including jack pine (Pinus banksiana Lamb.) stands. We collected jack pine needles from 19 sites in the AOSR (13–128 km from main operations) for foliar chemical analyses to investigate the environmental impact on jack pine. Pine needles from three age classes, the current annual growth (CAG, 2011), one year and two year old pine needles, were collected. Samples were analyzed for total carbon (TC), nitrogen (TN), and sulfur (TS), inorganic S (SO4-S), base cations (Ca, Mg, Na), and other elements (B, Cu, Fe, Mn, P, Zn); CAG needles were also analyzed for their nitrogen and carbon isotopic compositions. Only TN, TS, Ca, B, Zn, and Fe contents showed weak but significant increases with proximity to the major oil sands operations. C and N isotopic compositions showed no trend with distance or TC and TN contents. Total S contents in CAG of pine foliage increased significantly with proximity to the main industrial operation while foliar inorganic S to organic S ratios (SO4-S/Sorg) ranged consistently between 0.13 and 0.32, indicating low to moderately high S loading. Hence, this study suggests some evidence of uptake of S emissions in close proximity to anthropogenic sources, although the reported values have not reached a level of environmental concern.
Open Access
Free Phase Gas in Shallow Groundwater
(2022-08) Morais, Tiago Antonio; Mayer, Bernhard; Ryan, M. Cathryn; Mayer, Klaus Ulrich; McClain, Cynthia
The unintended migration of natural gases and saline fluids from deep formations into shallow aquifers can increase the risk of explosion during groundwater extraction, induce biogeochemical changes in aquifers containing potable groundwater, and increase greenhouse gas emissions into the atmosphere. Hence, long-term monitoring of gases present in shallow aquifers is essential to evaluate the occurrence and the potential environmental impacts associated with the presence of fugitive natural gas migration. However, accurate sampling and monitoring of dissolved and free-phase gases (FPG) is particularly challenging in gas-charged groundwater wells. In addition, the fate of fugitive natural gases in shallow aquifers around oil and gas wells with gas migration is not yet fully understood. This thesis investigates the best approaches for accurate monitoring and sampling of dissolved gases and FPG in shallow aquifers. In addition, a multidisciplinary field investigation was conducted around an oil and gas well with integrity failure to investigate the key mechanisms that govern transport and attenuation of fugitive gases in the shallow groundwater zone. Monitoring of Total Dissolved Gas Pressure (PTDG) and dissolved gas concentrations in a 'gassy' groundwater well demonstrated that bubble exsolution (i.e., FPG formation), bubble-driven micro advection, and thermally driven convection are key mechanisms controlling degassing in gas-charged groundwater wells. In addition, laboratory experiments indicated that the combined measurement of water pressure, electrical conductivity, and PTDG can accurately identify the occurrence of FPG in groundwater wells under non-flowing and flowing conditions. Finally, high-resolution monitoring of fugitive gases and hydrogeological conditions in the shallow groundwater zone around an oil and gas well with gas migration demonstrated that the transport of fugitive gases at the study well is controlled by the presence of preferential pathways along the well casing, the distribution of lenses of unconsolidated sediments with higher silt and clay content, and the groundwater flow direction. Together, these findings provided insights into the key mechanisms controlling in-well degassing in gas-charged wells, the usage of water pressure and continuously measured field parameters to detect the occurrence of FPG in groundwater wells, and the transport of fugitive natural gases in shallow aquifers around 'leaky' oil and gas wells.
Open Access
From Greensands to Green Technology: Examination of Carbon Dioxide Storage Potential in Glauconitic Sandstones
(2022-05) Zhang, Qin; Tutolo, Benjamin; Mayer, Bernhard; Clarkson, Christopher; Hubbard, Stephen; Meyer, Rodolfo; Wilson, Siobhan
Glauconite is a divalent cation-bearing mineral abundant in sedimentary rocks and hydrocarbon reservoirs worldwide, and it may be important for ongoing efforts to geologically store anthropogenic CO2. Since glauconite naturally contains both Fe(II) and Fe(III) in its mineral structure, it can also be leveraged to constrain paleoenvironmental redox conditions. Nevertheless, because of its complex mineralogy and redox sensitivity, thermodynamic and kinetic properties of glauconite have been difficult to constrain. This thesis has been devoted to fill this significant knowledge gap. Chapter 2 contains a detailed evaluation of the mechanisms through which carbonate minerals naturally replace glauconite during diagenesis of glauconitic sandstones from the Mannville Group in Alberta, Canada. Using a combination of petrological and geochemical analyses, we show that glauconite carbonation is a reduction-facilitated, coupled glauconite recrystallization and siderite precipitation reaction, which is accompanied by a significant reduction of Fe. These results suggest that geochemical conditions, most importantly, temperature, partial pressure of CO2, and fluid redox state were thermodynamically favorable for glauconite carbonation during burial diagenesis of Mannville Group glauconitic sandstones. Chapter 3 quantifies the far-from-equilibrium rates of glauconite dissolution using a novel experimental apparatus specifically designed to explore mineral dissolution kinetics under strictly anaerobic conditions. Steady-state glauconite dissolution rates were measured at varying pH from 1.7 to 11.2 and temperature from 24 to 80 °C. The experimental results show stoichiometric or close-to-stoichiometric glauconite dissolution for Fe, Mg and Si. In comparison to previous studies, we emphasize that the mechanism of glauconite dissolution is determined by redox condition and temperature, and the dissolution rates are pH-dependent in acidic conditions and pH-independent in natural to basic pH. Chapter 4 uses calculations based on 11,652 well logs to show that glauconitic sandstones offer significant and previously overlooked potential for sedimentary reservoir-based mineral carbonation. Our results demonstrate that hundreds of gigatons of CO2 could be sequestered by carbonating the immense quantity of glauconite underlying Alberta, Canada alone. Together, these findings suggest that glauconite had been underestimated both in terms of availability and reactivity, and these new findings provide important insights to re-evaluate CO2 storage in sedimentary basins.
Open Access
Fugitive Gas Migration in the Vadose Zone at an Experimental Field Site in the Montney Shale Gas Region
(Wiley Subscription Services, Inc., 2022-01) Forde, Olenka N.; Cahill, Aaron G.; Mayer, Bernhard; Beckie, Roger D.; Mayer, K. Ulrich
Fugitive gas migration (GM) from compromised oil and gas wells remains a global concern. To understand environmental impacts from GM there is a need to characterize the transport and fate of fugitive gas in the vadose zone. We simulated subsurface wellbore leakage by injecting natural gas into thick unsaturated glacio-lacustrine deposits in a region of petroleum development in Western Canada. Methane and carbon dioxide effluxes were monitored and soil-gas samples were collected for molecular and stable carbon isotope analyses. A conceptual model was developed to demonstrate the physical and biogeochemical processes that control the spatial-temporal variability of GM. Methane oxidation partially attenuated natural gas; however, gas transport and fate were strongly influenced by variations in grain-size distribution and barometric pressure, resulting in episodic effluxes and lateral gas transport. To accurately detect, quantify and assess GM at oil and gas sites, adequate site characterization and continuous, spatially dense monitoring are necessary.