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Researchers in the Faculty of Science are involved in an impressive variety of fields – from astrophysics to zoology, nanotechnology to virtual reality, metabolomics to mathematics and much more!

In all cases, our faculty researchers, post-doctoral fellows, and graduate and undergraduate students live up to the highest standards in their disciplines, seeking to expand human knowledge through curiosity, innovation, and discovery.

Faculty of Science

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Open Access
Alkalinity Generation Constraints on Basalt Carbonation for Carbon Dioxide Removal at the Gigaton-per-Year Scale
(2021-08-20) Tutolo, Benjamin M; Awolayo, Adedapo; Brown, Calista
The world adds about 51 Gt of greenhouse gases to the atmosphere each year, which will yield dire global consequences without aggressive action in the form of carbon dioxide removal (CDR) and other technologies. A suggested guideline requires that proposed CDR technologies be capable of removing at least 1% of current annual emissions, about half a gigaton, from the atmosphere each year once fully implemented for them to be worthy of pursuit. Basalt carbonation coupled to direct air capture (DAC) can exceed this baseline, but it is likely that implementation at the gigaton-per-year scale will require increasing per-well CO2 injection rates to a point where CO2 forms a persistent, free-phase CO2 plume in the basaltic subsurface. Here, we use a series of thermodynamic calculations and basalt dissolution simulations to show that the development of a persistent plume will reduce carbonation efficiency (i.e., the amount of CO2 mineralized per kilogram of basalt dissolved) relative to existing field projects and experimental studies. We show that variations in carbonation efficiency are directly related to carbonate mineral solubility, which is a function of solution alkalinity and pH/CO2 fugacity. The simulations demonstrate the sensitivity of carbonation efficiency to solution alkalinity and caution against directly extrapolating carbonation efficiencies inferred from laboratory studies and small-injection-rate field studies conducted under elevated alkalinity and/or pH conditions to gigaton-per-year scale basalt carbonation. Nevertheless, all simulations demonstrate significant carbonate mineralization and thus imply that significant mineral carbonation can be expected even at the gigaton-per-year scale if basalts are given time to react.
Open Access
Anatomy of a buried thrust belt activated during hydraulic fracturing
(2020-10-18) Riazi, Naimeh; Eaton, David W.
Tectonically active fault networks are often inter-connected, but in the case of injection-induced seismicity, prior knowledge of fault architecture tends to be severely limited. In most cases, reactivated faults due to fluid injection are inferred, after-the-fact, by the spatial distribution of induced-seismicity hypocenters; such reliance on post-injection seismicity impedes any pre-operational risk analysis, as well as development of a more holistic understanding of fault-system models. By combining high-resolution, depth-migrated 3-D seismic data with a new focal-depth estimation method that reduces spatial uncertainty of hypocenters, this study pinpoints microearthquake fault activation within a buried thrust belt in the Montney Formation in western Canada (British Columbia). During hydraulic-fracturing operations, rupture nucleation occurred on seismically imaged thrust ramps that cut through the Debolt Formation, a massive carbonate layer that underlies the stimulated zone. High-resolution seismic images reveal transverse structures, interpreted as basement-controlled fold hinges or tear faults that transferred displacement between thrust faults during Late Cretaceous - Paleogene compressional shortening. The spatio-temporal pattern of induced seismicity suggests that these transverse structures provide permeable pathways for aseismic pore-pressure diffusion, thus connecting distinct thrust faults and enabling earthquake triggering on a timescale of days and at distances of up to 2 km from the injection wells. Inferred relationships highlight how the fault system is connected, including apparent stress concentrations at the intersections of transverse structures and orogen-parallel thrust ramps.
Open Access
Application of Focal-Time Analysis for Improved Induced Seismicity Depth Control: A Case Study from the Montney Formation, British Columbia, Canada
(2020-08-10) Riazi, Naimeh; Eaton, David W.; Aklilu, Alemayehu; Poulin, Andrew
Characterization of induced seismicity and associated microseismicity is an important challenge for enhanced oil recovery and development of tight hydrocarbon reservoirs. In particular, accurately correlating hypocenters of induced events to stratigraphic layers plays an important role in understanding the mechanisms of fault activation. Existing methods for estimating focal depth, however, are prone to a high degree of uncertainty. A comprehensive analysis of inferred focal depths is applied to induced events that occurred during completions of horizontal wells targeting the Montney Formation in British Columbia, Canada. Our workflow includes a probabilistic, nonlinear global-search algorithm (NonLinLoc), a hierarchical clustering algorithm for relative relocation (GrowClust) and depth refinement using the recently developed focal-time method. The focal-time method leverages stratigraphic correlations between P-P and P-S reflections to eliminate the need for an explicit velocity model developed specifically for hypocenter depth estimation. We show that this approach is robust in the presence of noisy picks and location errors from epicenters obtained using a global-search algorithm, but it is limited to areas where multicomponent 3-D seismic data are available. A novel method to determine statics corrections is developed here, to ensure that both passive seismic observations and 3-D seismic data share a common datum in areas of moderate to high topography. Our results highlight the importance of transverse faults, which appear to provide permeable pathways for activation of other faults at distances of up to 2 km from hydraulic fracturing operations.
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 and Mapping Groundwater Vulnerability to Bacteria in Alberta
(2017-04) Van Staden, Tamara
Aquifer vulnerability index methods are commonly used for assessing groundwater vulnerability to surface contaminants. However, the methods have primarily been developed for dissolved contaminants. Microbial contaminants have unique characteristics that result in different transport behavior in the subsurface, and thus different tools need to be designed. Key vulnerability factors specific to microbial sources and subsurface transport mechanisms were identified in this study and incorporated into a model using an ArcGIS framework to create provincial-scale maps of groundwater vulnerability, specific to E. coli, in Alberta for the year 2012. Examples of these factors include: soil texture based on grain size, soil organic matter, hydrogeologic properties, depth to aquifer, and meteorological conditions. These factors were combined from individual GIS layers to create an intrinsic vulnerability map, demonstrating where aquifers were more vulnerable to bacterial contamination if a source became present. Maps were created for the growing season and cold season, and attempts were made to test the model with E. coli detection data. The results of these statistics were not significant enough for this model to be used for predictive purposes, but this could be caused by the presence or lack of risk (i.e., source of contaminants), as opposed to real differences in aquifer vulnerability. This project helped inform which factors should be considered when making a vulnerability map for bacterial contaminants, most notably temporal factors such as precipitation and soil moisture. The developed map provided insights as to where shallow aquifers in Alberta are intrinsically vulnerable to bacterial contamination.
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
Calibrating infrasonic to seismic coupling using the Stardust sample return capsule shockwave: Implications for seismic observations of meteors
(American Geophysical Union, 2007-10-18) Edwards, Wayne N.; Eaton, David W.; McCausland, Philip J.; ReVelle, Douglas O.; Brown, Peter G.
Open Access
Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging
(Oxford University Press, 2021-11-04) Jia, Suzie; Wong, Ron; Eaton, David
Crack nucleation and rock failure processes in a fine-grained siltstone (Montney Formation) under triaxial compression are investigated using combined diagnostic techniques, including ultrasonic-wave measurement, acoustic-emission (AE) monitoring, computed tomography (CT) scanning, and thin-section imaging. The sample displays a weak-to-moderate inherent seismic anisotropy and noticeable stress-induced anisotropy prior to failure. No AE event was detected until the applied axial stress reached 95% of the peak value. The signal-to-noise ratio is relatively low, however, and detectable AE events are more diffuse than those observed in highly brittle rocks. The AE locations correlate with a shear fracture zone imaged by CT scanning. AE moment-tensor analysis reveals that events with larger relative magnitudes are characterized by high volumetric (tensile or compressive) components, and the initiation of the failure zone is dominated by combined shear-tensile failure. Stress inversion of the AE events with high tensile components is in good agreement with the known applied stress. Microscopic imaging of thin sections from the failed sample shows that the failure zone is an en echelon structure consisting of a major fracture with branching micro and minor cracks. This failure mechanism is consistent with a shear-tensile source mechanism and is interpreted to be associated with the fine granular structure and mineral composition of Montney siltstone.
Open Access
The contribution of aqueous catechol-silica complexes to silicification during carbonate diagenesis
(J.GCA, 2020-04) Escario Perez, Sofia; Nightingale, Michael; Humez, Pauline; Tutolo, Benjamin M.
Pore-filling and carbonate-replacing silica is exceedingly common in carbonates, but the fundamental geochemical mechanisms that drive these silicification reactions during diagenesis remain poorly understood. An existing mode has proposed that carbonate silicification proceeds through an interface-coupled dissolution-precipitation reaction, but it lacks a mechanism that enables pore fluids to reach the requisite level of supersaturation with respect to silica to allow nucleation and growth. Here, we present a sequence of batch experiments ranging in duration from 7 to 49 days designed to test the hypothesis that these reactions are facilitated by the formation and destruction of organo-silica complexes during diagenesis. Our results illustrate that the stability of organo-silica complexes is dependent upon the concentration of organic molecules in solution, as well as pH, 16 salinity, and solution redox state. Together, these results allow us to present the following scheme for organo-silica complex mediation of silicification reactions: Firstly, the breakdown of organic matter in the presence of siliceous material creates organo-silica complexes, leading to silica-enriched pore fluids, a process which is enhanced by the anoxic conditions accompanying sediment burial. Then, as environmental conditions evolve (fO2, salinity, light, fCO2, pH...), the stability of the organo-silica complexes diminishes, and the organo-silica complexes break down. Simultaneously, the pore fluids become intensely silica-supersaturated in direct proportion to the amount of organic material remaining in solution. The resulting supersaturation drives carbonate silicification via the precipitation of silica minerals, a process which is aided by the presence of silica “nuclei” (such as sponge spicules). This study contributes new data and a conceptual model that will aid in the ongoing quest to understand carbonate silicification reactions and their potential applications in hydrocarbon exploitation and geologic CO2 storage. Moreover, it helps to explain the common association between silica precipitates and organic mineral in the sedimentary rock record.
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
The elusive lithosphere-asthenosphere boundary (LAB) beneath cratons
(Elsevier, 2009-04) Eaton, David W.; Darbyshire, Fiona; Evans, Rob L.; Grütter, Herman; Jones, Alan G.; Yuan, Xiaohui
Open Access
Empirical transfer functions: Application to determination of outermost core velocity structure using SmKS phases
(American Geophysical Union, 2007) Alexandrakis, Catherine; Eaton, David W.
Open Access
Enhancing base-metal exploration with seismic imaging
(NRC Research Press, 2010-05-01) Eaton, David W.; Adam, Erick; Milkereit, Bernd; Salisbury, Matthew; Roberts, Brian; White, Don; Wright, James
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
Estimation of fracture height growth in layered tight/shale gas reservoirs using flowback gas rates and compositions–Part II: Field application in a liquid-rich tight reservoir
(Elsevier, 2016-01) Clarkson, C.R.; Ghaderi, S.M.; Kanfar, M.S.; Iwuoha, C.S.; Pedersen, P.K.; Nightingale, M.; Shevalier, M.; Mayer, B.
While hydraulic fracturing is the key to unlocking the potential of unconventional low-permeability hydrocarbon resources, challenges remain in the monitoring of subsurface propagation of fractures and the determination of which geologic intervals have been contacted. This is particularly challenging for wells that are completed in multiple hydraulic fracture stages (multi-fractured horizontal wells or MFHWs) where fracture spacing may be very close and fracture geometry complex. Understanding the fracture extent is important not only for assisting with hydraulic fracture design, but also for mitigating unwanted fracture growth into non-target geologic intervals that do not contain hydrocarbons (e.g. zones with high water saturation). Popular current technologies used for hydraulic fracture surveillance include microseismic (surface and subsurface monitoring) and tiltmeter surveys. While these methods have proven useful for characterizing the extent of created hydraulic fractures, they do not necessarily lead to an understanding of what portions of the geologic section (bounding and target intervals for MFHWs, for example) are in direct hydraulic communication with the well. A solution for establishing the extent of hydraulic fracture growth from target to bounding zones is to first obtain a fluid composition fingerprint of those intervals while drilling through them, and then compare these data with fluid compositions obtained from flowback after hydraulic fracturing. In the current work, a MFHW completed in a liquid-rich tight reservoir is used to test this novel concept. Gas samples extracted from the headspace of isojars® containing cuttings samples, obtained during drilling of the MFHW well, were used to geochemically fingerprint geologic intervals through which the well was drilled. The cuttings samples were collected at high frequency in the vertical, bend and lateral sections of the well over a measured depth range of 4725 ft (1440 m). A compositional marker was identified in the bend of the horizontal well above which the average methane to ethane (C1/C2) ratio was 15.7, versus 2.6 below it. The flowback gas compositions were observed to be intermediate (average C1/C2 = 7.4) between the reservoir above and below the marker, suggesting fracture height grew above the compositional marker. In order to estimate fracture height growth from the geologic interval and flowback compositions, a compositional numerical simulation study was performed. An innovative approach was used to estimate recombined in-situ fluid compositions, on a layer-by-layer basis, by combining the cuttings gas compositional data with separator oil compositions. The resulting numerical simulation model, initialized through use of the layered fluid model and a detailed geological model developed for the subject well and offset drilling locations, was used to history match flowback rates, pressures and gas compositions. The gas compositions of the fingerprinted geologic intervals were therefore employed as a constraint on fracture height growth, estimated in the model to be 175 ft (53 m, propped height). However, because of the uncertainty in model input parameters, a stochastic approach was required to derive a range in hydraulic fracture properties. The current study demonstrates for the first time that it is possible to constrain fracture height growth estimates from flowback data, combined with gas compositional data obtained from cuttings data, provided that the geochemical fingerprints are distinct.
Open Access
Evaluation of the potential of glauconite in Western Canadian Sedimentary Basin for large-scale carbon dioxide mineralization
(Elsevier, 2022-04) Zhang, Qin; Tutolo, Benjam.M.
Geologic carbon dioxide (CO2) storage is an essential and economical measure to mitigate global climate change. CO2 storage potential in sedimentary reservoirs is commonly passed over in favor of more reactive rock formations, such as basalts, because the latter offer rapid, permanent storage as carbonate minerals while the former are thought to only offer less permanent physical trapping of CO2. Nevertheless, recent research has demonstrated that carbonation reactions in glauconitic sandstones are favorable under realistic reservoir conditions, although the overall availability of glauconite for carbonation has not yet been quantified. Here, we use 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. Importantly, these glauconitic sandstones, and others worldwide, have long been exploited for their favorable hydrocarbon production capacity. Thus, global societies eager to limit greenhouse gas emissions may need to look no further than the reservoirs they are already exploiting. Moreover, because the requisite injection infrastructure is oftentimes still active, glauconitic sandstones may present the highest priority, lowest capital cost substrate for mineral carbonation worldwide.
Open Access
Field guide to the geology, metamorphism and tectonics of the Foreland and Omineca belts of SW Alberta and SE British Columbia
(2020-10) Pattison, David R.M.; Moynihan, David P.; McFarlane, Christopher R.M.; Simony, Philip S.; Cubley, Joel F.
This field guide describes field localities that illuminate the geology, metamorphism and tectonics of the Foreland and Omineca belts of the southern Canadian Cordillera in southwestern Alberta and southeastern British Columbia. The Omineca belt contains the deformational, magmatic and metamorphic record of the Jurassic through Eocene development of this part of the Cordilleran orogen. Calgary, where the field trip starts, is situated just east of the edge of the Cordilleran deformation belt, so the geology of the famous Foreland fold and thrust belt is examined on the way to the Omineca belt. A theme of the field guide is that the structural, magmatic and metamorphic processes that occurred in the Omineca belt were intimately linked to the structural and sedimentary processes occurring at the same time in the Foreland belt. The geological domains covered by the field guide include (from east to west) the Foreland thrust and fold belt, Rocky Mountain Trench, Purcell anticlinorium, Kootenay arc, Quesnel terrane, and two Shuswap-type Cordilleran core complexes, the Valhalla complex and Grand Forks complex. The cities and towns within the geographic area covered by the field guide include (from east to west) Calgary and Banff (both in Alberta) and the following communities in British Columbia: Radium, Cranbrook, Kimberley, Creston, Riondel, Kaslo, Nelson, Salmo, Castlegar, Christina Lake and Grand Forks. The field guide covers all aspects of the geology traversed by the field trip. It comprises ten segments based on a combination of geology and geography. The field trip segments are preceded by an overview of the physiography, present-day geophysics, stratigraphy, magmatism, metamorphism, tectonics, ore deposits and geomorphology of the southern Canadian Cordillera. The field guide comprises 82 Stops, 49 Optional stops and 40 Road logs, and is illustrated with 114 figures comprising maps, diagrams, photographs and photomicrographs. Note: the field guide is large (~228 MB), so it may take some time to download.