Browsing by Author "Tutolo, Benjamin"

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    CO2 Sequestration through Mineral Carbonation
    (2022-10-18) Bader, Alex; Clarkson, Christopher; Tutolo, Benjamin; Meyer, Rodolfo
    Anthropogenic greenhouse gas emissions have become a subject of increasing concern because of their association with global climate change. Carbon dioxide (CO2) is the most prevalent anthropogenic greenhouse gas, and hence reduction of CO2 concentration in the atmosphere has become an important area of research. Subsurface (geologic) storage has been proposed as a target for CO2 storage; physical, residual and solubility trapping are possible storage mechanisms. An additional promising mechanism for geologic CO2 storage is permanent fixation by means of mineral trapping. This thesis explores the use of unconventional reservoirs such as shales and siltstones as a target for mineral trapping of CO2. Although some studies of CO2 storage in shales and low-permeability (tight) reservoirs exist, most previous studies of shales related to CO2 storage have primarily focused on the evaluation of shale as a caprock to contain CO2 within more conventional reservoirs. Such studies have concentrated on caprock mechanical integrity as it pertains to leakage instead of reactivity or geochemical modification in the shale. In this research, CO2 storage in shales and siltstones is evaluated with a focus on the potential for mineral trapping. An innovative workflow and custom reactor were designed to evaluate this potential for low-permeability Montney siltstone and Duvernay shale samples, and specifically their interaction with CO2-charged brine at simulated reservoir conditions. Prior to analysis of the Montney and Duvernay samples, olivine samples were studied with the new workflow/reactor as a proof of concept. Olivine is well-known to generate carbonate at high CO2 pressures (PCO2) and high temperature in alkaline solutions. San Carlos Olivine was therefore used as a control group and tested at 150°C/150bar in a 1M NaCl + 0.64M NaHCO3 solution. Extensive conversion of the olivine to magnesite and amorphous silica was observed, confirming the viability of the new workflow and functionality of the designed reactor. Montney and Duvernay samples were then tested at 150°C/150bar in synthetic reservoir brine. Both samples underwent extensive dissolution with minor precipitation of secondary phases. Most of the precipitation occurred as an artifact of depressurization post experiment, where the Montney precipitated hematite and the Duvernay precipitated calcite. A second Montney test was conducted at 150°C/150bar in a 1M NaCl + 0.64M NaHCO3 solution to promote precipitation. In this test, precipitation of siderite occurred, but dissolution still dominated. As a result of these experiments, there appears to be limited potential for CO2 storage in the form of mineral trapping in the Montney and Duvernay reservoirs. However, the observed CO2 interactions have important implications for enhanced oil recovery in tight oil reservoirs hosted in the Montney and Duvernay formations.
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    Deformation of the Pacific Plate west of the Queen Charlotte Fault
    (2024-03-26) Perrin, Robert; Lauer, Rachel; Karchewski, Brandon; Pidlisecky, Adam; Tutolo, Benjamin; Innanen, Kristopher; Schaeffer, Andrew
    The Queen Charlotte Fault (QCF) is a transform fault that stretches from Haida Gwaii to Icy Point, Alaska, and has been of particular interest since an earthquake in 2012 demonstrated its geohazard potential. Observations made along the margin since then have raised questions about how deformation is distributed around the fault. Firstly, plate motion along the QCF is aligned with the fault apart from its southern section, where there is slight convergence between the Pacific and North American plates. While some evidence suggests the convergence may be accommodated by thickening of the Pacific Plate, there are uncertainties about how this is distributed along the QCF. Secondly, along the southern QCF lies the Queen Charlotte Terrace and several oblique faults. These features extend approximately 30 km west of the fault and are thought to be part of the mechanism that accommodates transpression along the southern QCF. This raises questions about why they are limited to this distance, and what the zone of influence of the fault might be. Finally, deformation of the Pacific Plate is controlled by lithospheric strength, which is a function of both thickness and temperature. Thick sediments west of the QCF, should allow young crust to be warmer than areas that are lightly sedimented. The limited heat flow observations that exist along the QCF, however, show a heat flow deficit, suggesting the crust may be cooler than expected. This raises questions about the thermal state of the crust, and how that may impact crustal deformation. This study examines these observations using several existing geophysical datasets. This study shows that the crust appears to be thicker than typical oceanic crust along Haida Gwaii. I also show that the zone of influence of the QCF is related to the dominant geometrical wavelengths of the fault and is consistent with observed deformation. Finally, I examine the thermal state of the crust to show that crustal cooling by hydrothermal circulation is likely occurring. The conclusions from this study improve our understanding of deformation of the Pacific Plate and underscore the need for continued studies along the QCF.
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    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.
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    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.
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    Geochemical evaluation of glauconite carbonation during sedimentary diagenesis
    (Elsevier, 2021-05-25) Zhang, Qin; Tutolo, Benjamin
    Glauconite is an authigenic, iron-rich clay mineral that is abundant in greensands formations worldwide. Evidence from these formations suggests that glauconite is commonly diagenetically converted to carbonate minerals such as siderite, ankerite, and ferroan dolomite. This process represents a natural CO2 sink that may provide an e ective mechanism for the engineered mineralization of anthropogenic CO2. To evaluate glauconite carbonation reactions and improve our understanding of glauconite diagenesis, we performed a detailed evaluation of the mechanisms through which carbonate minerals naturally replace glauconite during diagenesis of glauconitic sandstones from the Lower Cretaceous Upper Mannville Group in western Alberta, Canada. Using a combination of optical microscopy and scanning electron imaging, electron microprobe and bulk geochemical analyses, and x-ray fluorescence mapping, we show glauconite carbonation in the Mannville group is an reduction-facilitated, coupled glauconite recrystallization and siderite precipitation reaction. X-ray absorption near-edge spectroscopic mapping and spot analyses demonstrate that this reaction is accompanied by a significant shift in the oxidation state of Fe, from dominantly oxidized in glauconite to reduced in carbonate reaction products. Together, 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 sandstones. Results of thermodynamic models illustrate that, although K-feldspar is favored to precipitate during reductive glauconite dissolution and accompanying Fe-carbonate precipitation, its precipitation is likely kinetically limited, and that an Fe-impoverished glauconite is expected to recrystallize instead. Our findings show that glauconite carbonation is likely a common phenomenon in the subsurface, and thus that glauconite is potentially a significant cation source for mineralizing anthropogenic CO2.
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    An Investigation of Multicomponent Gas Flow in Tight and Shale Reservoirs
    (2023-01-06) Azni, Ahmad Shazryz; Kantzas, Apostolos; Tutolo, Benjamin; Aguilera, Roberto; Hassanzadeh, Hassan
    The complex gas dynamics in tight and shale reservoirs have become an important research topic in the oil and gas industry. This study proposes a steady-state flow test using adsorbing and non-adsorbing gases of single and binary gas components through tight adsorbing and non-adsorbing cores to investigate the true permeability value of its diffusion and slip counterparts. A steady-state flow permeability test was chosen to capture the complex gas dynamics in nanopore throats and the presence of organic matter. 1-D experiments in adsorbing (shale) and non-adsorbing (sandstone) cores are conducted under high overburden pressure at room temperature. The pressure difference and gas flow rates across the cores are measured. Helium (base case) is flowed, followed by adsorbing gases (N2 and CH4). This is followed by flowing gas mixtures to verify whether the single component values can be used in multicomponent systems. The results are compared to existing theoretical and analytical models. The apparent gas permeability for shale and sandstone decreases as the gas changes from non-adsorbing to adsorbing. This observation is not in line with the proposed hypothesis of the current models, where the flow mechanisms in tight and shale formations are treated like parallel resistors, where the total permeability is the addition of each component. The adsorbing gas significantly influences gas permeability when comparing the Klinkenberg plots for single and binary gas. The binary gas permeabilities skewed heavily to the gas with higher adsorbing capacity. Besides that, the adsorbing gas permanently changes the shale pore throat morphology by decreasing the pore radius, which significantly affects the flow mechanisms in shale. The study centred on the dissection of the flow mechanisms (viscous flow, surface diffusion, and Knudsen diffusion) contributing to the permeability calculations. Viscous flow dominates the more permeable porous media, while Knudsen diffusion is in the shale. Besides that, the binary gas mixture in a standard steady-state flow test in permeability estimation is introduced. The binary gas mixture in permeability measurement introduces the effect of gas flooding on the measured permeability. The more adsorbing gas actively displaces the less adsorbing gas and contributes to the surface diffusion permeability.
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    Iron oxidation and porosity generation in serpentinized abyssal peridotite
    (Elsevier, 2024-06-21) Pujatti, Simone; Sevgen, Serhat; Phelps, Patrick; Tutolo, Benjamin
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    Mineralogical characterization and thermodynamic modelling of scales formed in once through steam generators
    (Elsevier, 2022-01-15) Klyukin, Yury I.; Nightingale, Michael; Perdicakis, Basil; Mayer, Bernhard; Tutolo, Benjamin
    Extraction of hydrocarbons from oil sand deposits relies on technologies designed to lower bitumen viscosity, either by thermal energy or combination of thermal energy and solvents. Thermal energy is commonly delivered by steam. Once-through steam generators (OTSGs) are the most common class of generators used to generate steam from boiler feed water (BFW) at high pressure and temperature. Generated steam is used to mobilize the bitumen in the in situ reservoirs, and then water-bitumen emulsion is produced and processed, separating a hydrocarbon product and oil-free water, which subsequently will be reused to generate steam after treatment. Some of the aqueous constituents remaining or added during steam interaction with oil sands and subsequent treatment contribute to scale growth in OTSG tubing. Accumulation of the scale in OTSGs may lead to tubing failure due to overheating. In the present work we focused on inorganic scales – solid phases formed by components dissolved in BFW. We used a suite of geochemical, mineralogical and modelling techniques to characterize and model the inorganic components of scale samples provided by Canada's Oil Sands Innovation Alliance (COSIA) from OTSGs operators at multiple sites in Northeastern Alberta, Canada. We identified the composition of minerals in the scales as Na-, Ca-, and Mg-silicates with relatively low SiO44- content (inosilicates). Our modelling results allowed us to constrain the evolution of pressure, temperature, pH, mineral phases, and dissolved components in BFW as it undergoes heating in the OTSG to form steam and boiler-blowdown water. Modelling results are consistent with observed minerals and are promising for future management of scale formation processes.
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    Mineralogical characterization and thermodynamic modelling of scales formed in once through steam generators
    (Elsevier, 2021-09) Klyukin, Yury I.; Nightingale, Michael; Perdicakis, Basil; Mayer, Bernhard; Tutolo, Benjamin
    Extraction of hydrocarbons from oil sand deposits relies on technologies designed to lower bitumen viscosity, either by thermal energy or combination of thermal energy and solvents. Thermal energy is commonly delivered by steam. Once-through steam generators (OTSGs) are the most common class of generators used to generate steam from boiler feed water (BFW) at high pressure and temperature. Generated steam is used to mobilize the bitumen in the in situ reservoirs, and then water-bitumen emulsion is produced and processed, separating a hydrocarbon product and oil-free water, which subsequently will be reused to generate steam after treatment. Some of the aqueous constituents remaining or added during steam interaction with oil sands and subsequent treatment contribute to scale growth in OTSG tubing. Accumulation of the scale in OTSGs may lead to tubing failure due to overheating. In the present work we focused on inorganic scales – solid phases formed by components dissolved in BFW. We used a suite of geochemical, mineralogical and modelling techniques to characterize and model the inorganic components of scale samples provided by Canada's Oil Sands Innovation Alliance (COSIA) from OTSGs operators at multiple sites in Northeastern Alberta, Canada. We identified the composition of minerals in the scales as Na-, Ca-, and Mg-silicates with relatively low SiO44- content (inosilicates). Our modelling results allowed us to constrain the evolution of pressure, temperature, pH, mineral phases, and dissolved components in BFW as it undergoes heating in the OTSG to form steam and boiler-blowdown water. Modelling results are consistent with observed minerals and are promising for future management of scale formation processes.
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    Probing the application of kinetic theory to Mg-phyllosilicate growth with Si isotope doping
    (2021-04-29) Che, Zhengqiang; Tutolo, Benjamin; Tutolo, Benjamin; Mayer, Bernhard; Wieser, Michael
    The Principle of Detailed Balance (PDB) played a defining role in the derivation of the widely-used Transition State Theory rate law equation and serves as an important link between geochemical kinetics and thermodynamics. Although significant improvements have been made in applying the PDB to comparatively simple systems (e.g., SiO2-water), experimental verification of the PDB is lacking for more complex minerals such as the phyllosilicates. Among them, Mg-phyllosilicates are particularly important and have profound implications for the construction of facies models, element cycling in the lacustrine/marine realm, and interpretation of paleo-biogeochemistry. Here, we use 29Si isotopic doping techniques to quantify the rates of reaction between Mg-phyllosilicate substrates (amorphous Mg-silicate (a talc-like phase) and crystalline talc) and supersaturated solutions. The results show that the ratio of the forward and backward rates of amorphous Mg-silicate-water reaction approaches unity as the saturation state of the solution approaches the apparent solubility of amorphous Mg-silicate. The precipitation rates coupled with equivalent dissolution rates (in experiments with amorphous Mg-silicate substrates) appear to obey the same rate function as the precipitation rates coupled with negligible dissolution rates (in experiments with crystalline Mg-silicate substrates) over the degrees of supersaturation we explore, suggesting that the elementary step limiting the rate of precipitation remains the same. Accordingly, our results demonstrate that the PDB is applicable to amorphous Mg-phyllosilicate-water reactions, thereby reinforcing the use of TST rate equations to describe Mg-phyllosilicates growth. The experimental data can also be taken as evidence that the apparent solubility of amorphous Mg-silicate, a concept previously explained using the kinetic theory of nucleation and growth, also has a thermodynamic meaning, in that it represents a metastable equilibrium with the poorly crystalline phase. The measured, non-negligible forward and backward rates suggest that, even in this metastable state where little if any net reaction is occurring, isotopic signatures can be reset. Moreover, the significant discrepancy between the heterogeneous net growth rates on the amorphous Mg-silicate substrate versus those measured on crystalline talc and sepiolite substrates indicates that mineral crystallinity likely plays a key role in mineral growth during diagenesis.
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    Stochastic and deterministic groundwater modeling of a heterogeneous aquifer
    (2018-01-29) Niazi, Amir; Bentley, Laurence R.; Gloaguen, Erwan; Cey, Edwin; Tutolo, Benjamin; Hayashi, Masaki; Jensen, Jerry L.
    Groundwater models estimate head and fluxes into and out of an aquifer. They are the most important tools that we have, to predict aquifer response to natural and human-induced stresses; this makes them an inevitable part of any resource and environmental management study. Developing groundwater model is not always a straightforward task. It is especially challenging in heterogeneous and complex aquifers. Paskapoo Formation is a significant bedrock aquifer in Alberta, Canada. This heterogeneous aquifer is comprised mainly of relatively permeable sandstone embedded in relatively low permeable shale. There are several challenges in developing groundwater model in such formations including estimating groundwater recharge and characterizing heterogeneity. Groundwater recharge replenishes aquifers. Estimating spatial distribution of recharge is essential for water supply as well as contamination studies. A new method for estimating the spatial distribution of recharge is presented in this thesis. The method uses a combination of the baseflow method and the chloride mass balance method. In the method, total recharge over the entire watershed is estimated using the baseflow method, and then the spatial variability of recharge is approximated using groundwater chloride concentration. It will be shown that the proposed method does not need an estimation of the atmospheric deposition rate of chloride as long as the groundwater contribution to baseflow is estimated with a high degree of confidence. The efficacy of the method is demonstrated using data from a rural watershed in Alberta, Canada using a groundwater model. I showed that the difference between measured and modeled heads in the model that was calibrated using the spatially distributed recharge was lower than the model that was calibrated applying uniform recharge. Sufficient deterministic data are not usually available to map the heterogeneity of aquifers. Therefore, geostatistical simulations are utilized to build probable geological models of aquifers. I presented a Markov chain method to generate and condition a suite of stochastic representations (hereafter geomodels) of a highly heterogeneous and non-stationary fluvial bedrock aquifer using all available information, including paleo-current statistics, the proportion of each rock category, and lithologs. I also evaluated the capability of a well-known upscaling algorithm to estimate the effective hydraulic conductivity of the generated geomodels. Our numerical experiment showed that the upscaled hydraulic conductivity could not adequately capture the complex behaviours of the formation. In addition, we introduced a novel approach to condition geostatistical simulations of Paskapoo Formation using hydraulic data. The method creates a local geomodel that honors both the lithologic model and pumping test data. The proposed method uses probability perturbation method to locally search through an ensemble of possible geomodels which are generated using a random function, Transition Probability Markov-Chain, and conditioned by lithological data. Then the method rejects the geomodels which fail to reproduce the pumping test drawdown data. Consequently, the additional conditioning data (pumping test data) reduce the uncertainty space of the stochastic geomodel.
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    Stratigraphy and Sedimentology of Lower Permian Carbonates from Low-Latitude Tethys and Panthalassa Oceans
    (2023-12-20) Calvo Gonzalez, Daniel; Beauchamp, Benoit; Henderson, Charles; Tutolo, Benjamin; Angiolini, Lucia; Dutchak, Alexander; Hubbard, Stephen
    The Early Permian (Asselian–Kungurian) witnessed the peak and demise of the main phase of the late Paleozoic ice age (LPIA). This icehouse-greenhouse transition was concomitant to rising pCO2atm from pre-industrial levels in the earliest Asselian to modern-day values in the Sakmarian–Artinskian boundary before doubling today’s concentrations at the end of the Kungurian. This icehouse-greenhouse transition, considered one of the critical transitions affecting Earth prior to the latest Permian extinction, is viewed as a potential analogue to the icehouse-greenhouse shift predicted to occur if current pCO2atm continues to increase. Thus, the overarching goal of this study is to analyze the end of the LPIA as a potential analogue to an ever more likely future icehouse to greenhouse transition. In particular, this project is focussed on how low-latitude carbonate systems were impacted by the end of the LPIA. The Lower Permian carbonate-dominated successions in New Mexico, Austria, and South China record the peak and demise of the main phase of the LPIA. Asselian strata are arranged in transgressive-regressive sequences known as parasequences or cyclothems formed during this glacial interval. Sakmarian-Kungurian strata comprise non-cyclic deposits formed after glaciation. Cyclothems are widely interpreted as far-field records of glacioeustatic sea-level fluctuations mirroring the waxing and waning of ice sheets. However, the amplitude of glacioeustatic fluctuations represented in Paleozoic cyclothems remains unclear. Chapter 2 clarifies the amplitude of eustatic fluctuations represented in coeval cyclothems of the Robledo Mountains (New Mexico) and Carnic Alps (Austria) and proposes a stepwise demise of the main phase of the LPIA using microfacies analysis. Additionally, based on foraminifer and conodont biostratigraphy, the end of cyclic deposition is dated as Asselian–Sakmarian. Lastly, a sequence stratigraphic framework for the studied interval is established based on microfacies analysis and field observations. Contemporaneous to this glacial phase, an aridification and seasonality trend associated with intensifying low-latitude monsoonal circulation began across Pangea. In South China, a shift towards warm and humid conditions, known as the Artinskian Warming Event (AWE), had a profound impact on sedimentation of carbonate platforms adjacent to emerged areas. Enhanced coastal upwelling driven by intensified monsoonal circulation affected sedimentation of platforms outboard. Based on microfacies analysis, Chapter 3 investigates how shelf carbonates in South China were affected by AWE and enhanced coastal upwelling and provides an updated age interpretation of the upper Maping and lower Chihsia formations in Laibin and Dahua (South China) combining foraminifer and conodont biostratigraphy. Additionally, a sequence stratigraphic framework was suggested for the studied interval based on microfacies analysis and field observations. Enhancement of coastal upwelling may have been common across low-latitude carbonate systems as monsoonal circulation intensified. Analyzed Artinskian successions in this study are dominated by photozoan assemblages punctuated by recurrent interbeds with a heterozoan assemblage. The abundance and frequency of these interbeds may indicate the effect of Milankovitch cycles (i.e., precession) in the intensification of coastal upwelling. Chapter 4 explains the occurrence of these high-frequency shifts in carbonate assemblages observed in coeval Artinskian successions of New Mexico, Austria, and South China.
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    The effects of water-rock interactions on the permeability of the Precambrian Basement in Southern Saskatchewan
    (2023-06-14) Smith, Taylor; Tutolo, Benjamin; Lauer, Rachel; Shor, Roman; Grasby, Stephen
    Geothermal energy has gained significance as a potential low-carbon, renewable energy source. Approximately 70% of the world’s geothermal reservoirs are defined as low temperature (<150°C), with the potential to power agricultural machinery, support direct heating of homes, buildings, and therapeutic facilities, and produce electricity using specialized facilities. The Precambrian basement underlying the Williston Basin in southern Saskatchewan, with a reservoir temperature of ~120°C, represents one such geothermal resource. Well tests and examination of recovered samples suggest that this, and other similar reservoirs globally, present suitable conditions for geothermal energy production. However, geochemically induced permeability alteration in these potentially highly reactive granitoid rocks presents a significant risk to sustained heat production from these low-temperature resources. To assess this risk, and potentially identify mitigation measures, we conducted a geochemical and mineralogical study of samples recovered from this reservoir. Mineral composition and thermal history of both altered and unaltered samples were quantified through a combination of petrographic, Raman Spectroscopy, and Electronic Microprobe analyses, and the resultant values were then utilized to parameterize geochemical simulations of water-rock interactions at relevant conditions. The simulations permitted prediction of mineral volume changes, and hence inferences about porosity and permeability changes, as a result of these interactions. The simulations suggest that mineral volume will increase as a result of water-rock interaction in both unaltered and altered zones of the basement rocks permeability, but that the geothermal alteration of the unaltered, and hence more reactive, rocks would yield mineral volume changes around 30% greater than the altered rock. Applying the porosity-permeability relationship equation developed by Verma and Pruess (1988), the calculated change in permeability indicates the unaltered Precambrian basement rock will experience a greater change in total permeability compared to the altered basement rocks. Additional calculations show that the Verma Pruess’s equation is sensitive to critical porosity and fitting parameter and predicts various scenarios resulting in a range of permeability change from 1x10-13 to 1x10-20 m2. Based on this result, we infer that altered, permeable zones of the Precambrian basement underlying the Williston basin are likely to provide conditions favorable for the sustained, multi-decade heat production that would be required to justify initial capital expenditures, and hence should be targeted over less altered zones. Geothermal heat extraction from permeable, altered zones of warm Precambrian granitoid rocks globally is an understudied but potentially fruitful resource to reliably produce low-carbon, renewable energy as we seek to decarbonize the global economy.