Browsing by Author "Nightingale, Michael"
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- ItemOpen AccessThe 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.
- ItemOpen AccessIdentification of Geochemical Processes During Hydraulic Fracturing of a Shale Gas Reservoir: A Controlled Field and Laboratory Water‐Rock Interaction Experiment(Wiley Subscription Services, Inc., 2020-10-28) Huang, Tianming; Li, Zhenbin; Mayer, Bernhard; Nightingale, Michael; Li, Xiao; Li, Guanfang; Long, Yin; Pang, ZhongheA detailed study on geochemical processes following hydraulic fracturing can provide important information on the origin of solutes and potential improvement of fracturing technology. However, this remains difficult due to the low resolution of flowback water and high salinity of formation water. To fill this knowledge gap, a shale-gas well was drilled and freshwater was used to fracture the shale. In parallel, laboratory water-rock interaction experiments were conducted. The intensive sampling for flowback water and the use of multiple isotopes provided novel and detailed insights into the water-rock interactions after hydraulic fracturing. The results showed that beyond mixing processes, cation exchange, adsorption/desorption, and barite precipitation were observed both in the laboratory and field studies. Although oxidation of pyrite was observed in most of the laboratory experiments, our findings demonstrate that this process was not evident in field flowback samples that were dominated by mixing of fracturing fluids and formation water.
- ItemOpen AccessMethane oxidation and methylotroph population dynamics in groundwater mesocosms(Society for Applied Microbiology and John Wiley & Sons Ltd., 2020-01) Kuloyo, Olukayode; Ruff, S Emil; Cahill, Aaron; Connors, Liam; Zorz, Jackie K; Hrabe de Angelis, Isabella; Nightingale, Michael; Mayer, Bernhard; Strous, MarcExtraction of natural gas from unconventional hydrocarbon reservoirs by hydraulic fracturing raises concerns about methane migration into groundwater. Microbial methane oxidation can be a significant methane sink. Here, we inoculated replicated, sand-packed, continuous mesocosms with groundwater from a field methane release experiment. The mesocosms experienced thirty-five weeks of dynamic methane, oxygen and nitrate concentrations. We determined concentrations and stable isotope signatures of methane, carbon dioxide and nitrate and monitored microbial community composition of suspended and attached biomass. Methane oxidation was strictly dependent on oxygen availability and led to enrichment of 13 C in residual methane. Nitrate did not enhance methane oxidation under oxygen limitation. Methylotrophs persisted for weeks in the absence of methane, making them a powerful marker for active as well as past methane leaks. Thirty-nine distinct populations of methylotrophic bacteria were observed. Methylotrophs mainly occurred attached to sediment particles. Abundances of methanotrophs and other methylotrophs were roughly similar across all samples, pointing at transfer of metabolites from the former to the latter. Two populations of Gracilibacteria (Candidate Phyla Radiation) displayed successive blooms, potentially triggered by a period of methane famine. This study will guide interpretation of future field studies and provides increased understanding of methylotroph ecophysiology.
- ItemOpen AccessMineralogical 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, BenjaminExtraction 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.
- ItemOpen AccessMineralogical 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, BenjaminExtraction 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.
- ItemOpen AccessMolecular and stable carbon isotope geochemistry of mud-gas-derived hydrocarbons and its application for the assessment of low-permeability reservoirs from the Montney Formation, Western Canada(Elsevier, 2022-01-03) Cesar, Jaime; Mayer, Bernhard; Becker, Veith; Nightingale, Michael; Ardakani, Omid H.Mud-gas isotope logging (MGIL) of hydrocarbons (methane, ethane, propane) has become a widely used approach to fingerprint gas-bearing formations during the drilling of vertical and horizontal oil and gas wells often with the goal to assess potential cross-formational gas migration. In this study, we have used mud-gas molecular and isotope data to assess the usefulness of MGIL for the geochemical assessment of a single low-permeability reservoir formation, the Montney Formation in Western Canada. An example from a well completed in British Columbia shows that hydrocarbon samples collected in IsoJars® tend towards more positive carbon isotope ratios compared to data for samples obtained using IsoTubes®, potentially attributed to 13C enriched residual gas retained in the cuttings. Additionally, in publically available mud-gas data from 45 other wells, it was found that the carbon isotope ratios of mud-gas from the Montney Formation are overall consistent with the thermal maturity of this stratigraphic unit, but the data display a relatively scattered trend on a thermal maturity plot based on Δ13CC1-C2 and Δ13CC1-C3. Molecular parameters such as [C1/(C2 + C3)] can be modified via processes such as desorption and diffusion after sampling gases in IsoJars®, while the i-C4/n-C4 ratio was found to be the most consistent molecular parameter between sampling techniques. We conclude that mud-gas molecular and isotope data derived from samples collected in IsoTubes® are suitable for geochemical assessment (e.g. thermal maturity, fluid–fluid correlations) of low permeability hydrocarbon reservoirs such as the Montney Formation.
- ItemOpen AccessA Probabilistic Approach for Predicting Methane Occurrence in Groundwater(American Chemical Society, 2019-11-05) Humez, Pauline; Osselin, Florian; Wilson, Leah J; Nightingale, Michael; Kloppmann, Wolfram; Mayer, BernhardAqueous geochemistry datasets from regional groundwater monitoring programs can be a major asset for environmental baseline assessment (EBA) in regions with development of natural gases from unconventional hydrocarbon resources. However, they usually do not include crucial parameters for EBA in areas of shale gas development such as methane concentrations. A logistic regression (LR) model was developed to predict the probability of methane occurrence in aquifers in Alberta (Canada). The model was calibrated and tested using geochemistry data including methane concentrations from two groundwater monitoring programs. The LR model correctly predicts methane occurrence in 89.8% (n = 234 samples) and 88.1% (n = 532 samples) of groundwater samples from each monitoring program. Methane concentrations strongly depend on the occurrence of electron donors such as sulfate and to a lesser extent on well depth and the total dissolved solids of groundwater. The model was then applied to a province-wide public health groundwater monitoring program (n = 52,849 samples) providing aqueous geochemistry data but no methane concentrations. This approach allowed the prediction of methane occurrence in regions where no groundwater gas data are available, thereby increasing the resolution of EBA in areas of shale gas development by using basic hydrochemical parameters measured in high-density groundwater monitoring programs.
- ItemOpen AccessA rate law for sepiolite growth at ambient temperatures and its implications for early lacustrine diagenesis(2020-01) Arizaleta, Maria L.; Nightingale, Michael; Tutolo, Benjamin M.
- ItemOpen AccessRedox controls on methane formation, migration and fate in shallow aquifers(Copernicus Publications, 2016-07-12) Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Bayegnak, Guy; Millot, Romain; Kloppmann, WolframDevelopment of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish (a) natural in situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. This study combines aqueous and gas (dissolved and free) geochemical and isotope data from 372 groundwater samples obtained from 186 monitoring wells of the provincial Groundwater Observation Well Network (GOWN) in Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. We investigated whether methane occurring in shallow groundwater formed in situ, or whether it migrated into the shallow aquifers from elsewhere in the stratigraphic column. It was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of biogenic methane (> 0.01 mM or > 0.2 mgL−1), characterized by δ13CCH4 values < −55 ‰, occurred in anoxic Na-Cl, Na-HCO3, and Na-HCO3-Cl type groundwaters with negligible concentrations of nitrate and sulfate suggesting that methane was formed in situ under methanogenic conditions for 39.1 % of the samples. In only a few cases (3.7 %) was methane of biogenic origin found in more oxidizing shallow aquifer portions suggesting limited upward migration from deeper methanogenic aquifers. Of the samples, 14.1 % contained methane with δ13CCH4 values > −54 ‰, potentially suggesting a thermogenic origin, but aqueous and isotope geochemistry data revealed that the elevated δ13CCH4 values were caused by microbial oxidation of biogenic methane or post-sampling degradation of low CH4 content samples rather than migration of deep thermogenic gas. A significant number of samples (39.2 %) contained methane with predominantly biogenic C isotope ratios (δ13CCH4 < −55 ‰) accompanied by elevated concentrations of ethane and sometimes trace concentrations of propane. These gases, observed in 28.1 % of the samples, bearing both biogenic (δ13C) and thermogenic (presence of C3) characteristics, are most likely derived from shallow coal seams that are prevalent in the Cretaceous Horseshoe Canyon and neighboring formations in which some of the groundwater wells are completed. The remaining 3.7 % of samples were not assigned because of conflicting parameters in the data sets or between replicates samples. Hence, despite quite variable gas concentrations and a wide range of δ13CCH4 values in baseline groundwater samples, we found no conclusive evidence for deep thermogenic gas migration into shallow aquifers either naturally or via anthropogenically induced pathways in this baseline groundwater survey. This study shows that the combined interpretation of aqueous geochemistry data in concert with chemical and isotopic compositions of dissolved and/or free gas can yield unprecedented insights into formation and potential migration of methane in shallow groundwater. This enables the assessment of cross-formational methane migration and provides an understanding of alkane gas sources and pathways necessary for a stringent baseline definition in the context of current and future unconventional hydrocarbon exploration and exploitation.
- ItemOpen AccessStable carbon isotope systematics of methane, ethane and propane from low-permeability hydrocarbon reservoirs(Elsevier, 2020-10-10) Cesar, Jaime; Nightingale, Michael; Becker, Veith; Mayer, BernhardWe have reassessed the stable carbon isotope systematics of methane (C1), ethane (C2), and propane (C3) in more than 500 natural gas samples from low-permeability hydrocarbon reservoirs around the world, with the purpose of providing new tools for thermal maturity assessment of natural gas that is increasingly produced from such reservoir types world-wide. A low-permeability reservoir resembles a semi-closed system and we found that the stable carbon isotope distribution in C1-C3 alkanes differs partially from what has been previously observed in natural gas from conventional hydrocarbon accumulations (e.g. C isotope distributions dominated by Rayleigh distillation and kinetic isotope effects). In a low-permeability reservoir, isotope exchange may play a more prominant role in the carbon isotope distribution, driving the system towards an even isotopic distribution (EID) of 6‰ between methane and ethane, and ethane and propane, at Ro of 1.5%. At higher maturity, ethane and propane depleted in 13C are formed as a consequence of thermal cracking of wet-gas components and possibly free radical decomposition/polymerization reactions, which leads to the occurrence of isotope reversals (δ13CC2 < δ13CC1 < δ13CC3, δ13CC2 < δ13CC3 < δ13CC1 and δ13CC3 < δ13CC2 < δ13CC1) at thermal maturity higher than 2.0%Ro. The diagram of the isotopic differences ∆13CC1-C2 (δ13CC1-δ13CC2) versus ∆13CC1-C3 (δ13CC1-δ13CC3) provides a new tool for classification of natural gas from low-permeability hydrocarbon reservoirs according to thermal history in three main regions: normal trend (subdivided into immature, oil/wet-gas window, and dry gas window), ethane reversal, and propane reversal with respect to methane. This new tool can be used to assess the maturity of the petroleum fluids and can assist in identifying hydrocarbon mixing.
- ItemOpen AccessWater-co2-rock interactions at the Pembina cardium co2 monitoring pilot(2010) Nightingale, Michael; Mayer, Bernhard