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TitreDetermination of hydrocarbon generation and expulsion temperature of organic-rich Upper Ordovician shales from Hudson Bay and Foxe basins using modified hydrous pyrolysis, organic petrography, Rock-Eval analysis and organic solvent extraction
TéléchargerTéléchargements
AuteurReyes, J; Jiang, C; Lavoie, D; Milovic, M; Robinson, R; Zhang, S; Armstrong, D; Mort, A
SourceCommission géologique du Canada, Dossier public 8049, 2016, 60 pages, https://doi.org/10.4095/299254
Année2016
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/299254
Mediaen ligne; numérique
Formatspdf
ProvinceRégion extracotière du nord; Ontario; Nunavut
SNRC43; 44; 45; 54; 55; 25; 35; 36; 46
Lat/Long OENS -94.0000 -68.0000 66.0000 50.0000
Sujetsanalyses géochimiques; analyses pétrographiques; mudstones; schistes; roches mères; réflectance de la vitrinite; bitume; hydrocarbures; production d'hydrocarbure; géochimie; combustibles fossiles; Ordovicien
ProgrammeRoches mères des hydrocarbures de la région d'Hudson/Ungava, GEM2 : La géocartographie de l'énergie et des minéraux
Diffusé2016 11 02
Résumé(Sommaire disponible en anglais seulement)
Immature organic-rich Ordovician mudstone and limy shale source rocks were artificially matured using modified hydrous pyrolysis in an attempt to characterize the thermal maturation history and hydrocarbon generation scenario. The experimental hydrous pyrolysis temperature range of 310-350 oC for 72 hours corresponds to hydrocarbon generation (HCG) at laboratory timescales. The Rock-Eval (RE) results show that the Tmax of the pyrolyzed samples increased from 413 oC to 450 oC after the last stage (350 oC) of hydrous pyrolysis. Solvent extraction and RE analysis of pyrolyzed rock chips indicates that Tmax suppression is associated with the high amount of free hydrocarbons and soluble solid bitumen or extractable organic matter in the samples.
The estimated vitrinite reflectance equivalent values calculated from the measured Tmax (0.67 to 1.03 %Roeqv-ext), chitinozoan (0.68 to 1.1 %Roeqv) and bitumen (0.75 to 1.08 %Roeqv) reflectance are in excellent agreement and indicate that all artificially matured samples reached HCG at 310°C. Organic petrographic analysis of the pyrolyzed rock chips from hydrous pyrolysis shows that bituminite and other amorphous kerogen are the first macerals to thermally degrade, followed by prasinophyte alginite. Some of the pore spaces created by the thermally degraded amorphous kerogen and bituminite are partially filled by soluble heavy bitumen. The solubility of the solid bitumen and the amount of free hydrocarbons decreases, and the fluorescence intensity of liptinite macerals shifts from bright yellow to reddish orange with increasing pyrolysis temperature. Free hydrocarbons in fracture and intergranular pore spaces were also observed in the rock matrix after hydrous pyrolysis.
Peak hydrocarbon generation occurs between pyrolysis temperatures of 330 and 350 oC with measured Tmax values of 439 to 455 oC after solvent extraction. The quantity of generated hydrocarbons ranges from 22.75 to 166.22 mg HC/g TOC. Comparisons of the calculated TRs of HI and S2 from unextracted and extracted pyrolyzed rock chips clearly indicate that the unextracted samples underestimate the residual hydrocarbon potential of the pyrolyzed source rocks. The underestimation appears to be higher during the formation of heavy oil and soluble bitumen, which declines exponentially as the pyrolysis temperature increases.
Comparative analysis of the geochemical data from the offshore wells from the Hudson Bay Basin and the results of this study suggest that the observed large Tmax variation among the samples from the offshore wells cannot be attributed to Tmax suppression associated with a high amount of soluble organic matter and labile hydrocarbons. Almost all of the RE parameters show no indication of in-situ oil generation and migration. Petrographically, none of these previously analyzed offshore Upper Ordovician formations showed any direct evidence of in-situ hydrocarbon generation and migration unlike those observed in the artificially matured samples. If indeed the measured and estimated Tmax values (>435 oC) are the effective maximum and current burial temperatures of these organic rich formations, migrated solid bitumen and free hydrocarbon will be visible within the intergranular pore spaces of the rock matrix at this level of thermal maturity.
Résumé(Résumé en langage clair et simple, non publié)
Quatre mudstones et shales calcareux, immatures et riches en matière organique provenant de roche-mères à hydrocarbures des bassins de la Baie d'Hudson et de Foxe du nord du Canada furent cuits artificiellement en utilisant la méthode modifiée de pyrolyse aqueuse. Cette étude visait à déterminer la maturation thermique, les phases et cinétiques de génération des hydrocarbures. Les températures de pyrolyse sur 72 heures furent de 310, 320, 330, 340 et 350°C; ces températures correspondent à la fenêtre à l'huile. Les analyses de géochimie et de pétrographie organique avant et après chaque étape de la pyrolyse suggèrent que tous les échantillons ont atteint le stage de génération d'hydrocarbures basé sur les mesures de Tmax et de l'équivalent vitrinite de la réflectance. Des hydrocarbures furent expulsées après 310 et 320°C; le maximum du taux d'expulsion fut atteint après les températures de pyrolyse de 330 et 350°C. Les taux d'expulsion varient selon les formations entre 22.75 et 166.22 mg HC/g COT. Le ratio de transformation (RT) de l'indice d'hydrogène est entre 22 à 82% et de 47 à 92% pour S2.
GEOSCAN ID299254