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TitreHydrocarbon evaporative loss from shale core samples as revealed by Rock-Eval and thermal desorption-gas chromatography analysis: Its geochemical and geological implications
AuteurJiang, C; Chen, Z; Mort, A; Milovic, M
SourceMarine and Petroleum Geology vol. 70, 2015 p. 294-303, https://doi.org/10.1016/j.marpetgeo.2015.11.021
Année2015
Séries alt.Secteur des sciences de la Terre, Contribution externe 20150321
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.marpetgeo.2015.11.021
Mediapapier; en ligne; numérique
Formatspdf
Sujetsressources pétrolières; gaz d'hydrocarbure; géochimie des hydrocarbures; maturation des hydrocarbures; hydrocarbures légers; migration des hydrocarbures; analyses de carbone organique; schiste, derive; schistes bitumineux; géologie économique; géochimie; sédimentologie; combustibles fossiles; Dévonien; Ordovicien
Illustrationstables; graphs; geochemical charts
ProgrammeÉvaluation des ressources pétrolières pour les schistes, Les géosciences pour les nouvelles sources d'énergie
Résumé(disponible en anglais seulement)
The S1 peaks generated by Rock-Eval analysis of source rock and reservoir interval core and cuttings samples have been routinely employed for in-place hydrocarbon resources assessment by petroleum geochemists, geologists and even engineers. Due to the evaporative loss of gaseous and light hydrocarbons during core and cuttings collection and storage as well as sample preparation in the laboratory before instrumental analysis, a correction to the S1 values is needed in order to obtain a more accurate estimate of the resources. To investigate the effect of evaporative loss on both the amount and the composition of the hydrocarbons retained in shale, a time-series of Rock-Eval and thermal desorption-gas chromatography (TD-GC) analyses have been carried out on an organic-rich Duvernay Formation shale core sample from the Western Canada Sedimentary Basin (WCSB) and an organic-lean Lorraine Formation shale core sample from Quebec, Canada. The results suggest that the content of total organic carbon (TOC) may play an important role in preserving hydrocarbons in sedimentary rocks. A total loss of gaseous and light liquid hydrocarbons up to C9 is shown to take place within 21 hours of sample preparation for the low TOC (<1%) Ordovician Lorraine shale when the powdered sample was left exposed to the open air, accounting for a 38% decrease in its Rock-Eval S1 peak. The Rock-Eval S1 peak can be reduced by 29% even if the powdered sample has been stored in a sealed container for just over a week. In contrast, the volatile loss has been found to be at a much slower rate for the high TOC (> 11%) Devonian Duvernay shale core sample. After 360 hours of exposure to the open air, the powdered Duvernay shale sample shows only 15% decline in its Rock-Eval S1 peak, and still contains high relative concentrations of C7?C9 hydrocarbons. In addition, the evaporative loss of some isomers of C5?C7 hydrocarbons from the organic-rich shale is not fully in agreement with their GC retention/elution behavior, but appears to be partially controlled by their adsorption/desorption process on the organic matter and mineral matrix as well. This suggests that the C5-C8 gasoline range light hydrocarbon parameters should be used with caution for oil-oil correlation for unconventional shale and tight petroleum systems. While the findings in this work validate the current industrial practice that targets organic-rich and mature shale intervals for unconventional shale gas and oil exploration because of their large hydrocarbon storage capacity, the study also has an important implication that high TOC content may adversely affect the production efficiency of shale and tight hydrocarbon reservoirs due to the strong adsorption of hydrocarbons by the high maturity organic matter.
Résumé(Résumé en langage clair et simple, non publié)
Les pics S1 générés par l'analyse Rock-Eval d'échantillons de roches mères et de réservoirs ont été systématiquement utilisés pour l'évaluation des ressources en hydrocarbures par des géologues pétroliers et ingénieurs. En raison de la perte par évaporation d'hydrocarbures volatils lors de la collecte de l'échantillon, son entreposage stockage et lors de la préparation avant l'analyse instrumentale, une correction des valeurs S1 est nécessaire afin d'obtenir une estimation plus précise des ressources. En plus du Rock-Eval, des analyses de chromatographie par désorption thermique à gaz (TD-GC) ont également été effectuées sur des échantillons de carottes de schiste des bassins de l'Alberta et du Québec et ce à différents moments après la préparation d'échantillons pour étudier l'effet de la perte des volatiles. Les résultats indiquent que la matière organique dans le schiste peut aider à retenir les hydrocarbures en particulier les composants volatiles par adsorption, empêchant ainsi leur perte par évaporation.
GEOSCAN ID297380