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TitleOrganic petrographic analysis of artificially matured chitinozoan- and graptolite-rich Upper Ordovician shale from Hudson Bay Basin, Canada
AuthorReyes, JORCID logo; Jiang, CORCID logo; Lavoie, DORCID logo; Armstrong, D K; Milovic, M; Robinson, R
SourceInternational Journal of Coal Geology vol. 199, 2018 p. 138-151,
Alt SeriesNatural Resources Canada, Contribution Series 20180057
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNunavut; Ontario; Manitoba
NTS25N; 32M; 33D; 33E; 33L; 33M; 33N; 34C; 34F; 34K; 34L; 34M; 34N; 35C; 35D; 35E; 35F; 35K; 35M; 35N; 42I; 42J; 42K; 42L; 42M; 42N; 42O; 42P; 43; 53H; 53I; 53J; 53K; 53N; 53O; 53P; 54A; 54B; 54C; 54F; 54K
AreaHudson Bay; Southampton Island; Hudson Strait; Baffin Island; Foxe Basin; James Bay
Lat/Long WENS -96.0000 -63.0000 66.0000 48.0000
Subjectsfossil fuels; geochemistry; paleontology; Upper Ordovician; bedrock geology; lithology; sedimentary rocks; shales; mudstones; petrographic analyses; fossils; organic geochemistry; pyrolysis; thermal maturation; hydrocarbon generation; source rocks; petroleum resources; vitrinite reflectance; bitumen; kerogen; maceral analyses; fluorescence analyses; Hudson Bay Basin; Chitinozoans; Graptolites; Cape Henrietta Maria Arch; Boas River Formation; Asheweig River Formation; Boothia-Bell Arch; Moose River Basin; Phanerozoic; Paleozoic; Ordovician
Illustrationsgeoscientific sketch maps; tables; photomicrographs; bar graphs; cross-plots
ProgramGEM2: Geo-mapping for Energy and Minerals Hudson/Ungava Hydrocarbon source rocks
Released2018 10 03
AbstractChitinozoan, graptolite and organic-rich immature Upper Ordovician mudstone was artificially matured using closed hydrous pyrolysis. The pyrolysis was performed at isothermal temperatures of 310-350 °C at 10 °C increments for 72 h. This temperature range simulates the subsurface thermogenic hydrocarbon generation window based on previous laboratory simulations. The objectives of this study are to (a) qualitatively and quantitatively assess the degree of physicochemical transformation of dispersed organic matter (DOM) and zooclasts in BRF petroleum source rock after artificial maturation; and (b) determine the relationship between graptolite, chitinozoan, vitrinite-like particle and bitumen reflectance (Ro) with increasing pyrolysis temperature and the thermal maturity. Petrographic analysis shows that bituminite and amorphous kerogen were the first organic macerals to thermally decompose after the first pyrolysis temperature. This is followed by liptodetrinite, thin-walled alginite, acritarch, and telalginite as pyrolysis temperature increases. Concurrently, the fluorescence properties of the telalginite shifted from greenish yellow to reddish-orange after the last stage (350 °C) pyrolysis. In addition, significant amount of bright fluorescing labile hydrocarbons produced during pyrolysis were observed oozing from pore spaces and on the surface of the rock matrix. Pore-filling, orange to reddish-orange fluorescing solid bitumen were also found in pores spaces created by the thermal decomposition of DOM. The lack of morphological evidence for the thermal decomposition of chitinozoans and graptolites suggests that these zooclasts macerals may have limited or have no contribution to the overall hydrocarbon generation. Nonetheless, their respective reflectance (Ro) increased (0.64% to 1.34% and 0.55% to 1.38%) as the pyrolysis temperature was increased. These Ro values are significantly higher than the vitrinite-like particles (0.49% to 1.07%) and solid bitumen (0.30% to 1.09%). The measured RocK-Eval Tmax and solid bitumen vitrinite reflectance equivalent (VRo-eqv) are comparable to the average vitrinite-like particles. The relationship between rate of increase in chitinozoan and graptolite, and vitrinite-like particles Ro, expressed by the equations: Ro-vit-like=0.77 Rchi and Ro-vit-like=0.79 Rgrap, are comparable to those observed in geologically matured source rocks.
Summary(Plain Language Summary, not published)
This manuscript discusses the results of the artificially maturation of immature chitinozoan and organic-rich Upper Ordovician potential source rocks from Boas River Formation shale using closed hydrous pyrolysis. The results of qualitatively and quantitatively analyses using bulk geochemical (Rock-Eval) and organic petrography shows the gradual physical and chemical changes in the organic matter composition as they thermally decomposed in response to increasing pyrolysis temperature. The significant amount of oil and bitumen produced from the thermal decomposition of organic matter provides evidence for artificial maturation and hydrocarbon generation. Other key thermal maturity indicator like the Tmax, vitrinite and zooclast reflectance also indicates that this potential source rock was successfully matured.

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