| Title | Synthesis of organic matter composition and maturation and gas data from selected deep source rock units for some wells in the Fox Creek area |
| Download | Downloads |
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| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Lavoie, D ;
Ardakani, O H; Rivard, C |
| Source | Geological Survey of Canada, Open File 8788, 2021, 95 pages, https://doi.org/10.4095/328238  Open Access |
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| Year | 2021 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Alberta |
| NTS | 83F |
| Area | Fox Creek |
| Lat/Long WENS | -118.0000 -116.0000 54.0000 53.0000 |
| Subjects | hydrogeology; environmental geology; fossil fuels; Economics and Industry; Nature and Environment; Science and Technology; groundwater resources; aquifers; groundwater pollution; petroleum industry;
petroleum exploration; hydrocarbons; gas; oil; coal; thermal maturation; isotopic studies; carbon isotopes; pyrolysis; source rocks; petrographic analyses; depositional environment; reflectance; vitrinite reflectance; temperature; wells; bedrock
geology; lithology; sedimentary rocks; sandstones; conglomerates; limestones; dolostones; carbonates; clastics; evaporites; shales; siltstones; mudstones; Paleogene; Paleocene; Western Canada Sedimentary Basin; Duvernay Formation; Montney Formation;
Fernie Formation; Nordegg Member; Mannville Group; Paskapoo Formation; Methodology; Environmental impact assessment; cumulative effects; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous; Jurassic; Triassic; Paleozoic; Devonian |
| Illustrations | stratigraphic charts; diagrams; photomicrographs; tables; location maps; plots; profiles |
| Program | Environmental Geoscience Potential impacts of oil and gas development on non-saline aquifers, Fox Creek |
| Released | 2021 04 28 |
| Abstract | An analysis of historical and new organic matter data, as well as gas composition and isotopic ratios for deep hydrocarbon source rocks, is part of a holistic study of the potential environmental impact
of unconventional hydrocarbon development in the Fox Creek area in Alberta. The goal of this activity is to use thermal maturation and gas data from deep source rocks to generate a database for the interpretation of source rocks for eventual
dissolved hydrocarbons in shallow groundwater.
The organic matter study consists of new petrographic observations on pellets from the Duvernay, Montney, Nordegg, and Mannville organic-rich samples. The petrography indicates that the organic matter
is of marine Type II origin with one coal (Type III) sample in the Mannville Group. The organic matter reflectance measurements were taken on bitumen and converted to equivalent vitrinite reflectance values; vitrinite reflectance has been directly
measured from the coal sample. The data indicate that all units reached thermal conditions for the production of hydrocarbons. The deep Duvernay Formation has the highest thermal maturity data that suggest the end of the oil window in the eastern end
of the study area and the onset of the condensate zone in the western part of the study area.
Rock-Eval data from publicly available wells in the GSC database were evaluated for the Duvernay, Montney, and Nordegg units. The Tmax values indicate
that these units are within the hydrocarbon production zones. As with the vitrinite-equivalent data, the Duvernay Formation has reached the highest thermal maturity in the study area with values indicative of the condensate zone, the other units
belong to the oil zone.
Gas samples were collected in isotubes at the time of drilling. Samples were collected at various depths with some wells having only a short interval with data, while others have samples from a much longer interval. Data
from 7 wells were available for our study, 6 of the wells are located at the eastern end of the study area while the last one is much further north. From gas composition (wetness ratio: C1/(C2+C3)) and delta-13C ratios of methane, the origin of the
gas is thermogenic. The vertical trends of delta-13C ratios of ethane versus depth and wetness, as well as butane ratios (iC4/nC4) versus depth and wetness for wells with a longer distribution of samples, suggest partial isotopic rollover. The
roll-over was not fully developed as nowhere do we see delta-13C ratios of ethane being lighter (more negative) than that delta-13C ratio of methane. This suggests, as supported by the organic matter reflectance and Rock-Eval data, that the study
area never reached very high thermal conditions. The fact that significant statistical overlap of delta-13C ratios of methane and the inverted trend of delta-13C ratios for ethane challenges the use of these isotopes data for source interpretation of
eventual dissolved hydrocarbons in groundwater. However, some limited data for the shallowest sampling intervals (<1500 m) in some wells suggest that more significantly different data might be present in shallower sections in the subsurface. Data
from eventual shallow coals intercepted by monitoring wells to be drilled are considered critical for the interpretation of the source for eventual dissolved hydrocarbons in groundwater. |
| Summary | (Plain Language Summary, not published)
An analysis of historical and new organic matter data, as well as gas composition and isotopic ratios for deep hydrocarbon source rocks, is part of a
holistic study of potential environmental impact of unconventional hydrocarbon development in the Fox Creek area in Alberta. The goal of this activity is to use thermal maturation and gas data from deep source rocks to generate a database for the
interpretation of source rocks for eventual dissolved hydrocarbons in shallow groundwater. |
| GEOSCAN ID | 328238 |
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