| Title | Numerical modeling of hydrocarbon generation in the Douglas Formation of the Athabasca Basin (Canada) and implications for unconformity-related uranium mineralization |
| Author | Chi, G; Li, Z; Bethune, K |
| Source | Journal of Geochemical Exploration vol. 144, pt. A, 2014 p. 37-48, https://doi.org/10.1016/j.gexplo.2013.10.015 |
| Year | 2014 |
| Alt Series | Earth Sciences Sector, Contribution Series 20130328 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf; html |
| Province | Saskatchewan |
| NTS | 64E; 64L; 64M; 74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P |
| Area | northern Saskatchewan |
| Lat/Long WENS | -112.0000 -102.0000 60.0000 57.0000 |
| Subjects | geochemistry; fossil fuels; economic geology; models; modelling; uranium; mineralization; mineral occurrences; mineral deposits; hydrocarbons; hydrocarbon geochemistry; hydrocarbon potential;
hydrocarbon generation; Athabasca Basin; Douglas Formation; Precambrian; Proterozoic |
| Illustrations | location maps; cross-sections; plots |
| Program | Targeted
Geoscience Initiative (TGI-4), Uranium Ore Systems |
| Abstract | The Proterozoic Athabasca Basin in Canada is known for its world-class, high-grade uranium deposits developed near the unconformity between the basin and the basement. The Douglas Formation in the upper
part of the preserved strata in the basin contains total organic carbon (TOC) of up to 3.56 wt.%. Previous studies of organic matter maturation and hydrocarbon inclusions indicate that oil and gas have been generated from this formation, and that
some hydrocarbons found in the unconformity-related uranium deposits were derived from the Douglas Formation. This study aims to evaluate how the oil and gas generation processes may have affected the fluid overpressure development in the basin, and
whether or not the hydrocarbons generated in the Douglas Formation could migrate downward to stratigraphically lower intervals and eventually to the sites of mineralization near the unconformities. We carried out a series of numerical experiments to
examine fluid overpressures, flow directions, temperatures, and oil and gas generation processes using a two-dimensional conceptual model derived from a geologic cross-section from the basin center to the eastern margin. An additional 5 km strata
were added to current basin stratigraphy to account for observed paleogeothermal data. Variation studies were undertaken to account for uncertainties in the lithologies of the eroded strata, and the wide ranges of possible permeabilities of different
lithologies and kinetic parameters of oil and gas generation. It is found that, if moderate permeabilities are used in the modeling for each lithology (known as the base model), oil and gas generation processes contribute little to the development of
fluid overpressure, and fluid pressure in the basin is close to hydrostatic regardless of whether or not hydrocarbon generation in the Douglas Formation is included in the modeling. However, if permeabilities are assigned values one order of
magnitude lower than in the base model, significant fluid overpressures are developed in the eroded strata in the upper part of the model. In the base model, oil generated in the Douglas Formation may migrate downward, driven by an overpressure zone
situated above the Douglas Formation, but gas migrates upward. In the low-permeability model, however, the overpressures developed above the Douglas Formation are so high that both oil and gas generated in the Douglas Formation migrate downward. The
numerical modeling results thus indicate that it is hydrodynamically possible for oil and gas generated in the Douglas Formation to migrate to the base of the basin and reach the sites of the unconformity-related uranium deposits. |
| Summary | (Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience
knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The Proterozoic Athabasca basin in Canada is known for its world-class, high-grade uranium deposits developed near the
unconformity between the basin and the basement. Previous studies have proposed that oil and gas were generated from upper strata in the basin and that some of these hydrocarbons played a role in formation of the unconformity-related uranium
deposits. The numerical modeling generated in this study indicate that it is hydrodynamically possible for oil and gas generated in the upper strata to migrate to the base of the basin and reach the sites of the unconformity-related uranium
deposits. |
| GEOSCAN ID | 293331 |
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