The Upper Devonian-Lower Mississippian Bakken Formation of west-central Saskatchewan: stratigraphic architecture and sequence stratigraphy of a conventional heavy oil reservoir
Bibliographic record
Abstract
Abstract The Bakken Formation (Upper Devonian-Lower Mississippian) of western Saskatchewan has lower and upper members dominated by black shales and a heterolithic middle member, similar to southeastern Saskatchewan and North Dakota. However, the middle member in western Saskatchewan contains fine-grained sandstone where porosity and permeability values commonly exceed 25% and 1 Darcy respectively that are absent in southeastern Saskatchewan and North Dakota. Although focus has been in southeastern Saskatchewan and North Dakota, the Bakken Formation of west-central Saskatchewan has conventionally produced heavy gravity oil (API approximately 12 degrees) since the 1950s using vertical wells. The sequence-stratigraphic framework of the Bakken Formation of west-central Saskatchewan includes deposition under open-marine and marginal-marine conditions. Open-marine black shales were deposited during late-stage transgression (TST1) and progradation of offshore siltstones during the subsequent highstand systems tract (HST). Fine-grained sandstone, siltstone, and mudstone showing evidence of tidal influence was deposited during a falling-stage systems tract (FSST), initiated under forced-regressive conditions. Increased fluvial influence and dilution of normal marine salinity established marginal-marine conditions, evidenced by the low bioturbation index (BI: 0−2). Subsequent transgression (TST2) led to increased marine influence, reflected in a sudden increase in biogenic activity (BI: 4−5). Offshore siltstone and black shale were deposited through continued transgression (TST2) resulting in the re-establishment of open-marine conditions. Preserved thickness of the Bakken Formation in west-central Saskatchewan has been affected by post-Mississippian erosion during the creation of the sub-Cantuar drainage network, which was later filled by Lower Cretaceous clastics. The Bakken middle marginal-marine interval in west-central Saskatchewan differs from that in southeastern Saskatchewan. Fine-grained sandstones associated with tidal channels in west-central Saskatchewan comprise a reservoir characterized by porosity and permeability values that commonly exceed 25% and 1 Darcy, respectively. In contrast, in southeastern Saskatchewan, the Bakken Formation produces from a dolomitized silty sandstone where low porosity and permeability values have led to the widespread use of unconventional exploitation techniques to produce economically.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".