Western Canada Sedimentary Basin petroleum systems: A working and evolving paradigm
Bibliographic record
Abstract
Western Canada Sedimentary Basin (WCSB) crude oil source rocks accumulated typically in “starved” depositional settings of Sloss outer detrital facies belts and lesser stratigraphic cycles. These produced petroleum from marine type II organic matter in response to burial by commonly westward-thickening overlying successions. Oil occurs commonly within the “Sloss” sequence containing its source rock, often up dip from the “petroleum kitchen.” Migration pathways cross stratal contacts, unconformities and structures, and much oil migrated into adjacent sequences, especially into Lower Cretaceous Mannville Group reservoirs. Anaerobic biodegradation affects oil quality and generates secondary biogenic gas. The WCSB oil system paradigm predates the recognition of anaerobic biodegradation. Biodegradation in post-Mannville reservoirs remains underappreciated. Natural gases originate by thermogenic and biogenic mechanisms from kerogens, coals, and crude oils. Gases are variably altered: physically, microbially, and inorganically. Few oil studies addressed solution and associated primary thermogenic or secondary biogenic gas. Gas studies are independent of oil studies and none recognize secondary biogenic gas even in association with biodegraded oils. We hypothesize that secondary biogenic gas occurs commonly, often mixed with other gas, to produce hydrocarbon isotope ratios and variations distinctive from primary biogenic and thermogenic gases. Where Mannville oil pools have sources in underlying marine rocks, Mannville gases are attributed largely to nonmarine sources. Currently, cross-stratal migration is inferred less commonly for gas than for oil. The inference of gas stratigraphic immobility is problematic for biodegradation studies that infer large secondary biogenic gas fluxes into soil and atmospheric sinks, the migration pathways of which pass through Cretaceous strata. In some unconventional plays, gas isotopic “rollover” and “reversal” due to thermal cracking has implications for reservoir performance. Efforts to understand Cordilleran petroleum systems merit investigation to extend unconventional resource plays westward from Interior Platform.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.008 | 0.010 |
| Science and technology studies | 0.010 | 0.020 |
| Scholarly communication | 0.013 | 0.006 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 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".