Deformation Band Control on Hydrocarbon Migration
Bibliographic record
Abstract
Abstract The hydrocarbon potential of sandstone reservoirs may be significantly affected by postdepositional compartmentation by grain-scale deformation mechanisms such as pressure solution, dislocation creep, microfracturing, and small-scale faulting. Deformation bands, sub 1-mm-thick elongate layers characterized by intense localized brittle fracturing, are important small-scale structural features controlling fluid flow in reservoir sands. They can act as fluid pathways or as barriers to fluid flow, depending on the timing relationship between hydrocarbon charge and deformation. Characterization of deformation-band scale, distribution, and timing of deformation relative to hydrocarbon charge is therefore critical in a full assessment of reservoir history. Integrated CL and UV studies of fluid inclusions from the Jeanne d'Arc Basin, Newfoundland, demonstrate that hydrocarbon charge predated deformation-band formation because oil-trapping quartz overgrowths are clearly cut by deformation bands. In contrast, porous, bitumen-rich sandstones from the Upper Old Red Sandstone of Caithness, NE Scotland, contain hydrocarbon inclusions trapped in quartz overgrowths that formed after deformation. Detailed petrographic work and CL imaging of these Old Red Sandstone samples demonstrates that hydrocarbons are absent in cemented deformation bands and occur only in undeformed sandstone pores and late quartz overgrowths. Post-deformation hydrocarbon migration pathways were thus constrained by effectively sealed deformation bands. In a third example, from the Jurassic of Skye, there is evidence for hydrocarbons in early (pre-band) cements, entrainment of hydrocarbons during band development, and a later pore-filling oil charge, indicating a complex relationship between the migration history and the bands.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".