The impact of rock composition on geomechanical properties of a shale formation: Middle and Upper Devonian Horn River Group shale, Northeast British Columbia, Canada
Bibliographic record
Abstract
ABSTRACT The geomechanical properties of a shale reservoir are essential both to the development of natural fractures and to the formation’s response to hydraulic fracture stimulation. We evaluate the rock mechanical properties of the Middle and Upper Devonian Horn River Group shale, including the Evie and Otter Park Members and the Muskwa Formation, applying core hardness measurements and log-derived Young’s modulus, Poisson’s ratio, and brittleness and relating these to shale composition and texture. Clay content is the most significant factor controlling the brittleness of shale rocks. The effect of quartz content on rock mechanical properties depends on the type of quartz present in the rock: authigenic quartz is positively correlated with brittleness, but detrital quartz has little or no effect. Factor analysis indicates that carbonate increases brittleness, although no obvious correlation between total organic carbon content and brittleness was observed. Depositional facies are related to geomechanical properties, because each facies has a distinctive composition. Massive mudstone and pyritic mudstone are relatively brittle because of abundant authigenic quartz cement. Laminated mudstone and bioturbated mudstone are relatively ductile, because most detrital carbonate and quartz grains are set in a matrix of clay minerals. Brittleness in the Horn River Group shale shows both geographic and stratigraphic variability. Increasing brittleness in the northwestern part of the basin largely results from greater distance from the clastic sediment source. The Otter Park Member represents a period of major relative sea-level fall and is relatively ductile because of its high clay content, whereas the underlying Evie Member and the overlying Muskwa Formation are relatively brittle because of high carbonate and biogenic silica content, respectively.
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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 | 0.001 |
| 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 | 0.001 | 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".