Shear Dilatancy in Unconsolidated Laboratory Samples Improves Relative Permeability Performance
Bibliographic record
Abstract
Abstract Steam Assisted Gravity Drainage (SAGD) can cause dilatant shear failure in unconsolidated heavy oil reservoirs. Our experimental work documents changes induced by such shear failure in absolute permeability, relative permeability to oil and water, and residual saturations. Tests were performed on 2 inch diameter synthetic specimens made from lower fine to medium grain size Ottawa sand formed with wet vibration to an initial porosity of about 32%. Loading paths included triaxial compression and radial extension. Axial and volumetric strains were measured directly during deformation, and single and two phase permeability tests were executed at axial strains of 1 to 10%. Triaxial compression tests followed a path of increasing mean stress (under constant confining stress) while radial extension tests provided a decreasing mean stress loading path (reducing confining stress under constant axial stress). The relative permeability was determined by the unsteady state method for relative permeability endpoint assessment. Results show similar absolute permeability trends to those published by others, but our multiphase measurements appear unique. Relative permeabilities are more strongly influenced by shearing, with water relative permeabilities being increase by as much as a factor of 2. The effect seems to be slightly greater for finer grain sand than for the medium grain size. Absolute permeability changes were greatest for the samples with the lowest initial porosity, which would include those that were poorer sorted. Poorer sorting of the sand pack seems to reduce the impact on relative permeability changes, however. Residual oil saturations were reduced from 0.28 to 0.13 in the lower fine Ottawa sample, suggesting the possibility for significant improvement in oil recovery when the sand is sheared. During triaxial testing, it was interesting to note that at 50 psi effective confining stress, absolute permeability increased with shearing, but at 200 psi effective confining stress, absolute permeability was reduced, even though the volumetric strain was still dilatant. In addition to providing new data on the magnitude of absolute permeability and multiphase flow properties for unconsolidated sands, this paper also demonstrates that dilatant shear failure does not guarantee increased flow capacity for such rocks.
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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) | 0.002 | 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".