An Alternative Technique for Fast Permeability Measurements of Gas Shales
Bibliographic record
Abstract
Abstract Laboratory pulse-decay techniques are effective for determining rock permeabilities ranging from 0.01 μd to 0.1 md. However, the measurement time is fairly long, reaching up to several hours to days when testing gas shales because their permeability can be as low as dozens of nano-Darcys. This paper proposes an alternative pulse-decay technique that offers accurate permeability measurements within a considerably short time frame. A radial-flow pulse decay method with a new experimental design is developed, which employs two gas reservoirs of the same volume and two pressure pulses with the same magnitude, one "positive" and one "negative". A mathematical model is then developed to numerically verify the feasibility of the newly developed technique and analytically solved for permeability estimation. Pressure responses with time in the radial direction of the test sample are analyzed and compared with those in the axial direction by solving the mathematical model. A concentric circular cavity with a diameter of 0.51 cm is created along the core samples, which are tested to experimentally demonstrate the applicability of the technique. The numerical results showed that the pressure pulse of the radial flow decays much faster than the axial flow and at least a 10-fold reduction in measurement time can be achieved. Numerical results indicated that the proposed technique is capable of eliminating the effects of the compressive storage and gas sorption in the permeability measurement; while great efforts need to be put to correct such effects when employing conventional transient techniques. An in-depth comparison is experimentally made between the proposed method and the conventional axial-flow method. The experimental results presented in the study confirm that fast and accurate measurements can be achieved using the proposed technique.
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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 | 0.001 | 0.001 |
| 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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".