Bibliographic record
Abstract
Abstract Matrix permeability of shales is an elusive but important parameter in characterizing shale gas reservoirs. Permeability is typically measured using steady-state flow tests or the more timely transient methods such as pulse-decay. Due to the low permeability nature of shale rocks, slip flow regime is observed to be dominant in pore scale. As a result, permeability changes with pore pressure. Traditionally, permeability is measured at various mean pore pressures and the data is used to extract the Klinkenberg or absolute permeability. However, it has been shown recently that Klinkenberg permeability significantly overestimates the absolute (liquid) permeability of shale rocks. Additionally, several studies have shown different methods of permeability measurement can lead to significantly different results at similar pressures. In this work, steady-state laboratory gas flow experiments have been conducted on four shale samples using methane and nitrogen as flowing fluid. At each stage, mean pressure and mean effective stress is held constant and permeability is measured at various gas flow rates. Mean pressure is then raised and the tests are repeated at the next stage. The tests are designed to study the influence of mean pressure as well as flow rate on gas permeability. Subsequently, the samples are sheared in a triaxial cell and similar permeability tests are repeated to compare the permeability behavior before and after shearing. Finally, the samples are saturated with water to measure water permeability in order to analyze the gas permeability observations using theory. The results indicate strong rate sensitivity in shale permeability measurements. Measured shale permeability is observed to rise as flow rate increases and reaches a constant value at higher rates. Permeability of sheared samples shows a similar trend although with higher permeability values. This phenomenon casts a shadow of doubt around the common non-steady-state permeability measurement methods and has never been discussed previously with respect to shale gas reservoirs. The basic definition of gas permeability needs to be revisited in order to set up new standards (concerning testing pressure, rate, and stress state) in order to obtain meaningful and comparable permeability measurements.
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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) | 0.001 | 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".