Aquifer Controls on Coalbed Methane Development in the Powder River Basin, Wyoming
Bibliographic record
Abstract
Abstract Development of coalbed methane (CBM) in the Wyodak-Anderson seams of the Powder River Basin, Wyoming, is one of the most active plays in the world. Compared to other CBM producing basins, the Powder River Basin subbituminous coal has relatively low gas content (20–50 scf/ton), but high permeability (100s of millidarcy to 1+ darcy). Because of the shallow depth, Powder River Basin CBM development is normally on 40- or 80-acre well spacing. Another significant difference between the Powder River Basin and other producing CBM basins is the fact that the coal seams of the Powder River Basin are overlain and underlain by large, thick aquifers that are essentially infinite-acting in nature. The degree of hydraulic connection between these aquifers and the coal is a critical factor in the economics of gas production from this play. Where the aquifers are well connected to the coal, water influx or leakance is high, leading to a nearly steady-state pressure environment that will deter efforts to dewater the coal and produce methane. Using reservoir simulation analyses and actual field data on gas and water production, this paper examines the effect of aquifer leakance on the producibility of the coal. Optimum well spacing in the Powder River Basin is shown to depend on having sufficient wells per section to lift the water that leaks into the coal from the aquifers. In fact, in some parts of the basin, aquifer leakance will maintain reservoir pressure high enough that it will curtail methane desorption and restrict ultimate gas recovery. Further testing and analysis to better characterize the aquifers and their connection to the coal is necessary.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".