Methane Transport through Nanoporous Shale with Sub-Irreducible Water Saturation
Bibliographic record
Abstract
Abstract Characteristics of gas transport in nanopores are topics of great interest for evaluation of unconventional reservoirs. The apparent permeability model for single-phase gas flow has been extensively investigated. Few models, however, have been established for the gas transport in gas/liquid two-phase flow condition. Unfortunately, initial water always exists under reservoir condition. Although it is regarded as immobile state, the impact of which on gas flow capacity should not be simply neglected. In this work, firstly, the state of sub-irreducible water saturation in unconventional reservoirs have been carefully investigated, and the thickness of thin film bound on inorganic pore surface (e.g. clay or quartz) has been quantified. Subsequently, by considering the impact of the water film on the effective hydraulic diameter, gas slip-flow model is established. Noting that the gas phase in moist conditions is mainly composed of both methane and vapor rather than single-component methane. Thus, the methane-vapor binary gas state equation has been introduced to describe the real gas effect under high pressure and temperature condition. Our proposed model has been directly verified by the laboratory tests, and the gas relative permeability in different cases with varying Knudsen numbers has been computed. To our surprise, the calculated relative permeability curves for gas transport in narrow pores demonstrate as convex shape, which indicates that the influence of water on gas flow weakens as the increase of irreducible water saturation. This phenomenon become obvious especially in large Knudsen number condition. In fact, as the increase of Knudsen number, the gas slippage becomes significant and the relative impact of pre-adsorbed water reduces. For a typical tight gas reservoir with initial water saturation of 30%, the effective permeability for gas transport will reduce about 15%~30%, which depends on the Knudsen number for gas transport. Therefore, neglecting the effect of two-phase interaction might overestimate the gas deliverability.
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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".