Laboratory Investigation on the Permeability of Coal During Primary and Enhanced Coalbed Methane Production
Notice bibliographique
Résumé
Abstract Coalbed Methane (CBM) has grown into an important natural gas resource in North America in recent decades. The economical development of CBM heavily relies on coal permeability. The coal permeability is provided through a network of coal cleats and natural fractures. It is greatly affected by the confining stresses and the coal matrix response during gas adsorption and desorption in primary and enhanced recovery processes. This paper is focused on a laboratory investigation of coal permeability variability with different operating parameters. Core flood experiments in coal have been conducted with methane production and methane displacement by CO2. The permeability to different gases (CH4, CO2) under equilibrium conditions was measured at different confining stresses. The coal permeability to helium, which was reported in previous work, provides a comparison baseline. The permeability of a coal core to gases shows a strong dependence on net confining pressure, and exhibits strong hysteresis. The CH4 permeability is relatively smaller than the corresponding He permeability demonstrating a swelling effect of coal by CH4. The adverse effect of CO2 on coal permeability is also shown. The paper focuses on the experimental results obtained to date. Introduction Coalbed methane (CBM) is an unconventional natural gas resource that gains increasing worldwide attention. Using CO2 for enhanced CBM production or using coal beds for CO2 sequestration has also received intense research interest in recent years. CO2 has been proven to have more than twice the affinity to coal than CH4(1). Limited studies have shown the concept of CO2-ECBM to be technically viable. However the mechanisms have not been studied in detail. Permeability of coal is recognized as the most important parameter controlling CBM and ECBM (enhanced CBM) production. Coal cleats are responsible for the permeability of coal. Flow through the cleats is dominated by Darcy flow that relates flow rate to permeability and pressure gradient(2). Methane is the major component of the coalbed gas. Measuring coal permeability to methane is crucial for evaluating CBM production rate. When injecting CO2 into the coalbeds in the ECBM production, the interaction of coal with dense CO2 can be inferred from the permeability changes. Measuring coal permeability to CO2 is the fundamental step to investigate the CO2-ECBM process and potential of CO2 sequestration. Measuring meaningful coal permeability is more difficult than measuring reservoir rock permeability. Only a limited number of research groups have measured the permeability of coal by core flooding, and have pointed out some of the associated difficulties(3), (4), (5). Permeability is provided to coal by the cleats and depends on cleat orientation, spacing, and aperture. The coal matrix swells and shrinks during adsorption and desorption of gases(6), (7). As reservoir pressure is depleted, the net stress due to overburden increases, leading to closure of the cleats. At the same time, gas desorption causes coal matrix shrinkage, which leads to cleat opening. Different gases adsorb on coal to different degrees and are expected to cause different degrees of swelling or shrinkage.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
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