Gas Hydrates Offshore Eastern Canada: Fuel For The Future?
Notice bibliographique
Résumé
Abstract Continental margins of Canada represent vast potential for storing hydrocarbon gas (largely methane) in the form of gas hydrate. The theoretical stability field for gas hydrate encompasses some 120,000 km2 along the Scotian margin. Examination of >34,000 line-km of industry 2D seismic reflection data along this margin; however, resulted in identification of only one area with a clear bottom simulating reflector (BSR). This BSR forms over 280 km2 at 350–450 mbsf and lies within the stability field for methane gas hydrate. Seismic velocity models derived from wide angle reflection and refraction analysis over this BSR include velocity inversions of 50–75 m/s between a 60–120 m thick high velocity zone (HVZ) and a 150–260 m thick low velocity zone (LVZ) at sub-bottom depths of 325–425 mbsf. Similarly these results indicate that hydrate concentrations at the study site range from 2–6% and free gas < 1%. Hydrate above the BSR is estimated to be 0.44–1.33 × 109 m3 in volume, as a result. Hydrates may exist elsewhere along the margin but lack of BSRs make them difficult to detect. Introduction Gas hydrates are believed to represent a large storehouse of methane gas in sedimentary basins around the world1 and especially in Canada because of extensive northern permafrost and offshore land areas.2,3,4 In Canada, hydrates have been known to exist for some time along the Cascadia margin, offshore Vancouver Island, initially with the recognition of bottom simulating reflections (BSR),5,6,7,8 followed by Ocean Drilling Program (ODP) sampling.9,10 They have also been recognized and sampled in the onshore MacKenzie delta region.11 Gas hydrates or clathrates have been recovered through drilling, coring and even fish trawling in the case of Cascadia.12,13 Estimates of the volume of hydrates in Canada indicate that there may be as much as 1012-1014 m3 of methane gas bound in hydrate.3 Despite occurrences on the west coast and northern regions of Canada, no physical and little geophysical evidence for hydrates had been published from Canada's east coast margin, although their presence has been surmised and the calculated stability zone is significant in size.3,4,14,15,16,17 It is the intent in this paper to document the first unequivocal observations of BSR's on the Nova Scotia margin of Canada (Fig. 1), indicating the possible presence of gas hydrates. Seismic reflection, wide-angle reflection and refraction data are used to characterize the zones around the BSR. The possible existence of hydrate in this continental margin setting is significant for a number of reasons:hydrates may represent a potential hazard to hydrocarbon exploration and development,hydrates may be an indicator of an active petroleum generation system with fluid migration, anddocumentation of global occurrences of methane hydrate has important implications for carbon cycle and climate change investigations. In future, hydrates may also represent a significant hydrocarbon resource. Geologic Setting
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Comment cette classification a été obtenuedéplier
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 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».