The Evolution of Water Saturations in the McMurray Oil Sands: A Product of Geological History and Capillary Pressure
Notice bibliographique
Résumé
Abstract This paper examines the role played by geological history and by capillary pressure in the evolution of the unusual water saturations of the McMurray reservoir of the Athabasca Oil Sands Region (AOSR). The McMurray formation water and bitumen have been a dynamic system evolving through geological time in order to maintain equilibrium between buoyancy and capillary pressure. The main driving force was the change in hydrocarbon as well as formation water density so that they became similar in value. These changes were likely caused by a combination of factors including hydrocarbon biodegradation, reduction in temperature and pressure through erosion of the overburden above the McMurray, and lowering of water salinity. The weakening of buoyant forces would enable capillary pressure to increase the average water saturation and to redistribute water and hydrocarbon so that water was preferentially moved to areas with a higher fines fraction. The paper reviews pertinent geological history and discusses theoretically how water saturation should have changed as a result of changes in oil/bitumen and in formation water density. Field data from two sites with different levels of biodegradation as well as a conventional non-biodegraded analogue were analyzed in light of the theoretical expectations. There will be water saturations above irreducible levels and hence some water mobility throughout much of the McMurray. There also is evidence that the irreducible water saturation in good quality McMurray reservoir sands at one site is ~ 10% or less. It is possible that the present McMurray irreducible water saturation levels are somewhat similar to what they were at the time of first oil charge approximately 80 million to 110 million years ago. High-water saturation zones form when biogenic gas in depleted gas caps is replaced by water, as concluded by Fustic at al., (2013). As water is drawn into the depleted gas cap from the surrounding reservoir, water saturation can be lowered to nearly irreducible levels at the base of the reservoir below. Capillary pressure can also create transition zones below these high-water saturation zones. Therefore, thin depleted paleo-gas caps could create zones of elevated water saturation much thicker than the original gas caps. There can be significant heterogeneity in these high-water saturation zones across the McMurray Formation and at field scale.
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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 | 0,000 |
| 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.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».