Sequence stratigraphic analysis of the Duvernay Formation, Kaybob area, Alberta, Canada
Notice bibliographique
Résumé
The Upper Devonian Duvernay Formation is an important hydrocarbon source rock in the Western Canada Sedimentary Basin and has been a significant unconventional oil, gas liquids, and gas reservoir since 2011. Heterogeneity in this and other shale reservoirs is important in predicting rock properties (such as TOC, porosity, permeability, and brittleness) within self-sourced reservoirs to identify target intervals. These properties can change with systems tracts and position within a basin at several scales and can be predicted by sequence stratigraphic models. In this study, we characterize the lithofacies of the Duvernay Formation and develop a sequence stratigraphic model for the formation in the Kaybob Area of Alberta. We also identify a set of features characteristic of mudstone sequence boundaries, describe how they vary stratigraphically and geographically, and interpret processes responsible for their formation. Five lithofacies were identified in 11 Duvernay cores from the Kaybob area of Alberta, characterized by composition, grain size, sedimentary structures, bioturbation, and cement. Lithofacies were deposited by a combination of suspension settling, sediment-gravity flows, and bottom currents under anoxic to fully oxygenated bottom water conditions. Lithofacies distribution was strongly affected by proximity to sediment sources, bottom topography, and sea level cyclicity. Relatively coarse-grained, carbonate-rich, bioturbated, and organic-poor facies are common close to large carbonate platforms and reefs; silt- and sand-rich facies deposited by bottom currents and sediment gravity flows are common on the slopes of large carbonate platforms; hemipelagic deposited, fine grained, biosiliceous, organic-rich facies are common in distal areas of the basin. Transgressive deposits are characterized by increasingly fine-grained, biosiliceous, organic-rich facies; highstand deposits by increasingly coarsegrained, carbonate-rich, bioturbated, organic-poor facies; lowstand deposits by detrital clay-rich, bioturbated facies. Sequence stratigraphic surfaces were identified in the 11 cores and correlated across a network of approximately 600 wireline wells in the Kaybob area to develop a sequence stratigraphic model. Three 3rd order depositional sequences and 4th order depositional sequences are identified within the Duvernay. Two types of 3rd order sequence boundaries are identified, their expression dependent on their position within a 2nd order depositional sequence that encompassed the Duvernay. In the 2nd order transgression, sequence boundaries are expressed as scoured surfaces with coarse overlying lags that represent a period of sediment starvation and reworking during lowstand conditions and early transgression. In the 2nd order highstand, sequence boundaries are expressed as soft sedimentdeformed surfaces overlain by coarse beds that represent a period of forced regression, with the sequence boundary located at the top. Surfaces become gradational and overlying lags or forced regressive deposits thin basinward. The high-density data set in our relatively small study area enables us to map 3rd and 4th order sequence stratigraphic surfaces across the study area with a high degree of certainty. We were also able to interpret major sources of sediment and determine geographic extent of topographical features during different stages of Duvernay Formation deposition from geographic distribution of facies and variations in systems tract isopachs. Our interpretation of sequence boundaries produced during a 2nd order TST are consistent with several previous studies that interpreted sequence boundaries in mudstones as combined sequence boundaries and transgressive surfaces overlain by winnowed lags. Our interpretation of sequence boundaries produced during a 2nd order HST differs from previous studies in that we propose the coarse sand beds at sequence boundaries were deposited during forced regression, with the sequence boundary located at its top.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,010 | 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 ».