Heavy oil accumulations in the Jeanne d'Arc Basin: a case study in the Hebron, Ben Nevis, and West Ben Nevis oil fields
Notice bibliographique
Résumé
The possibility of encountering heavy oil (gravity less than or equal to 25 degree API) has generally been perceived as a significant risk to hydrocarbon exploration in the Jeanne d'Arc Basin, a risk that is heightened by the lack of comprehensive published information on the subject. Hence, the processes responsible for heavy oil in the basin are evaluated in this report through integration of a broad range of studies, primarily focussing on the data-rich Hebron, Ben Nevis, and West Ben Nevis oil fields. Compilation of new and previously published geochemical data demonstrates that biodegradation is the principal cause of heavy oil discovered in the basin to date, although early generation of heavy oil from sulphur-rich source rocks is suspected in a small number of cases. The main factors controlling biodegradation through time are reservoir temperature, access to nutrients, salinity, hydrogen sulphide concentration, and the relative timing of key events such as hydrocarbon generation and charging of the reservoirs. Other causes of heavy oil are possible, but tend to be localized phenomena that are difficult to evaluate quantitatively given the current level of information. When evaluating the processes that may have led to biodegradation, events of the mid-Turonian ( about 90.5 Ma) prove to be very important. By this time, as confirmed by organic petrology and fluid inclusion studies, the major reservoirs of the Ben Nevis and earlier formations had been deposited and had received a significant charge of hydrocarbons. The spatial distribution of paleotemperature, investigated both through forward modelling of basin processes and through inverse modelling of apatite fission track data, was favourable for biodegradation in every reservoir that is known to contain biodegraded oil (i.e., temperature was greater than 60 degrees C). Also, seismic nterpretation reveals that significant erosion and possibly karstification occurred during the mid-Turonian. Indeed, with the exception of King's Cove A-26, the Petrel member is less than 20 m thick in every well that encountered biodegraded oil. In certain portions of the basin the Petrel Member and underlying Nautilus Shale, which are conventionally considered seals, may have been breached by circulating meteoric water that supplied nutrients to the oil-bearing reservoirs. Together, these observations form a template for evaluating the risk of biodegradation that can be applied quantitatively, after appropriate refinement of the models, to areas of the Jeanne d'Arc Basin that are outside the study area or to post-Petrel reservoirs. Several results are of broader interest. In particular, fluid inclusion and geochemical evidence suggest two distinct pulses of oil entered Ben Nevis Formation reservoirs. Possibly related to this, apatite fission track analysis indicates that rapid heating during the Early Cretaceous was followed by a period of significantly cooler temperatures between approximately the Aptian and Eocene and then by renewed heating that continues to the present-day. Further work is necessary to explore the significance of these results.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».