Arctic Drilling Hazard Identification Relating to Salt Tectonics
Notice bibliographique
Résumé
Abstract The focus of this study is to improve our technical understanding of anticipated drilling hazards in the Arctic Circle, especially hazards relating to drilling into and adjacent to evaporitic (salt) structures and associated tectonics. We explore current drilling technologies available to us to mitigate any anticipated drilling hazard. We demonstrate applicable operational experiences from other areas similar to drilling in the Arctic. The Arctic's vast oil and gas potential has spurred exploration since mid-20th century. Government institutions such as the Geological Survey of Canada and historic companies such as Panarctic provide critical information on geology and petroleum discoveries. U.S. Geological Survey (2008) published Arctic mean estimated undiscovered technically recoverable conventional oil and gas resources at a total of 412 billion barrels of oil equivalent (BBOE). Exploration in the Arctic varies in complexity mainly based on the depth drilled and hazards encountered. The remoteness of drilling anywhere in the Arctic makes both onshore and offshore operations generally more complex than drilling elsewhere in the world. To put it in perspective, our research into drilling time in deepwater Nova Scotia show for the majority of high complexity wells, non-productive time (NPT) can exceed 24% of total drilling time, and half of documented NPT is contributed to formation related problems. Our geological analysis has found that Arctic petroleum basins and margins such as the Sverdrup Basin and East Canada and show comparable salt tectonics to Nova Scotian continental margin, offshore Brazil and Angola. Salt diapirs, salt domes, and thicken salt sections are common occurrences. Associate structures such as anticlines, extensional growth faults, wrench faults are observed in these basins. Extensional growth faults, listric normal faults, thrust faults, flank-salt shears, and brecciated fault zones are associated with salt bodies. These structures are planes of weakness. Depending on effective in-situ stress conditions these faults and intense natural fractures can become critically stressed and induce slip on plane. Salt rheology and geochemistry pose higher drilling risk than drilling through other rocks. Salt creeps towards borehole during drilling, and plastic yielding around borehole is unavoidable when drilling through salt body. Boundary zone tends to be heavily naturally fractured, brecciated, or sheared, and rock may become unconsolidated and lose its cohesiveness. Taking heavy losses in naturally fractured boundary zone may occur. Abnormal pressure exists and taking a kick while drilling out of salt body is not uncommon. Public domain documentation available for Arctic region support the hazards identified by our geological analysis and also suggest that a great deal of downhole uncertainty exists during early exploration. In analogous setting outside of the Arctic Circle, drilling problems related to pressure uncertainty, tight windows and wellbore stability are referenced throughout and the lessons learned suggest limiting the uncertainty when possible and the use of contingency planning. Based on the similarities in the structural geometry of petroleum basin in Arctic and select basins in other parts of the world, it seems logical that lessons learned from these areas away from the Arctic, e.g., offshore Nova Scotia, Brazil, and Angola should provide some assistance with the planning and execution of Arctic drilling activities. All information collection during this study has been referenced throughout. This information will be beneficial for continued support of drilling in salt tectonic structural provinces in the Arctic and anywhere else in the world.
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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 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| 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 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 ».