The Influence of Discontinuities on Geomechanical Analysis of the Joslyn SAGD Steam Release Incident
Notice bibliographique
Résumé
Abstract A noteworthy caprock failure occurred on the Joslyn Steam Assisted Gravity Drainage (SAGD) project in 2006 that continues to have a significant impact on the approval process for future SAGD projects. Two major reports were released by Total E&P Canada Ltd. as operator and Alberta Energy Regulatory (AER), respectively. A number of potential mechanisms were postulated within those studies, but without a definitive resolution. Inclusion of a fractured medium in the assessment of caprock integrity has not been extensively studied for detection of failure modes. The objective of this paper is to explore the effects of existence of discontinuities (e.g. fractures or fissures) in caprock, loading conditions, and steam chamber evolution, on surface heave, joint normal and shear displacements. Different modes of failure under various scenarios are presented for fissured and non-fissured caprocks. In this paper, a distinct element code was utilized to simulate the possible mechanisms of caprock failure during SAGD operation with various fracture sets in the Clearwater Formation caprock. Three-dimensional numerical models, including caprock and overburden, were simulated under different load conditions to evaluate the impact of steam injection pressure. The lower bound for maximum operating pressure (MOP) was based on the current AER formula and the upper bound was the injection pressure prior to caprock failure. Multiple realizations of fracture network in caprock were executed to reflect various geomechanical and geometrical properties of fractures. The results were compared with a previous study performed with the assumption of a continuum medium for a non-fissured caprock. For upper bound MOP conditions, the computed maximum vertical displacements at the base of caprock for models assuming 1) no fractures, 2) low fracture intensity, and 3) high fracture intensity were 79, 74 and 68 cm, respectively. It was observed that an increase in fracture intensity results in a reduction in vertical displacement at the base of caprock as well as surface heave. These variations in behavior are significant and illustrate that the assumption of a non-fractured caprock (in caprock integrity studies) may lead to conservative estimates of steam containment and ultimately, underestimation of the risk for caprock failure. At the base of caprock and under lower bound MOP conditions, a few local shear failure zones occurred above the pressurized zone, while for upper bound MOP conditions, larger zones of both shear and tensile failures were computed. It was also noted that the existence of fractures could cause local shear failure in the caprock, even below AER mandated values of MOP. Lastly, the findings of this study, including geomechanical simulations, uncertainties, and risk associated with evaluating caprock containment of SAGD operations were compared with previous studies. The results offer significant insight into our geomechanical understanding of the process in order to avoid a potential caprock failure during thermal projects, as unfortunately was experienced in the Joslyn SAGD steam release incident.
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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 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| 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) | 0,000 | 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 ».