Geomechanical Properties of Clearwater Shale at Elevated Temperatures
Notice bibliographique
Résumé
Abstract Caprock integrity is essential to the success of Steam Assisted Gravity Drainage (SAGD) operations. This issue is especially critical in the case of shallow SAGD operations where the in situ stresses are relatively low and, by necessity, the steam pressure has to be limited in order to ensure the safety of the process. Limited information is available on changes in caprock material properties that occur when temperature and stress conditions change in areas of the caprock affected by SAGD. By including these changes in caprock properties in the calculation of maximum operating pressure (MOP), it is possible that the allowable MOP could increase. This would allow the sealing capability of the caprock to be exploited more fully and provide an avenue for improving the economics of shallow SAGD operations. This paper presents the results of experiments measuring geomechanical properties of Clearwater caprock, at both ambient temperature (25°C) and elevated temperature (115°C and 200°C). The shale samples used in the tests were cut from two sets of shale cores that had been obtained from the Wabiskaw Member of the Clearwater Formation at Athabasca oil sands SAGD projects. The first set of core samples originated from a depth of approximately 200 m. The second set was obtained from a different site and a shallower depth, approximately 150 m. The purpose of these experiments was to study the effect of temperature on geotechnical properties such as the elastic parameters (bulk compressibility, Young’s modulus, Poisson’s ratio) and shear strength parameters (cohesive strength, friction angle), and to investigate the behaviour of shale permeability in a stress, pressure and temperature environment similar to one that might exist during SAGD operations. The experiments were performed in a triaxial cell, under conditions in which the pore pressure and axial and confining (radial) stress were controlled. The triaxial compression tests indicated that the elastic properties and shear strength of the shale samples were sensitive to temperature, for the range of effective stresses used in the tests. While the change in bulk compressibility was negligible, the samples became much stiffer (higher Young’s modulus) and stronger (higher cohesion, lower friction angle) at elevated temperature. The measured increases in permeability caused by a reduction in effective stress were relatively small, usually not greater than a factor of ten over the initial permeability. In one exceptional case, at elevated temperature, the permeability increased by a factor of nearly one million, but even in this case the maximum permeability measured was never larger than 10 md. A substantial portion of the change in permeability occurred after the sample failed in shear. The increase in permeability that was measured on the Clearwater shale samples at elevated temperature was somewhat greater than at ambient temperature, particularly at larger volumetric strains. At present, only a limited number of tests have been carried out to measure changes in caprock properties under temperature, pressure and stress conditions that prevail during SAGD. Further tests would be required to establish a better quantitative understanding of these changes in caprock properties.
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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 | 0,000 | 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) | 0,001 | 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 ».