Experimental Study of Stress Dependent P-and S-wave Velocities in Both Dry and Saturated Sand
Notice bibliographique
Résumé
Vp/Vs ratio is known as lithological and fluid prediction method as well as key part of AVO analysis. This diploma thesis is based on the based on the theoretical and mainly experimental studies to evaluate the behavior of velocities with stress and strain with different stress path. As the physical and chemical behavior of the sediments change with change in overburden stress which has not only influence on the sediments grain structures, sizes, angularity and sorting but it has also a strong influence on elastic and acoustic properties of the rocks. The main idea of the present study was to find that at what extent pore fluid has an effect on the acoustic properties of the sand and sandstone. So for this different experiments has been performed in the laboratory in an oedometer setup with different percentage of brine and also with different grainsized samples both for dry and saturated cases to see the clear effect of fluid on velocities and also the velocities behavior with stress. Data included both the P- and S- wave velocities, strain sensitivity with stress and also porosity change with stress. In the present study the for case#01 in which Ottawa (OT) sand with different percentage of brine were tested in uniaxial conditions performed in an oedometer setup. The vertical P- and S- wave velocities are found much higher with high concentration of the brine which could possibly because of the sample stiffness which increases with an increase in brine percentage. Moreover the changes in velocities are also found because of an increase in net vertical stress which needs to be considered as well. Similarly the Vp/Vs ratio decreased with in an increase in external stress but at lower stress level it seems to be relatively stable. For the first case stress sensitivity with strain, as all the samples were compacted about 11.0 MPa net vertical stress, so it can be termed as consolidation samples, therefore less strain sensitivity would expected. But the samples with high concentration of brine show high strain sensitivity and viceversa. All the samples show the strain hysteresis because of their inelastic behavior as none of the samples returns to its original shape. Porosity reduction with stress was not found higher so it was more or less stable. For the second case#02 in which different samples were used with different grain sizes but with same percentage of brine to see the possible fluid effect on velocities and also grain size. But it was clearly observed that P- wave velocity after fluid substitution went higher as compared to the velocities in dry samples. However there is no such change has been found in case of S- wave as it doesn t have any effect with the fluid. In this case velocities were found also stress sensitive as in first case. Similarly there was not such difference has been observed in velocities due to change in grain sizes. While the behavior of, stress strain sensitivity and porosity reduction with stress was found more or less same as in case#01 as discussed above.
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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) | 0,001 | 0,001 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 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 | 0,001 |
| 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 ».