Enhanced Modelling of Sand Production Through Improved Deformation and Stress Analysis
Notice bibliographique
Résumé
Abstract This paper extends the capacity of the current sand production models by eliminating the influence of artificial conditions and numerical mesh on localization and deformation response in the sanding model. Past studies indicate strong size effects when using classical elastoplastic models. To rectify this deficiency, a fracture energy regularization method is implemented in the numerical model. The model incorporates both the geomechanical aspects (e.g. rock elastoplastic deformation and rock disaggregation) as well as the transport aspects (e.g. the role of seepage on rock deformation and solid release). The model employs a Mohr- Coulomb flow theory of elastoplasticity with friction hardening/cohesion softening. Emphasis is given on calibration procedure and validation of the enriched model through back analysis of triaxial and uniaxial compression tests. Next, the model is used to compare the numerical predictions with laboratory data on sand production. The comparison incorporates the stress and deformation as well as the sand volume. The calibration study shows that friction hardening and cohesion softening can satisfactorily reproduce numerically the weak sandstone response to various loading conditions. Further, computation results of strain softening material illustrate that fracture energy regularization strategy enables the model exhibit mesh invariance of the energy dissipation. Such invariance is of utmost importance in the sanding and wellbore stability studies where strain softening induces localization of plastic deformations in thin shear bands. Introduction In many physical situations (e.g., drilled wellbore), shear bands are observed. Shear bands form because of concentration of deformation in the medium in narrow bands in a process called localization. Development of a computational model that reproduces the observed damage evolution is necessary in the analysis of sanding and wellbore stability. Analytical and computational models formulated using a standard continuum description and a strength criterion are unable to recover the size effect (e.g. for wellbore stability the size effect is the effect of wellbore diameter on allowable field stresses), and are unable to produce results free of mesh design when the material undergoes degradation and strain softening. Localization can occur when a body composed of material softens (becomes weaker) with strain and the strain distribution within the body is slightly non-uniform. The element that carries the most strain then becomes weaker than the rest (i.e., it attempts to carry less stress). Since its neighbors carry the original stress, the boundaries of the weak element are thrown out of equilibrium (because the internal and external stresses do not balance). The weak element, therefore, starts straining more, which only causes it to soften more. This weak-link process is responsible for localization in a strain-softening material. Although localization is generally expected in a strain-softening material, the same process can also occur in non-softening (including strain hardening) material[1–3]. In numerical simulations, localization can occur due to boundary effects and/or variation in strength parameters[1]. In the absence of any variations in strength parameters, slight numerical artifacts can play a similar role as localization starter. In numerical simulations, localization of deformation in bands has been observed to be influenced by the numerical mesh[4–7].
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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) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| 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 ».