Lab-Scale Numerical Simulation of SAGD Process in the Presence of Top Thief Zones: A Mechanistic Study
Notice bibliographique
Résumé
Abstract There is a major concern in the steam-assisted gravity drainage (SAGD) process that the existence of thief zones such as top water and/or gas cap overlying the oil sand deposit has a detrimental effect on the oil recovery. The objective of this numerical study is to investigate the mechanisms that govern the oil and steam loss during the SAGD process in the presence of a top water zone or a gas cap. The reservoir model, STARS, developed by the Computer Modelling Group (CMG) Ltd. was first validated based on history matching of two 3-D SAGD laboratory experiments with a top water zone and a gas cap, respectively. The experiments that were designed to mimic SAGD processes in the Athabasca region were conducted at field conditions of reservoir pressure and steam injection temperature. It was found that STARS was capable of history matching the top water and gas cap experiments. Therefore, it is believed that the numerical simulation captured the major mechanism of oil movement from the oil zone into the top thief zones as observed in the experiments. Lab-scale numerical sensitivity study indicated that oil movement from the oil zone into the top thief zones occurred when a very small pressure gradient existed between the oil zone and the top thief zone (e.g. < 10 kPa/m). Higherpressure gradients resulted in more oil and steam movements into the top thief zone, less oil production and higher steam-oil ratio. Introduction There is a major concern by Alberta oil producers that the production of natural gas in association with oil sands would lower reservoir pressure, reduce oil recovery and may be prohibit the economic recovery of any oil. Alberta Department of Energy (ADOE) and Alberta Energy and Utilities Board (AEUB) initiated a series of field-scale numerical modeling studies1,2 to assess the potential applicability of the steam-assisted gravity drainage (SAGD) oil recovery process under a variety of reservoir conditions such as reservoir thickness, reservoir depth, initial pressure, oil saturation, and the presence of top water zones and gas caps. It was found that top water zones and gas caps are thief zones to SAGD process. These thief zones have a detrimental effect on SAGD recovery performance especially when the pressure in the thief zones is reduced below optimum SAGD operating pressures due to natural gas production. Movement of oil into the top water zones and gas caps is simulated to occur. The volume of this oil seems to be generally proportional to the amount of outflow from the pattern due to thickness of the top water zones/gas caps and the pressure difference between the steam chamber and the top thief zones. SAGD process costs depend on the amount of steam that flows into the top water zones and gas caps, from which no oil is produced. A case in point is the Surmont oil sands lease, which Gulf plans to develop with a SAGD pilot starting in June 1997 followed quickly by commercial development.
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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 | 0,000 |
| 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) | 0,003 | 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 ».