Experimental Study of Extent and Rate of Gravity Drainage of Oil From Matrix into Fractures in Presence of Miscible and Immiscible CO2
Notice bibliographique
Résumé
Abstract Gravity drainage is the dominant production mechanism in fractured reservoirs, where injection of hydrocarbon gases is believed to improve oil recovery. This paper presents the results of an experimental study of the effect of injecting CO2 into fractured media and its influence on the performance of gravity drainage and ultimate oil production. Both miscible (i.e. high pressure) and immiscible (i.e. low pressure) schemes for CO2 are investigated in this study. The results obtained from these experiments are used to compare the effect of miscible versus immiscible gases, i.e. CO2, on gravity drainage. For these experiments a special stain steel holder was designed allowing an open space around a core of 30 cm long and 5 cm in diameter, simulating a matrix with surrounding fractures. Carbon dioxide and normal decane were used as solvent and oil, respectively. While all experiments were conducted at constant temperature of 35 °C, six series of experiments were carried out at 250, 500, 750, 1000, 1250, and 1500 psi. A high pressure calibrated glass-gauge was connected to the bottom of the fractured media model allowing the produced oil be collected and measured continuously under the pressure and temperature conditions of the experiments. Analyzing the results show that injecting CO2 at higher pressures improves the recovery factor of gravity drainage mechanism in fractured media, significantly. Introduction CO2 flooding has been considered an inefficient process for enhancing oil recovery from naturally fractured reservoir. This is mainly due early gas breakthrough through fractures and very low oil recovery. However, miscible CO2 injection can be used to improve oil recovery in such reservoirs. In fractured reservoirs, the main production mechanism is gravity drainage. The performance of this process in naturally fractured reservoirs is a function of a series of parameters such as fracture-matrix geometry, size, matrix-fracture flow interaction, and so on (1). In the case of application of miscible CO2 both viscosity and density of oil and injected CO2 play important roles. At highpressure conditions, the density of liquid CO2 is about the same and sometimes larger than the oil in-place (2). Therefore, since fractures are filled with dense CO2 during miscible CO2 injection, oil recovery may be reduced due to the presence of denser solvent around the matrix. However, significant reduction in interfacial tension and capillary pressure would lead to a better ultimate oil recovery (3). Several studies show that viscosity ratio, density differences, matrix permeability, and production rate have significant impact on oil recovery by miscible CO2 in fractured environments (4,5). Firoozabadi and Markeset used nC14 and nC10 to study miscible displacement in a fractured medium (6). Both of these solvents were liquid at room conditions, which leads to first contact miscible conditions between the solvent and oil in the matrix. In another study Jamshidnezhad et. al showed that displacement rate has a great impact on oil recovery from fractured reservoir under miscible conditions (7). It is clear that in a miscible displacement process in fractured reservoirs, oil is swept completely from fractures during the early stages of production.
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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) | 0,000 | 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 ».