Wettability Alteration during Low-Salinity Waterflooding and the Relevance of Divalent Ions in This Process
Notice bibliographique
Résumé
From laboratory and field test results, it is now largely agreed that reducing the overall salinity, especially the concentration of divalent ions of the injected water, can markedly improve the oil recovery. However, as a result of the complexity of the crude oil–brine–rock (COBR) system, there is no clear explanation of why the divalent cations (Ca 2+ ) are of major significance in a low-salinity water effect (LSWE). In the present paper, spontaneous imbibition, ζ-potential measurements, static adsorption/desorption of benzoic acid (BA) onto crushed Berea, and BA self-assembled layers on silica wafer have been performed to correlate macroscopic wettability alteration during low-saline water flood with the microscopic release of the hydrophobic layers (organic acid layers) on mineral surfaces and explain the relevance of active cations (Ca 2+ ) in this process, thereby providing a better understanding of the underlying mechanisms of a LSWE. Spontaneous imbibition results show that initial wettability of the COBR system was dominantly controlled by the initial concentration of Ca 2+ rather than Na + in brine; i.e., the initial wettability changed to be more oil-wet with an increasing concentration of CaCl 2 in initial water, while changing the concentration of NaCl in initial water had little effect on initial wettability. Moreover, reducing salinity of imbibing brine can outstandingly improve oil recovery of cores aged by CaCl 2 brine, whereas no obvious enhanced oil recovery (EOR) by low-salinity water was observed for cores aged by NaCl brine. Decreasing the concentration of either CaCl 2 or NaCl brine was able to make the oil/brine and brine/rock interfaces become less positively charged or even more negatively charged, observed by ζ-potential measurements, resulting in increased electrostatic repulsive forces between the oil/brine and brine/rock interfaces. These results suggest that the anionic groups of organic acid from crude oil, such as carboxylate, adsorb onto negatively charged mineral surfaces mainly through calcium bridges instead of van der Waals forces or sodium bridges and reducing salinity is able to increase the electrostatic repulsive forces between mineral surfaces and carboxylate groups and then break calcium bridges to change the wettability of the rock surface to be less oil-wet, and as a result, EOR occurs. These suggestions were supported by the static adsorption/desorption studies and self-assembly experiments. After sorption to crushed Berea, the varied BA concentration in the supernatant analyzed by total organic carbon (TOC) reveals that the presence of the background electrolyte Ca 2+ largely enhanced sorption in comparison to Na + . Lowering salinity was able to desorb BA from crushed Berea. Field emission scanning electron microscopy (FESEM) was used to obtain the microchemical composition and morphology of the wafer surface interacted with BA under different ionic strengths and solution cations (Ca 2+ and Na + ). Ca 2+ ions were found to enhance the adsorption of BA self-assembled layers on a silica wafer compared to Na +, which directly demonstrates that BA molecules mainly self-assemble on SiO 2 by calcium bridges rather than sodium bridges or van der Waals forces. The BA self-assembled layers were released after immersing organo-wafer into deionized water.
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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) | 0,000 | 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 ».