Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions
Enhanced oil recovery (EOR) via CO<sub>2</sub> flooding is a promising strategy for improving hydrocarbon recovery and carbon sequestration, yet the influence of pH on solid–liquid interfacial interactions in quartz-dominated reservoirs remains poorly understood. This study employs molec...
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2025-07-01
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| author | Xinwang Song Yang Guo Yanchang Chen Shiling Yuan |
| author_facet | Xinwang Song Yang Guo Yanchang Chen Shiling Yuan |
| author_sort | Xinwang Song |
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| description | Enhanced oil recovery (EOR) via CO<sub>2</sub> flooding is a promising strategy for improving hydrocarbon recovery and carbon sequestration, yet the influence of pH on solid–liquid interfacial interactions in quartz-dominated reservoirs remains poorly understood. This study employs molecular dynamics (MD) simulations to investigate the pH-dependent adsorption behavior of crude oil components on quartz surfaces and its impact on CO<sub>2</sub> displacement mechanisms. Three quartz surface models with varying ionization degrees (0%, 9%, 18%, corresponding to pH 2–4, 5–7, and 7–9) were constructed to simulate different pH environments. The MD results reveal that aromatic hydrocarbons exhibit significantly stronger adsorption on quartz surfaces at high pH, with their maximum adsorption peak increasing from 398 kg/m<sup>3</sup> (pH 2–4) to 778 kg/m<sup>3</sup> (pH 7–9), while their alkane adsorption peaks decrease from 764 kg/m<sup>3</sup> to 460 kg/m<sup>3</sup>. This pH-dependent behavior is attributed to enhanced cation–π interactions that are facilitated by Na<sup>+</sup> ion aggregation on negatively charged quartz surfaces at high pH, which form stable tetrahedral configurations with aromatic molecules and surface oxygen ions. During CO<sub>2</sub> displacement, an adsorption–stripping–displacement mechanism was observed: CO<sub>2</sub> first forms an adsorption layer on the quartz surface, then penetrates the oil phase to induce the detachment of crude oil components, which are subsequently displaced by pressure. Although high pH enhances the Na<sup>+</sup>-mediated weakening of oil-surface interactions, which leads to a 37% higher diffusion coefficient (8.5 × 10<sup>−5</sup> cm<sup>2</sup>/s vs. 6.2 × 10<sup>−5</sup> cm<sup>2</sup>/s at low pH), the tighter packing of aromatic molecules at high pH slows down the displacement rate. This study provides molecular-level insights into pH-regulated adsorption and CO<sub>2</sub> displacement processes, highlighting the critical role of the surface charge and cation–π interactions in optimizing CO<sub>2</sub>-EOR strategies for quartz-rich reservoirs. |
| format | Article |
| id | doaj-art-027ab82038404d35943e812edabfca14 |
| institution | Kabale University |
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| language | English |
| publishDate | 2025-07-01 |
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| series | Molecules |
| spelling | doaj-art-027ab82038404d35943e812edabfca142025-08-20T03:32:15ZengMDPI AGMolecules1420-30492025-07-013014299910.3390/molecules30142999Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH ConditionsXinwang Song0Yang Guo1Yanchang Chen2Shiling Yuan3Shandong Key Laboratory of Green Electricity & Hydrogen Science and Technology, School of Chemical Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying 257061, ChinaShandong Key Laboratory of Green Electricity & Hydrogen Science and Technology, School of Chemical Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying 257061, ChinaShandong Key Laboratory of Green Electricity & Hydrogen Science and Technology, School of Chemical Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying 257061, ChinaShandong Key Laboratory of Green Electricity & Hydrogen Science and Technology, School of Chemical Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying 257061, ChinaEnhanced oil recovery (EOR) via CO<sub>2</sub> flooding is a promising strategy for improving hydrocarbon recovery and carbon sequestration, yet the influence of pH on solid–liquid interfacial interactions in quartz-dominated reservoirs remains poorly understood. This study employs molecular dynamics (MD) simulations to investigate the pH-dependent adsorption behavior of crude oil components on quartz surfaces and its impact on CO<sub>2</sub> displacement mechanisms. Three quartz surface models with varying ionization degrees (0%, 9%, 18%, corresponding to pH 2–4, 5–7, and 7–9) were constructed to simulate different pH environments. The MD results reveal that aromatic hydrocarbons exhibit significantly stronger adsorption on quartz surfaces at high pH, with their maximum adsorption peak increasing from 398 kg/m<sup>3</sup> (pH 2–4) to 778 kg/m<sup>3</sup> (pH 7–9), while their alkane adsorption peaks decrease from 764 kg/m<sup>3</sup> to 460 kg/m<sup>3</sup>. This pH-dependent behavior is attributed to enhanced cation–π interactions that are facilitated by Na<sup>+</sup> ion aggregation on negatively charged quartz surfaces at high pH, which form stable tetrahedral configurations with aromatic molecules and surface oxygen ions. During CO<sub>2</sub> displacement, an adsorption–stripping–displacement mechanism was observed: CO<sub>2</sub> first forms an adsorption layer on the quartz surface, then penetrates the oil phase to induce the detachment of crude oil components, which are subsequently displaced by pressure. Although high pH enhances the Na<sup>+</sup>-mediated weakening of oil-surface interactions, which leads to a 37% higher diffusion coefficient (8.5 × 10<sup>−5</sup> cm<sup>2</sup>/s vs. 6.2 × 10<sup>−5</sup> cm<sup>2</sup>/s at low pH), the tighter packing of aromatic molecules at high pH slows down the displacement rate. This study provides molecular-level insights into pH-regulated adsorption and CO<sub>2</sub> displacement processes, highlighting the critical role of the surface charge and cation–π interactions in optimizing CO<sub>2</sub>-EOR strategies for quartz-rich reservoirs.https://www.mdpi.com/1420-3049/30/14/2999oil adsorption behaviorCO<sub>2</sub> floodingpH effectmolecular dynamics simulationquartz surfaceinterfacial interactions |
| spellingShingle | Xinwang Song Yang Guo Yanchang Chen Shiling Yuan Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions Molecules oil adsorption behavior CO<sub>2</sub> flooding pH effect molecular dynamics simulation quartz surface interfacial interactions |
| title | Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions |
| title_full | Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions |
| title_fullStr | Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions |
| title_full_unstemmed | Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions |
| title_short | Mechanistic Study of Oil Adsorption Behavior and CO<sub>2</sub> Displacement Mechanism Under Different pH Conditions |
| title_sort | mechanistic study of oil adsorption behavior and co sub 2 sub displacement mechanism under different ph conditions |
| topic | oil adsorption behavior CO<sub>2</sub> flooding pH effect molecular dynamics simulation quartz surface interfacial interactions |
| url | https://www.mdpi.com/1420-3049/30/14/2999 |
| work_keys_str_mv | AT xinwangsong mechanisticstudyofoiladsorptionbehaviorandcosub2subdisplacementmechanismunderdifferentphconditions AT yangguo mechanisticstudyofoiladsorptionbehaviorandcosub2subdisplacementmechanismunderdifferentphconditions AT yanchangchen mechanisticstudyofoiladsorptionbehaviorandcosub2subdisplacementmechanismunderdifferentphconditions AT shilingyuan mechanisticstudyofoiladsorptionbehaviorandcosub2subdisplacementmechanismunderdifferentphconditions |