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Molecular Dynamics Insight into the CO 2 Flooding Mechanism in Wedge-Shaped Pores. Molecules 2022; 28:molecules28010188. [PMID: 36615381 PMCID: PMC9821883 DOI: 10.3390/molecules28010188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 12/22/2022] [Accepted: 12/23/2022] [Indexed: 12/28/2022] Open
Abstract
Because of the growing demand for energy, oil extraction under complicated geological conditions is increasing. Herein, oil displacement by CO2 in wedge-shaped pores was investigated by molecular dynamics simulation. The results showed that, for both single and double wedge-shaped models, pore Ⅱ (pore size from 3 to 8 nm) exhibited a better CO2 flooding ability than pore Ⅰ (pore size from 8 to 3 nm). Compared with slit-shaped pores (3 and 8 nm), the overall oil displacement efficiency followed the sequence of 8 nm > double pore Ⅱ > single pore Ⅱ > 3 nm > double pore Ⅰ > single pore Ⅰ, which confirmed that the exits of the wedge-shaped pores had determinant effects on CO2 enhanced oil recovery over their entrances. “Oil/CO2 inter-pore migration” and “siphoning” phenomena occurred in wedge-shaped double pores by comparing the volumes of oil/CO2 and the center of mass. The results of the interaction and radial distribution function analyses indicate that the wide inlet and outlet had a larger CO2−oil contact surface, better phase miscibility, higher interaction, and faster displacement. These findings clarify the CO2 flooding mechanisms in wedge-shaped pores and provide a scientific basis for the practical applications of CO2 flooding.
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2
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Microscopic production characteristics of tight oil in the nanopores of different CO2-affected areas from molecular dynamics simulations. Sep Purif Technol 2022. [DOI: 10.1016/j.seppur.2022.122607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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3
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Wettability reversal on oil-wet calcite surfaces: Experimental and computational investigations of the effect of the hydrophobic chain length of cationic surfactants. J Colloid Interface Sci 2022; 619:168-178. [DOI: 10.1016/j.jcis.2022.03.114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 11/18/2022]
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Zhao Y, Li W, Zhan S, Jin Z. Breakthrough pressure of oil displacement by water through the ultra-narrow kerogen pore throat from the Young-Laplace equation and molecular dynamic simulations. Phys Chem Chem Phys 2022; 24:17195-17209. [PMID: 35792334 DOI: 10.1039/d2cp01643e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
As one common unconventional reservoir, shale plays a pivotal role to compensate the depletion of conventional oil resources. There are numerous nanoscale pores and ultra-narrow pore throats (sub 2 nm) in shale media. To displace oil through ultra-narrow pore throats by water, one needs to overcome excessively-high capillary pressure. Understanding the water-oil two-phase displacement process through pore throats is critical to numerical simulation on tight/shale oil exploitation and ultimate oil recovery estimation. In this work, we use molecular dynamics simulations to investigate oil (represented by n-octane) displacement by water through a ~2 nm kerogen (represented by Type II-C kerogen) pore throat. Besides, the applicability of the Young-Laplace equation to the ultra-narrow kerogen pore throat has been assessed. We find that although the Type II-C kerogen is generally oil-wet, water has an excellent displacement efficiency without the oil film on the substrate, thanks to the hydrogen bonding formed between water and heteroatoms (such as O, N, and S) on the kerogen surface. Unlike previous studies, the capillary pressure obtained from the widely used Young-Laplace equation shows a good agreement with the breakthrough pressure obtained from MD simulations for the ∼2 nm kerogen pore throat. Our work indicates that explicitly considering intermolecular interactions as well as atomistic and molecular level characteristics is imperative to study the two-phase displacement process through ultra-narrow pore throats.
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Affiliation(s)
- Yinuo Zhao
- School of Mining and Petroleum Engineering, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Wenhui Li
- School of Mining and Petroleum Engineering, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Shiyuan Zhan
- College of Energy, Chengdu University of Technology, Chengdu 610059, China.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China
| | - Zhehui Jin
- School of Mining and Petroleum Engineering, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
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Song W, Prodanović M, Yao J, Zhang K. Nano-scale Wetting Film Impact on Multiphase Transport Properties in Porous Media. Transp Porous Media 2022. [DOI: 10.1007/s11242-022-01800-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Tetteh J, Bai S, Kubelka J, Piri M. Surfactant-induced wettability reversal on oil-wet calcite surfaces: Experimentation and molecular dynamics simulations with scaled-charges. J Colloid Interface Sci 2021; 609:890-900. [PMID: 34848057 DOI: 10.1016/j.jcis.2021.11.080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 11/03/2021] [Accepted: 11/15/2021] [Indexed: 01/29/2023]
Abstract
HYPOTHESIS Surfactant flooding is the leading approach for reversing the wettability of oil-wet carbonate reservoirs, which is critical for the recovery of the remaining oil. Combination of molecular dynamics (MD) simulations with experiments on simplified model systems can uncover the molecular mechanisms of wettability reversal and identify key molecular properties for systematic design of new, effective chemical formulations for the enhanced oil recovery. EXPERIMENTS/SIMULATIONS Wettability reversal by a series of surfactant solutions was studied experimentally using contact angle measurements on aged calcite chips, and a novel MD simulation methodology with scaled-charges that provides superior description of the ionic interactions in aqueous solutions. FINDINGS The MD simulation results were in excellent agreement with the experiments. Cationic surfactants were the most effective in reversing the calcite wettability, resulting in complete detachment of the oil from the surface. Some nonionic surfactants also altered the wettability, but to a lesser degree, while the amphoteric and anionic surfactants had no effect. From the tested cationic surfactants, the double-tailed one was the least effective, but the experiments were inconclusive due to its poor solubility. Contributions of specific interactions to the wettability reversal process and implications for the design and optimization of surfactants for the enhanced oil recovery are discussed.
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Affiliation(s)
- Julius Tetteh
- Center of Innovation for Flow Through Porous Media, Department of Petroleum Engineering, University of Wyoming, Laramie, WY 82071, United States
| | - Shixun Bai
- Center of Innovation for Flow Through Porous Media, Department of Petroleum Engineering, University of Wyoming, Laramie, WY 82071, United States
| | - Jan Kubelka
- Center of Innovation for Flow Through Porous Media, Department of Petroleum Engineering, University of Wyoming, Laramie, WY 82071, United States.
| | - Mohammad Piri
- Center of Innovation for Flow Through Porous Media, Department of Petroleum Engineering, University of Wyoming, Laramie, WY 82071, United States
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Ali M, Yekeen N, Pal N, Keshavarz A, Iglauer S, Hoteit H. Influence of organic molecules on wetting characteristics of mica/H 2/brine systems: Implications for hydrogen structural trapping capacities. J Colloid Interface Sci 2021; 608:1739-1749. [PMID: 34742087 DOI: 10.1016/j.jcis.2021.10.080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/08/2021] [Accepted: 10/14/2021] [Indexed: 11/19/2022]
Abstract
HYPOTHESIS Actualization of the hydrogen (H2) economy and decarbonization goals can be achieved with feasible large-scale H2 geo-storage. Geological formations are heterogeneous, and their wetting characteristics play a crucial role in the presence of H2, which controls the pore-scale distribution of the fluids and sealing capacities of caprocks. Organic acids are readily available in geo-storage formations in minute quantities, but they highly tend to increase the hydrophobicity of storage formations. However, there is a paucity of data on the effects of organic acid concentrations and types on the H2-wettability of caprock-representative minerals and their attendant structural trapping capacities. EXPERIMENT Geological formations contain organic acids in minute concentrations, with the alkyl chain length ranging from C4 to C26. To fully understand the wetting characteristics of H2 in a natural geological picture, we aged mica mineral surfaces as a representative of the caprock in varying concentrations of organic molecules (with varying numbers of carbon atoms, lignoceric acid C24, lauric acid C12, and hexanoic acid C6) for 7 days. To comprehend the wettability of the mica/H2/brine system, we employed a contact-angle procedure similar to that in natural geo-storage environments (25, 15, and 0.1 MPa and 323 K). FINDINGS At the highest investigated pressure (25 MPa) and the highest concentration of lignoceric acid (10-2 mol/L), the mica surface became completely H2 wet with advancing (θa= 106.2°) and receding (θr=97.3°) contact angles. The order of increasing θa and θr with increasing organic acid contaminations is as follows: lignoceric acid > lauric acid > hexanoic acid. The results suggest that H2 gas leakage through the caprock is possible in the presence of organic acids at higher physio-thermal conditions. The influence of organic contamination inherent at realistic geo-storage conditions should be considered to avoid the overprediction of structural trapping capacities and H2 containment security.
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Affiliation(s)
- Muhammad Ali
- Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia; Western Australia School of Mines, Minerals, Energy and Chemical Engineering, Curtin University, Kensington 6151, Western Australia, Australia.
| | - Nurudeen Yekeen
- Department of Chemical & Petroleum Engineering, Faculty of Engineering, Technology and Built Environment, UCSI University, 56000 Kuala Lumpur, Malaysia
| | - Nilanjan Pal
- Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
| | - Alireza Keshavarz
- School of Engineering, Edith Cowan University, Joondalup 6027, WA, Australia
| | - Stefan Iglauer
- School of Engineering, Edith Cowan University, Joondalup 6027, WA, Australia
| | - Hussein Hoteit
- Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia.
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Banerjee T, Samanta A. Chemical computational approaches for optimization of effective surfactants in enhanced oil recovery. PHYSICAL SCIENCES REVIEWS 2021. [DOI: 10.1515/psr-2020-0098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Abstract
The surfactant flooding becomes an attractive method among several Enhanced Oil Recovery (EOR) processes to improve the recovery of residual oil left behind in the reservoir after secondary oil recovery process. The designing of a new effective surfactant is a comparatively complex and often time consuming process as well as cost-effective due to its dependency on the crude oil and reservoir properties. An alternative chemical computational approach is focused in this article to optimize the performance of effective surfactant system for EOR. The molecular dynamics (MD), dissipative particle dynamics (DPD) and density functional theory (DFT) simulations are mostly used chemical computational approaches to study the behaviour in multiple phase systems like surfactant/oil/brine. This article highlighted a review on the impact of surfactant head group structure on oil/water interfacial property like interfacial tensions, interface formation energy, interfacial thickness by MD simulation. The effect of entropy in micelle formation has also discussed through MD simulation. The polarity, dipole moment, charge distribution and molecular structure optimization have been illustrated by DFT. A relatively new coarse-grained method, DPD is also emphasized the phase behaviour of surfactant/oil/brine as well as polymer-surfactant complex system.
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Affiliation(s)
- Tandrima Banerjee
- Department of Chemical Sciences , Indian Institute of Science Education and Research (IISER) Kolkata , West Bengal 741246 , India
| | - Abhijit Samanta
- School of Engineering and Applied Sciences , The Neotia University , Sarisha , West Bengal 743368 , India
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Kubelka J, Bai S, Piri M. Effects of Surfactant Charge and Molecular Structure on Wettability Alteration of Calcite: Insights from Molecular Dynamics Simulations. J Phys Chem B 2021; 125:1293-1305. [PMID: 33475371 DOI: 10.1021/acs.jpcb.0c10361] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Wettability alteration of oil-wet calcite by surfactants was studied by means of molecular dynamics (MD) simulations. The simulations use the recently developed model for positively charged calcite surface, whose oil-wet state originates from binding of negatively charged carboxylate molecules contained in the oil, consistently with the bulk of the available experimental data. The ability to alter the surface wettability, which can be directly quantified by the release of the surface-bound carboxylates, is tested for nine different surfactants of all charge types-cationic, anionic, nonionic, and zwitterionic-and compared to that of brine. It was found that only the cationic surfactants are able to detach the organic carboxylates more efficiently than brine, while the neutral and anionic surfactants do not seem to have any measurable effect on the wettability. The outperformance of the cationic surfactants is generally consistent with the majority of previously published experimental observations. The data also point toward a consistently better performance of single-tailed cationic surfactants over the two-tailed structure. Molecular mechanism of the wettability alteration by different types of surfactants is discussed, along with the implications of the results for the design of new surfactant formulations for the enhanced oil recovery.
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Affiliation(s)
- Jan Kubelka
- Department of Chemical and Petroleum Engineering, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, United States
| | - Shixun Bai
- Department of Chemical and Petroleum Engineering, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, United States
| | - Mohammad Piri
- Department of Chemical and Petroleum Engineering, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, United States
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Yekeen N, Padmanabhan E, Sevoo TA, Kanesen KA, Okunade OA. Wettability of rock/CO2/brine systems: A critical review of influencing parameters and recent advances. J IND ENG CHEM 2020. [DOI: 10.1016/j.jiec.2020.03.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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12
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Gao J, Zhang G, Wang L, Xue X, Ding L, Li X, Lai X, Huang C. Properties of a novel imbibition polymer with ultra-high wetting ability as a fracturing fluid system. NEW J CHEM 2020. [DOI: 10.1039/c9nj03515j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A fracturing fluid with wetting ability was obtained by a crosslinking strategy. The ultra-high wettability transformed a sandstone surface from oil-wet to water-wet.
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Affiliation(s)
- Jinhao Gao
- Shaanxi Key Laboratory of Chemical Additives for Industry
- Shaanxi University of Science and Technology
- Xi'an
- China
| | - Guanghua Zhang
- Shaanxi Key Laboratory of Chemical Additives for Industry
- Shaanxi University of Science and Technology
- Xi'an
- China
| | - Lei Wang
- Shaanxi Key Laboratory of Chemical Additives for Industry
- Shaanxi University of Science and Technology
- Xi'an
- China
| | - Xiaojia Xue
- National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields
- Changging Oil Field
- PetroChina
- China
| | - Li Ding
- National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields
- Changging Oil Field
- PetroChina
- China
| | - Xianwen Li
- National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields
- Changging Oil Field
- PetroChina
- China
| | - Xiaojuan Lai
- Shaanxi Key Laboratory of Chemical Additives for Industry
- Shaanxi University of Science and Technology
- Xi'an
- China
| | - Chuanqing Huang
- Shaanxi Key Laboratory of Chemical Additives for Industry
- Shaanxi University of Science and Technology
- Xi'an
- China
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13
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Zhang Y, Fang T, Li R, Yan Y, Guo W, Zhang J. Molecular insight into the oil charging mechanism in tight reservoirs. Chem Eng Sci 2020. [DOI: 10.1016/j.ces.2019.115297] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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14
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15
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Effect of Nanoparticles on Spontaneous Imbibition of Water into Ultraconfined Reservoir Capillary by Molecular Dynamics Simulation. ENERGIES 2017. [DOI: 10.3390/en10040506] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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16
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Roshan H, Al-Yaseri A, Sarmadivaleh M, Iglauer S. On wettability of shale rocks. J Colloid Interface Sci 2016; 475:104-111. [DOI: 10.1016/j.jcis.2016.04.041] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 04/24/2016] [Accepted: 04/26/2016] [Indexed: 11/25/2022]
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17
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Sedghi M, Piri M, Goual L. Atomistic Molecular Dynamics Simulations of Crude Oil/Brine Displacement in Calcite Mesopores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:3375-3384. [PMID: 27010399 DOI: 10.1021/acs.langmuir.5b04713] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Unconventional reservoirs such as hydrocarbon-bearing shale formations and ultratight carbonates generate a large fraction of oil and gas production in North America. The characteristic feature of these reservoirs is their nanoscale porosity that provides significant surface areas between the pore walls and the occupying fluids. To better assess hydrocarbon recovery from these formations, it is crucial to develop an improved insight into the effects of wall-fluid interactions on the interfacial phenomena in these nanoscale confinements. One of the important properties that controls the displacement of fluids inside the pores is the threshold capillary pressure. In this study, we present the results of an integrated series of large-scale molecular dynamics (MD) simulations performed to investigate the effects of wall-fluid interactions on the threshold capillary pressures of oil-water/brine displacements in a calcite nanopore with a square cross section. Fully atomistic models are utilized to represent crude oil, brine, and calcite in order to accommodate electrostatic interactions and H-bonding between the polar molecules and the calcite surface. To this end, we create mixtures of various polar and nonpolar organic molecules to better represent the crude oil. The interfacial tension between oil and water/brine and their contact angle on calcite surface are simulated. We study the effects of oil composition, water salinity, and temperature and pressure conditions on these properties. The threshold capillary pressure values are also obtained from the MD simulations for the calcite nanopore. We then compare the MD results against those generated using the Mayer-Stowe-Princen (MSP) method and explain the differences.
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Affiliation(s)
- Mohammad Sedghi
- Department of Petroleum Engineering, University of Wyoming , 1000 East University Avenue, Laramie, Wyoming 82071, United States
| | - Mohammad Piri
- Department of Petroleum Engineering, University of Wyoming , 1000 East University Avenue, Laramie, Wyoming 82071, United States
| | - Lamia Goual
- Department of Petroleum Engineering, University of Wyoming , 1000 East University Avenue, Laramie, Wyoming 82071, United States
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Welch WRW, Piri M. Pore diameter effects on phase behavior of a gas condensate in graphitic one-and two-dimensional nanopores. J Mol Model 2016; 22:22. [PMID: 26733485 DOI: 10.1007/s00894-015-2894-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/21/2015] [Indexed: 11/28/2022]
Abstract
Molecular dynamics (MD) simulations were performed on a hydrocarbon mixture representing a typical gas condensate composed mostly of methane and other small molecules with small fractions of heavier hydrocarbons, representative of mixtures found in tight shale reservoirs. The fluid was examined both in bulk and confined to graphitic nano-scale slits and pores. Numerous widths and diameters of slits and pores respectively were examined under variable pressures at 300 K in order to find conditions in which the fluid at the center of the apertures would not be affected by capillary condensation due to the oil-wet walls. For the bulk fluid, retrograde phase behavior was verified by liquid volumes obtained from Voronoi tessellations. In cases of both one and two-dimensional confinement, for the smallest apertures, heavy molecules aggregated inside the pore space and compression of the gas outside the solid structure lead to decreases in density of the confined fluid. Normal density/pressure relationships were observed for slits having gaps of above 3 nm and pores having diameters above 6 nm. At 70 bar, the minimum gap width at which the fluid could pass through the center of slits without condensation effects was predicted to be 6 nm and the corresponding diameter in pores was predicted to be 8 nm. The models suggest that in nanoscale networks involving pores smaller than these limiting dimensions, capillary condensation should significantly impede transmission of natural gases with similar composition.
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Affiliation(s)
- William R W Welch
- Department of Petroleum Engineering, University of Wyoming, 1000 E University Avenue, Dept. 3295, Laramie, Wyoming, 82071, USA.
| | - Mohammad Piri
- Department of Petroleum Engineering, University of Wyoming, 1000 E University Avenue, Dept. 3295, Laramie, Wyoming, 82071, USA
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Gruener S, Wallacher D, Greulich S, Busch M, Huber P. Hydraulic transport across hydrophilic and hydrophobic nanopores: Flow experiments with water and n-hexane. Phys Rev E 2016; 93:013102. [PMID: 26871150 DOI: 10.1103/physreve.93.013102] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Indexed: 06/05/2023]
Abstract
We experimentally explore pressure-driven flow of water and n-hexane across nanoporous silica (Vycor glass monoliths with 7- or 10-nm pore diameters, respectively) as a function of temperature and surface functionalization (native and silanized glass surfaces). Hydraulic flow rates are measured by applying hydrostatic pressures via inert gases (argon and helium, pressurized up to 70 bar) on the upstream side in a capacitor-based membrane permeability setup. For the native, hydrophilic silica walls, the measured hydraulic permeabilities can be quantitatively accounted for by bulk fluidity provided we assume a sticking boundary layer, i.e., a negative velocity slip length of molecular dimensions. The thickness of this boundary layer is discussed with regard to previous capillarity-driven flow experiments (spontaneous imbibition) and with regard to velocity slippage at the pore walls resulting from dissolved gas. Water flow across the silanized, hydrophobic nanopores is blocked up to a hydrostatic pressure of at least 70 bar. The absence of a sticking boundary layer quantitatively accounts for an enhanced n-hexane permeability in the hydrophobic compared to the hydrophilic nanopores.
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Affiliation(s)
- Simon Gruener
- Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany and Sorption and Permeation Laboratory, BASF SE, D-67056 Ludwigshafen, Germany
| | - Dirk Wallacher
- Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany and Department Sample Environments, Helmholtz-Centre Berlin for Energy and Materials, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
| | - Stefanie Greulich
- Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany
| | - Mark Busch
- Institute of Materials Physics and Technology, Eißendorfer Str. 42, D-21073 Hamburg-Harburg, Germany
| | - Patrick Huber
- Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany and Institute of Materials Physics and Technology, Eißendorfer Str. 42, D-21073 Hamburg-Harburg, Germany
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