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The impact of confined spaces on the phase transition of water or electrolyte solutions has garnered considerable interest due to their widespread occurrence in natural processes and technological applications. [1-3] Specifically, phenomena such as freezing, melting, and vapor condensation have been extensively studied. Recently, there has been growing attention towards the phase transition of...
Nanoporous materials provide high surface area per unit mass and are capable of fluids adsorption. While the measurements of overall amount of fluid adsorbed by a nanoporous sample are straightforward, probing the spatial distribution of fluids is non-trivial. For macro-porous media the effect of partial saturation on acoustic properties is described by the theory of poroelasticity.
To test...
The pressure oscillation method is a widely employed technique for measuring the permeability of time-varying and tight porous media. The previous analytical solution for permeability calculation neglects the unsteady-state condition of the slip effect, and the application of the Klinkenberg correction lacks theoretical support. Existing permeability calculations rely on the periodic part, and...
This study quantifies the pore structures and reactive flow capacity of basalt rocks, specifically a range of flow top (vesicular) and seal basalt samples from Newberry Volcano drill core (Oregon, USA). Dissolution and precipitation reactions in basalts and other mafic and ultramafic rocks (silicates rich in Mg, Ca, and Fe) are the foundation for carbon mineralization, in situ mining, and...
Shale oil, widely distributed in organic (i.e., kerogen) nanopores, is playing an ever-increasing role in addressing the global energy crisis, but is faced with challenges of low recovery efficiency due to well-developed nanopores. It is believed that the pore size distribution of kerogen is in the range of several angstroms to tens of nanometers (AAPG bulletin 96 (6): 1099-1119). In such a...
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Geological storage of acidic gases can reduce atmospheric emissions of CO2 and H2S, thus serving as a critical part of low-carbon energy systems. Depleted shale gas reservoirs are good storage candidates owing to their intrinsic gas storage capacity. However, shales exhibit complex structural characteristics and abundant micro- and nano-scale pores, where gases primarily...
CO2 huff-n-puff is a potential promising approach for enhanced recovery and sequestration of CO2 in shale reservoirs. It is of great practical significance to understand the CO2 huff-n-puff mechanism from a microscopic point of view. Here, we investigate three stages of CO2 huff-n-puff promoting shale oil mobilization from organic-inorganic nanopores by molecular dynamics simulation. We show...
Understanding the occurrence and flow mechanisms of shale oil in nanopores, as well as the impact mechanisms of fluids on solid deformation, is crucial for advancing our comprehension of fluid behavior in porous media. Prior neglect of factors such as the multi-component characteristics of shale oil, the properties of real shale nanopore walls, and nanopore flexibility has resulted in...
The gas-liquid two-phase flow in rough nanopores plays a crucial role in shale gas extraction. To deeply understand the flow mechanisms, molecular dynamics simulation (MDS) method is often employed to simulate fluid flow in nanoscale channels. However, current researches on two-phase flow at the nanoscale have mainly focused on smooth channels. In addition, accurate simulation of the rock wall...
In the background of the strong oil wettability and low production by water flooding in carbonate reservoirs, low salinity water containing sulfate ions and nanoparticles can significantly change the surface wettability of carbonate rocks and thus increase the sweeping area, however, the absorption and desorption mechanisms of the oil film in the carbonate rock surface remain unclear. In this...
A contrast-variation technique in small-angle neutron scattering (CV-SANS) is employed to investigate the interfacial chemistry of shale oil reservoirs using reagents that span a range of polarities, including water, toluene, and dimethyl methanamide. Through five different experimental strategies, the work demonstrates a modification of shale wettability, ranging from enhancement, weakening,...
The key characteristics of complex oil and gas reservoirs include high heterogeneity in the porous space, ultra-low permeability resulting from the nanoscale dimensions of pores, and the presence of solid insoluble organic compounds in the rock. These factors complicate the application of existing physical and mathematical flow models with sufficient accuracy. This causes challenges in...
Shale oil and gas primarily exist in nanoscale pore-fracture networks. Despite of the large resources of the oil shale and low-medium mature shale, limited removable hydrocarbon and extremely low permeability due to limited pores restrict in the development of those unconventional resources. Therefore, different pyrolysis technologies, such as in situ conversion pyrolysis, superheated steam,...
The reservoir space of shale series is mainly composed of micro and nano pores. It is significance to carry out the occurrence characteristics and quantitative evaluation of shale oil with micro- nano pores for the study of shale oil rich and integrated reservoirs. In 2020, Well Ping’ an 1, located in the northeastern region of Sichuan Basin, achieved a high yield of 100 tons in Jurassic...
Wood is extensively applied in various fields such as construction, tooling, sculpture, boat building. The water content within wood plays a crucial role in influencing its performance across different contexts. For example, a large portion of water must be removed from wet or green (fresh cut) wood to mitigate further dimensional variations under varying humidity conditions. In this context,...
Fluids can induce solid adsorption and swelling in porous materials when they infiltrate pores. For example, alkaline liquids created after water mixing with alkali metals can react with minerals like quartz or feldspar and form a new substance called alkali calcium silicate hydrate. Fluid flow facilitates the damage of concrete as this new substance can swell upon adsorbing water and crack...
Discotic ionic liquid crystals (DILCs) consist of self-assembled superdiscs of cations and anions that spontaneously stack in linear columns with high one-dimensional ionic and electronic charge mobility, making them prominent model systems for functional soft matter. Compared to classical non-ionic discotic liquid crystals (DLCs), many novel liquid crystalline structures with a unique...
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Coal is a porous medium material with a highly developed pore network inside. Nanopores dominate gas adsorption and transport behavior in geological reservoirs. The fractal nanopore structure of anthracite from the Qinshui Basin were characterized using synchrotron radiation small angle X-ray scattering (SAXS). Based on the fractal theory of SAXS, the fractal characteristics of...
Microscopic pore structure (both geometry and connectivity) characteristics control fluid flow and hydrocarbon movement in shale oil reservoirs. Considering the uniquely wide spectrum of pore sizes (nm to sub-mm), microscale mixed wettability, as well as the interplay of pore structure and wettability in organic-rich shale oil reservoirs, this work presents various approaches to quantifying...
The study of electrolyte solutions in confined geometries is crucial for developing energy storage devices and water purification systems. One challenge in this field is accurate modeling ion behavior while considering the interplay between ion-specific effects and electrostatic interactions. Although self-consistent field theory enables the simulation of ionic fluids, it overlooks several...
In order to investigate the influence of movable oil on the pore structure of various shale types, this study systematically selected 19 shale samples from Well X in the Mahu Sag of the Junggar Basin. Initially, X-ray diffraction (XRD) analysis was conducted to classify the shale samples. Subsequently, the geochemical properties and pore structures of the samples, both pre and post oil...
Shale is attracting more and more attention owing to the huge hydrocarbon resources. However, the large number of nanopores and the multiscale pore structure pose great challenges in accurately characterizing the transport behavior of crude oil within the shale matrix. Although most studies suggested that the classical Darcy’s law breakdown in the shale matrix, there is a great controversy on...
Recent developments in unconventional oil and gas reservoirs such as shale gas have brought the pore structures and gas adsorption characteristics into focus. Traditional models, such as the original Simplified Local-Density (SLD) model with a slit-shaped pore, fall short in accurately describing gas adsorption in these reservoirs due to the presence of various carbon pore geometries,...
Shale contains abundant multi-component nanopore spaces with different wettability. Water flow in multi-component nanoporous systems is still unclear due to the effects of complex pore throat topology and heterogeneous wettability, which limits knowledge of hydraulic fracturing for enhanced hydrocarbon recovery. This work reconstructs single-component (i.e. clay, organic, inorganic matter) and...
Ion diffusion within clays is a fundamental process related to contaminant transport in groundwater and radionuclide migration in the context of nuclear waste disposal. Montmorillonite, one of the predominant minerals within bentonitic clays, exhibits distinguished physicochemical properties such as the ability to absorb water and ions, accompanied by underlying swelling. This behavior is...
This study presents a novel multi-scale approach for assessing the accessibility of shale oil in cores. By using FIB-SEM equipment to build digital core, watershed and maximum ball method to extract pore size and shape factor. Then molecular simulation is used to study the availability of shale oil in individual pores with different shapes and radii. Finally, combining the results of the...
Sedimentary rock is wet in situ and generally occurs at depths in the subsurface where pores are saturated with water and hydrocarbons. The competitive adsorption of water and oil in nanopores of shales is believed to influence the dynamic configurations of fluids, and therefore their wetting and displacement behaviors and ultimately oil production. But its nature is poorly understood due to...
The observation of a cavitation bubble forming as a nano-scale spherical surface detached from a flat substrate unveiled complexities in capturing the cavitation pattern, hindered by existing methodological constraints. To decode the molecular dynamics and detailed morphology underlying this phenomenon, the study applies molecular dynamics (MD) simulations. This investigation mapped the onset...
In the field of oil recovery and other industrial applications, the significance of an accurate and efficient model for porous media cannot be overstated. At present, most of the macroscopic models for the gas flow in porous media at a high Knudsen number are only investigated under pressure gradient. What’s more, the thermal effect becomes prominent in a single tube as the rarefication degree...
Fluid phase behavior in shale nanopores has become a hot topic in recent years. But, most of the current investigations are based on a smooth porewall assumption. Actually, for such small-scale pores in shale, a serious porewall heterogeneity has been observed, which has been confirmed in many experimental observations.
In this paper, the methods of N2 adsorption and desorption measurement,...
CO2 miscible injection holds tremendous potential for enhancing tight oil recovery, where achieving the minimum miscibility pressure (MMP) is crucial. The adsorption of CO2 and oil in nanopores affects the CO2-oil MMP in tight reservoirs, necessitating the precise calculations of nanoscale MMP and a comprehensive understanding of influencing factors. In this work, we employed a modified...
