Displacement Mechanisms Research Articles

Modeling cell crawling strategies with a bistable model: From amoeboid to fan-shaped cell motion

Eukaryotic cell motility involves a complex network of interactions between biochemical components and mechanical processes. The cell employs this network to polarize and induce shape changes that give rise to membrane protrusions and retractions, ultimately leading to locomotion of the entire cell body. The combination of a nonlinear reaction–diffusion model of cell polarization, noisy bistable kinetics, and a dynamic phase field for the cell shape permits us to capture the key features of this complex system to investigate several motility scenarios, including amoeboid and fan-shaped forms as well as intermediate states with distinct displacement mechanisms. We compare the numerical simulations of our model to live cell imaging experiments of motile Dictyostelium discoideum cells under different developmental conditions. The dominant parameters of the mathematical model that determine the different motility regimes are identified and discussed.

How N2 injection improves the hydrocarbon recovery of CO2 HnP: An NMR study on the fluid displacement mechanisms

CO2 HnP, despite its promised potential and societal support for potential carbon negativity, suffered from the elevated cost; its application is limited in scale at the time of this writing. Practitioners had explored a mixture of CO2 with N2 as the treatment gas to reduce the cost and improve recovery. Nevertheless, these efforts are currently thwarted by a lack of understanding of the fluids displacement mechanism on the pore-scale that can only be addressed through laboratory experiments. In this study, we investigate why sequential N2-CO2 HnP recovers more oil than pure CO2 HnP. We found that N2 and CO2 perform similarly in the displacement of free fluids (FF), but N2 displaces little capillary bound fluids (CAF). However, replacing N2 with CO2 after a few N2 HnP cycles results in significant improvement in the recovery of CAF in the medium-sized pores than the HnP using CO2 exclusively. The injected N2 displaces pore fluids directly by squeezing their volumes but can only work on highly mobile FF. The displacement of fluids by CO2 relies more on creating a fluids/CO2 mixture and the subsequent swelling effect that can also displace CAF. Nevertheless, the N2 does not just ‘push’ the fluids out but also enhanced the rock’s hydraulic conductivity by possibly enlarging the pores and thus resulted in higher CAF recovery in the later cycles of HnP using CO2. More optimized N2-CO2 HnP procedures may further boost the recovery of fluids in the medium-sized pores, where a significant amount of hydrocarbon would remain unrecovered.

APPLICATION OF DISPLACEMENT CHARACTERISTICS FOR FORECASTED PRODUCTION INDICATORS EXPRESS-EVALUATION

Background Recently, in the oil and gas production complex, there has been a steady trend towards a deterioration in the structure of oil and gas reserves, which, in turn, imposes special conditions and requirements when performing predictive calculations of production levels. This is especially true for deposits with carbonate reservoirs of a complex type with high heterogeneity, in particular fractured-pore cavernous limestones and dolomites. Let’s consider carbonate reservoirs of field N as an example. According to the current project document, the field provides for the formation of a system for the development of facilities with waterflooding of reservoirs and the use of water and water-gas mixture as their working agents. The efficiency of the process of oil displacement by a working agent according to field data is expressed by the so-called oil displacement characteristics by water, which are the dependences of oil recovery on the volume of water that has penetrated into the reservoir. The displacement characteristic for an oil deposit more fully characterizes the efficiency of the development of an oil deposit than, for example, the oil recovery coefficient. The displacement characteristic reflects the history of the reservoir, clearly showing the effectiveness of the displacement process at any time of development, and is a convenient form for studying the nature and characteristics of the development and flooding of an oil reservoir. The displacement characteristic describes not only the final oil recovery in the reservoir, but also the dynamics of the oil recovery intensity coefficient from the water cut of the product during the development of heterogeneous formations in the mode of oil displacement by water. Aims and Objectives Obtaining an analytical displacement characteristic that takes into account the experience of developing analogous deposits and actual operating data, as well as further adaptation to the displacement characteristic obtained from the results of hydrodynamic modeling, in which all the involved displacement mechanisms are most fully represented. Results The performed analysis of the features of the geological structure of the field, analogous fields and the results of hydrodynamic modeling made it possible to construct a displacement characteristic that takes into account all the geological features of the field and the introduction of water and gas effects. The obtained displacement characteristic allows you to quickly perform calculations of predicted production indicators without the use of lengthy calculations on hydrodynamic models.

Computational study on mechanisms and kinetics of the atmospheric CFCl2CH2O2 with Cl reaction

Ab initio BMC-CCSD//B3LYP calculations of the potential energy surfaces (PESs) are associated with the rate constants and branch ratio of products by means of RRKM theories to research the mechanism and product distribution of the CFCl2CH2O2 with Cl reaction. The singlet and triplet PESs of this reaction have been calculated. Addition/elimination and SN2 displacement mechanisms are located on the singlet PES, and SN2 displacement and H-abstraction are located on the triplet PES. P1 (CFCl2CHO + HClO) are expected to the primary products at T ≤ 2400 K, which is by original barrierless Cl addition to the terminal-O atom in CFCl2CH2O2 and then eliminate HClO molecule, and the branch ratio of products rely on collision energy. The H-abstraction products on the triplet PES are the dominant products at higher temperatures. At 298 and 500 K, the total rate constants are not subject to pressure, conversely, the total rate constants presented typical falloff behavior at 1000 and 3000 K. The atmospheric lifetime of CFCl2CH2O2 in Cl is around one day. TD-DFT computations imply that IM1 (CFCl2CH2OOCl) and IM2 (CFCl2CH2OClO) will photolyze under the sunlight.

Construction of an efficient development mode for buried-hill fractured reservoirs in Bohai Bay

Fractured reservoirs are very complicated due to the coexistence of matrix and fractures. In addition, there are plenty of micro-fractures and a few dissolution pores rather than the traditional pores in the matrix of buried-hill fractured reservoirs. Thus, the performance of water flooding is mainly decided by the storage, percolation, and oil displacement characteristics of both fracture and matrix. However, the distribution and transmissibility of both macro-fractures and micro-fractures are actually heterogeneous due to the special origins. Moreover, the mass transfer between matrix and fracture is complicated. Therefore, it is very difficult to construct an effective development mode to obtain a favorable development effect. With the objective of effectively developing such reservoirs, JZ25- 1S in Bohai Bay in China was taken as an example in this paper. First, experiments were conducted to study the stress sensitivity of both matrix and fractures in buried-hill fractured reservoir, and simulations were performed to optimize the initial development project of depletion. Then, 3D large-scale experiments and simulations were demonstrated to study the oil displacement mechanisms and contributions of matrix and fracture for choosing optimal water flooding mode. Subsequently, the impacts of well pattern, injection-production ratio, and water flooding modes on development effects were studied by experiments and production practices in water flooding stage. Ultimately, an effective development mode was presented and used in the JZ25-1S reservoir. Cited as : Ge, L., Tong, K., Meng, Z., Zhu, Z., Zhu, X. Construction of an efficient development mode for buried-hill fractured reservoirs in Bohai Bay. Advances in Geo-Energy Research, 2020, 4(2): 162-172, doi: 10.26804/ager.2020.02.05

Nanoparticle-stabilized microemulsions for enhanced oil recovery from heterogeneous rocks

Surfactant-stabilized microemulsions (MEs) are often used to reduce the capillary forces responsible for trapping residual oil inside rocks. Recent studies showed that the presence of nanoparticles (NPs) in ME could enhance oil recovery, however their interfacial interactions and the impact of rock characteristics is still unclear. The objective of this study was to understand the effect of microemulsions stabilized by nanoparticles (MENP) on pore-scale fluid displacement mechanisms in a heterogeneous rock such as Arkose. A novel method was developed to synthesize silicon oxide in-situ in a ME. These nanoparticles had less tendency to agglomerate compared to nanopowders and promoted the formation of Pickering emulsions. The impact of ME and MENP on oil displacement in Arkose was examined using microtomography integrated with miniature core flooding. Aged cores were subjected to flooding with different aqueous solutions to investigate the effectiveness of ME and MENP in enhancing oil recovery. We found that ME promoted oil mobilization by reducing IFT and enhancing emulsification. The ability of ME to solubilize adsorbed oil layers contributed to a wettability alteration from oil-wet to weakly water-wet. Therefore, ME could remove 20.0% of additional oil after waterflooding. The incremental oil removal with MENP compared to waterflooding (34.3%) was higher than that of ME due to the emulsification of oil into even smaller droplets where NPs and surfactants synergistically interacted at the interface. The small oil droplets could penetrate small capillary elements of the rock that were inaccessible to ME, leading to stronger wettability alteration especially in carbonate cement.

Non-Linear Displacement Mechanisms of Thermally Actuated MEMS Chevron

Non-linearity in actuation of MEMS devices are essential in many applications. Previously, we presented the design and modeling of a NanoThermoMechanical AND logic gate, which is one of the building blocks of thermal computing (i.e., data processing based on heat instead of electricity). The gate is achieved through the coupling between near-field thermal radiation and MEMS thermal actuation. In the process, we developed two novel non-linear displacement mechanism of thermally actuated microstructure silicon V-shaped chevron beams which were required to achieve the desired thermal AND gate operation. In this work, we introduce the design, fabrication, and characterization of the two non-linear mechanisms using novel and ingenious chevron mechanisms consisting of spring-assisted reduction and cascading chevrons amplification for the reducing and the amplification mechanisms, respectively. The results show non-linearity can be achieved successfully through demonstrated and easy-to-manufacture chevron mechanisms. [2019-0233]

Dynamics of emulsion generation and stability during heavy oil displacement with chemicals and nanoparticles: Qualitative analysis using visual 2D data

There are a plethora of factors that may impact the viscous finger profiles observed in heavy oil-in-water emulsification in porous media such as chemical properties, chemical reaction, capillary number, mobility ratio, interfacial tension (IFT) gradient, chemical concentration, wettability, pH, and brine properties. To investigate such impact, we studied a large series of in-situ heavy oil-in-water emulsifications at various conditions using emulsifiers such as anionic surfactants, cationic surfactants, and NaOH (sodium hydroxide). For the stabilization of the emulsions formed with the emulsifiers, we tested nanofluids (silica, cellulose nanocrystal, zirconia, alumina) and polymers. 2-D visual results displayed that there exist finger profiles which strongly correlate with stable Winsor type 4 heavy oil-in-water emulsion generation along with “semi-stable” Winsor type 4 heavy oil-in-water emulsification. By controlling the structure of emulsion droplets and correlating observed multiple finger interactions to the materials, we enable the selection of novel designs for effective heavy-oil recovery as well as corresponding displacement mechanisms.

Theoretical investigations on •Cl-initiated atmospheric degradation of CHX2O2 (X = F, Cl)

The triplet and complex singlet potential energy surfaces (PES) of the Cl + CHX2O2 (X=F, Cl) reactions have been investigated at the BMC−CCSD//B3LYP/6-311++G(d,p) level. Addition/elimination and SN2 displacement mechanisms are revealed on the singlet PES. H-abstraction and SN2 displacement mechanisms are located on the triplet PES. Rice-Ramsperger-Kassel-Marcus (RRKM) theory and transition-state theory (TST) are employed to calculate the overall and individual rate constants over a wide range of temperatures and pressures. It is predicted that IM1X (CHX2OOCl (X=F, Cl)) formed by collisional stabilization is dominated at T≤800 K and T≤400 K, respectively; P1X (CX2O(X=F, Cl) + HClO) was the major products at 800–2800 K and 400–3000 K, respectively; and the channel of production P3F (CF2O2 + HCl) dominant the reaction at T ≥ 2800 K. The lifetimes of CHX2O2 (X=F, Cl) in the presence of Cl are predicted to around 1.17 and 2.98 weeks, respectively. Moreover, time-dependent density functional theory (TDDFT) calculations suggest that IM1X (CHX2OOCl (X=F, Cl)) will photolyze under the sunlight.

An investigation on phase behaviors and displacement mechanisms of gas injection in gas condensate reservoir

Cyclic gas injection into gas condensate reservoir is regarded as an effective development method to enhance condensate oil recovery. The aim of this work is to investigate the phase behavior and displacement mechanism of gas injection in gas condensate reservoir. Based on the equation of state and the phase equilibrium theory, the phase behavior of condensate oil in the formation mixed with various gas (CO2, N2, CH4, C2H6 and re-injected gas) has been analyzed. By calculating the Minimum Miscible Pressure (MMP), the miscibility of various gas was discussed and the effect of intermediate component in the re-injected gas on miscibility was evaluated. Moreover, a series of numerical simulations modeling the five-spot well network were conducted to investigate the displacement mechanism of gas injection using a compositional simulator. The results show that the injection of N2, CH4 and re-injected gas can raise the bubble point pressure of condensate oil and is conductive to the re-evaporation of condensate oil; whereas, injecting C2H6 or CO2 have little effect on it. The miscibility of re-injected gas increases with the intermediate component fraction. It is observed that at the reservoir pressure of 130 bar and reservoir temperature of 366.5 K, N2 and CH4 can evaporate the condensate oil in the formation by the function of gas extraction, with no miscibility; nevertheless, CO2 and C2H6 can be miscible with condensate oil to enhance the condensate recovery. For the cyclic gas injection, the higher the mole fraction of intermediate component, the more likely the miscibility occurs.

Static and dynamic evaluation of the effect of nanomaterials on the performance of a novel synthesized PPG for water shut-off and improved oil recovery in fractured reservoirs

Among different methods which are introduced to reduce unwanted water production, “Preformed Particle Gel” (PPG) is a recently developed type of these gels that can have important advantages such as temperature resistance and long-term stability. The aim of the present work is to synthesize a new type of PPG in which the above specifications are improved even further with the advantage of the Nano-material (here after called N-PPG) and then investigate its effectiveness via static bulk tests as well as dynamic Hele-Shaw and Micromodel tests. In static tube tests, the swelling performance of N-PPG samples was evaluated under different conditions. The examined parameters include various pH of the environment, the type and concentration of ions in the brine, temperature, particle size, and presence of carbon dioxide. Static results proved the temperature stability, pH-insensitivity, and long-term stability of the synthesized N-PPG. The PPG with the most suitable specification in the bulk tests was selected for further performance analysis in dynamic tests through Hele-Shaw cell and micromodel setups. The effectiveness and performance of the N-PPG on increasing the sweep efficiency of water injection and improving the oil production in Low Salinity Water flooding (LSWF) was studied for fractured systems. Dynamic Hele-Shaw cell tests showed that residual resistance factor (the factor which defines the gel ability to control water fingering) decreased with the increment of the brine concentration and the injection rate above a certain limit. In addition the size of dry particles shall be optimized for the best outcome of the treatment. The experimental results in the presence of CO2 showed superior sealing and dehydration performance of the present N-PPG compared to the PPG samples reported in the open literature. Eventually, visual micromodel tests revealed the involved microscale displacement mechanisms and confirmed the effectiveness of the swollen gel particles for reducing the effective permeability of the wide fractures and diverting the flow of the water to the matrix and as a result improving the sweep efficiency without intruding to the matrix and causing any formation damage or skin.

Salter-Harris type II fractures of the distal tibia: Residual postreduction displacement and outcomes-a STROBE compliant study.

We assessed factors associated with premature physeal closure (PPC) and outcomes after closed reduction of Salter-Harris type II (SH-II) fractures of the distal tibia. We reviewed patients with SH-II fractures of the distal tibia treated at our center from 2010 to 2015 with closed reduction and a non-weightbearing long-leg cast. Patients were categorized by immediate postreduction displacement: minimal, <2 mm; moderate, 2 to 4 mm; or severe, >4 mm. Demographic data, radiographic data, and Lower Extremity Functional Scale (LEFS) scores were recorded.Fifty-nine patients (27 girls, 31 right ankles, 26 concomitant fibula fractures) were included, with a mean (±SD) age at injury of 12.0 ± 2.2 years. Mean maximum fracture displacements were 6.6 ± 6.5 mm initially, 2.7 ± 2.0 mm postreduction, and 0.4 ± 0.7 mm at final follow-up. After reduction, displacement was minimal in 23 patients, moderate in 21, and severe in 15. Fourteen patients developed PPC, with no significant differences between postreduction displacement groups. Patients with high-grade injury mechanisms and/or initial displacement ≥4 mm had 12-fold and 14-fold greater odds, respectively, of PPC. Eighteen patients responded to the LEFS survey (mean 4.0 ± 2.1 years after injury). LEFS scores did not differ significantly between postreduction displacement groups (P = .61).The PPC rate in this series of SH-II distal tibia fractures was 24% and did not differ by postreduction displacement. Initial fracture displacement and high-grade mechanisms of injury were associated with PPC. LEFS scores did not differ significantly by postreduction displacement.Level of Evidence: Level IV, case series

Seismic response of partially saturated soils beneath shallow foundations under sequential ground motions

Induced partial saturation is an innovative soil improvement technique intended to mitigate earthquake-induced liquefaction. Historical records indicate that successive earthquakes may occur in high seismic areas. Therefore, a comprehensive understanding of the response of partially saturated soils to sequential ground motions is of great significance for the rational design and execution of this method in engineering practice. In this study, a series of dynamic centrifuge experiments were conducted to investigate the impacts of sequential ground motions on the behavior of partially saturated soils beneath shallow foundations. Two different shallow foundation models with a bearing pressure of 135 kPa and 50 kPa were examined. Three seismic simulations, in order of increasing amplitudes, were sequentially applied to loosely-packed partially saturated sand models prepared with air injection technique. The assessment of the test results indicated that shallow foundations resting on saturated models of loose sand did suffer excessive settlements with each event, producing a large embedment of the foundation. However, much smaller settlements were recorded for partially saturated ground, and the level of the foundation embedment remained limited in this case. The deformation vector fields also indicated that different displacement mechanisms were observed for each successive event.

Experimental study on the enhanced oil recovery by in situ foam formulation

AbstractIn situ CO2foams (ISCF) are studied systematically by combining in situ CO2gas reactants (carbonate anhydrous, hydrochloric acid) and bio‐based surfactant. Sandpack flooding experiments at 60°C along with PVT experiments were carried out to analyze the oil displacement mechanisms. The results showed that ISCF could increase oil recovery from heterogeneous multilayer formation of permeability ratio over 6, and displacement efficiency increased with the injection volume increased before the injection of 1 PV. The incremental oil recovery by ISCF was much greater than that of conventional foam or in situ CO2(ISC) without foam under the same injection conditions. The generated CO2foam could reduce the interfacial tension between displacement phase and displaced phase effectively which contributed to the great increase in capillary number. The CO2dissolution greatly reduced the viscosity of crude oil, and the highest viscosity reduction rate at 60°C could be as high as 98%. The Ca2+concentration of produced liquids analysis revealed the ISCF could distribute intelligently the acid in heterogeneous formations.

A relative permeability model for CBM reservoir

Relative permeability is an effective tool for studying multiphase fluid flow in porous media. For conventional reservoirs, a relatively reliable relative permeability curve can be obtained by laboratory core test. But because of the coalbed gas reservoir permeability is low, the stable steady state method will take a very long time, and the operation is relatively complex. For the non-steady state method, the coalbed gas reservoirs are rich in micro nano pore, which causes the strong heterogeneity and gas is easy to break in through the cracks, it makes non-steady displacement experiment very difficult. Also, the experimental results are greatly affected by human factors and computational methods. Therefore, based on the ideal pore structure and the consideration of different displacement mechanisms, the analytical method not only helps to understand the mechanism of gas water two-phase flow, but also is a convenient and practical method. Coalbed methane reservoirs are rich of nano pores, and the percolation process is more complicated due to the water. Consider of the nano pore of the coal, the capillary force’s effect will be more important. The different pressure will cause different flow channel, which will change the permeability. In this paper, the relative permeability model of coalbed methane reservoir has been built which considers the gas diffusion and slippage effect, pore throat structure parameter, water saturation distribution, and gas water interface pressure drop. It can describe the difference flow channel between different pressure.

Permeability alteration by salt precipitation: numerical and experimental investigation using X-Ray Radiography

The injection of a gas phase through a water saturated porous medium can reduce the water saturation not only by displacement mechanisms but also by evaporation mechanisms. In the presence of brine, this process can induce salt crystallization and precipitation within the porous medium with a risk of permeability alteration. In the field of gas production and storage, the occurrence of such a phenomenon can have detrimental consequence on the well productivity or injectivity. In this work, we investigated experimentally and numerically the effect of dry gas injection on salt precipitation and permeability impairment. State of the art equipment designed for high throughput coreflood experimentation was used to capture the dynamic of salt migration using X-Ray radiography. A set of experiments have been conducted on a sample of Bentheimer sandstone (10mm in diameter and 20 mm in length) as well as a two layers composite sample with a significant permeability contrast. Experiments were conducted using Nitrogen and KBr brine with different boundary conditions (i.e. with and without capillary contact). Results showed that salt precipitation results from the interplay of different parameters, namely pressure gradient, brine salinity, capillary forces and vapor partial pressure. Experimental observations indicate that in the case of dry gas injection, salt systematically precipitates but permeability alteration is observed only if a capillary contact is maintained with the brine. We built a 2D flow model integrating two-phase Darcy flow, capillary forces, salt effect on vapor partial pressure, dissolved salt transport, as well as the different PVT equilibria needed to describe properly the systems. Once calibrated, the model showed good predictability of lab scale experiment and thus can be used for parametrical study and upscaled to the well bore scale.

Pore-scale dynamics of nanofluid-enhanced NAPL displacement in carbonate rock

This study presents a pore-scale investigation of two-phase flow dynamics during nanofluid flooding in subsurface formations containing non-aqueous phase liquids (NAPLs) such as crude oils. The goal was to gain fundamental understanding of the dominant displacement mechanisms of NAPL at different stages of nanofluid injection in a carbonate rock using x-ray microtomography integrated with a miniature core-flooding system. The nanofluid consisted of surfactant-based microemulsions with in-situ synthesized silica nanoparticles. After establishing its initial wettability state, the carbonate core sample was subjected to various pore volumes (PV) of nanofluid flooding (from 0.5 to 10) to examine the impact on NAPL flow dynamics. We found that most NAPL mobilization occurred within the first PV of injection, removing nearly 50% of NAPL from the rock. The nanofluid invaded into larger pores first due to a sharp decrease in NAPL/brine interfacial tension (from 14 to 0.5 mN/m) and contact angle (from 140 to 88°). With higher amount of nanofluid delivered into the pores through advection, over 90% of NAPL droplets were emulsified and their size decreased from 9 to 3 μm. Subsequent nanofluid injection could further remove NAPL from the smaller pores by altering the thickness of NAPL layers adsorbed on the rock. This dynamic solubilization process reached equilibrium after 5 PV of injection, leading to a reduced layer thickness (from 12 to 0.2 μm), a narrower in-situ contact angle distribution around 81°, and an additional 16% of NAPL removal.

Simulation of space charge transport in solid dielectric materials using transmission lines modeling method

In this paper, a lumped RC circuit model, which is based on the Transmission Line Modeling (TLM) method, is used to describe the space charge production and displacement mechanisms in three different solid dielectric materials (LDPE, PTFE and FR4). Each dielectric material is considered as a transmission line with the capacitive and resistance elements. The obtained circuit equations are solved along with the continuity equations for the various charged species in the bulk of solid dielectric material. The electric potential and field, density of different charged species and their recombination rates, resistive and capacitive properties of the solid dielectric material are calculated. In addition, the effects of the variations in the applied voltage, dielectric permittivity and temperature on these physical parameters are examined. Besides, compared with LDPE and PTFE, the net charge density increment rate in FR4 is much higher. Moreover, the influences of temperature on the net charge density in LDPE are not significant. Furthermore, at the higher applied voltages, the current density is increased. Interestingly, the effects of temperature variations on the recombination rates, net charge and current density in LDPE are much lower. Hence, the suitability of LDPE as solid dielectric material is proved.

Experimental investigation on transport property and emulsification mechanism of polymeric surfactants in porous media

Polymeric surfactants display different capabilities in migration rules and emulsifying crude oil as compared with that of traditional polymers attributing to the co-existence of hydrophilic and hydrophobic groups in molecular chains. To investigate the migration rules of polymeric surfactants in porous media and the matching relationship between polymeric surfactants and porous media, seepage-behavior experiments of different concentrations of polymeric surfactants in different permeability and different length cores were first carried out. The generation of emulsified oil droplets with the polymeric surfactants was then elucidated by comparing core flooding experiments with different injection rates, different saturated oil types and different polymeric surfactants concentrations. The flow characteristics of the emulsion and displacement mechanisms were evaluated by microscopic displacement experiments. The results showed that unlike polymers, when the polymeric surfactant was transported in porous medium, the pressure was difficult to reach a stable state. Based on the matching coefficient, the migration rules of polymeric surfactants in porous media could be defined as high blocking weak flow mode (λ < 14.7), a blocking flow equalization mode (14.7<λ < 19.7) and a smooth flow mode (λ > 19.7). The main reasons for the formation of polymeric surfactants emulsions are a certain shearing action, the snapping action of hydrophobic microdomains on residual oil droplets and assisted effect of colloidal asphaltene. Capillary number(Nc) was used as an evaluation index to divide the emulsification action into four zones: non-emulsified zone(Nc < 2.18 × 10−5), high-efficiency emulsification zone (2.18 × 10−5<Nc < 8.7 × 10−5), optimal-emulsification zone (8.7 × 10−5<Nc < 1.46 × 10−4) and emulsified excess zone(Nc > 1.46 × 10−4). The emulsion microscopic flooding experiment showed that in the porous medium, the transport characteristics of polymeric surfactants emulsion were mainly plugging action of single large emulsion particle, stacking and plugging action of small emulsion particles, forming “emulsion bridge” to block super large pores and vortex action of different sizes emulsion particles.

New Barium Vanadate BaxV2O5 (x ≈ 0.16) for Fast Lithium Intercalation: Lower Symmetry for Higher Flexibility and Electrochemical Durability

AbstractNa0.33V2O5‐type metal vanadates generally show better cycling stability than α‐V2O5 as a cathode in Li‐ion batteries, because they contain enough crystallographic voids that allow for lithium intercalation without significant structural deformation, but metal leaching upon cycling deteriorates their capacity retention. Here a new barium vanadate Ba0.16(1)V2O5 is reported that does not undergo Ba leaching during cycling and shows a great promise for fast Li intercalation. Sr0.15(1)V2O5 is isostructural to Na0.33V2O5 (space group C2/m), while Ba0.16(1)V2O5 adopts a new structure (space group P21/c), a derivative of Na0.33V2O5. The framework of Ba0.16(1)V2O5 consists of edge‐shared VO6 octahedral layers and the VO5 pyramidal bridge, generating unidirectional tunnels. Unlike the in‐plane arrangement of atoms in Sr0.15(1)V2O5, the nonplanar arrangement in Ba0.16(1)V2O5 makes the host framework more flexible and creates larger voids for Ba. Compared with the combination of displacement and intercalation mechanisms in the Sr0.15(1)V2O5 cathode, Li intercalation looks dominant in the Ba0.16(1)V2O5 cathode due to its increased flexibility. Hence, Ba0.16(1)V2O5 exhibits improved cycling stability compared to Sr0.15(1)V2O5, suggesting that lower symmetry leads to higher cyclic stability in the V2O5‐related compounds. This study illustrates how guest cations can tune the structural symmetry to modulate the reaction mechanism of electrode materials toward superior performances.