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Low primary recovery factor and rapid production decline necessitates the proposal of enhanced oil recovery methods to mobilize the remaining oil resource of tight reservoirs, especially for oil-wet ones, and wettability alteration by injecting a chemical agent such as a surfactant is a promising option. A discrete-fracture-network-based mathematical model is developed with consideration of the displacement mechanisms and complicated physical-chemical phenomena during EOR by wettability alteration, and this model numerically solved by the fully implicit method. Simulation cases are conducted to investigate the production performance and key factors of cyclic injection of a surfactant. Cyclic injection can significantly improve the production of oil-wet tight reservoirs, and the ultimate recovery factor can be increased by 10 percent. The reason is that a surfactant can alter the wettability of a reservoir from oil wet to medium or even water wet, which triggers spontaneous imbibition and favors oil movement from a matrix into a fracture. Better EOR results can be achieved with decreasing oil viscosity, increasing matrix permeability, or decreasing fracture spacing. Cyclic surfactant injection is applicable to reservoirs with an oil viscosity of less than 7 mPa·s, a matrix permeability bigger than 0.01 mD, or a fracture spacing smaller than 150 m. It is favorable for the wettability alteration method by maintaining capillary pressure and reducing residual oil saturation as much as possible.

Water injectors and polymer injectors coexist after well pattern infilling in some offshore oilfields, which exerts a deep impact on oil exploitation. In order to quantitatively characterize the injected water-polymer perturbation degree and analyze perturbation laws, water-polymer perturbation coefficient is proposed and established by comparing the displacement process of water-polymer coflooding and pure polymer flooding, which quantifies the dynamic change of displacement volume of injected water and polymer, and controlling strategy is discussed correspondingly to improve the development effect of water-polymer coflooding. Finally, a field case is used to demonstrate this new evaluation method. The results show that water-polymer perturbation coefficient has a good correlation with oil increasing, and water-polymer coflooding process can be divided into five stages according polymer perturbation coefficient. In addition, water-polymer coflooding has a better oil increasing effect than pure polymer flooding at the initial stage, but for a long period, development effect of pure polymer flooding is much better. The result has a great significance to quantitatively characterize water-polymer perturbation degree and make adjustment measurements.

Mutations in Valosin-containing protein (VCP) have been implicated in the pathology linked to inclusion body myopathy, paget disease of bone and frontotemporal dementia (IBMPFD). VCP is an essential component of AAA-ATPase superfamily involved in various cellular functions. Advanced In-silico analysis was performed using prediction based servers to determine the most deleterious mutation. Molecular dynamics simulation was used to study the protein dynamics at atomic level. Molecular docking was used to study the effect of mutation on ATP/ADP transition in the kinase domain. This ATPase of 806 amino acids has four domains: N-terminal domain, C-terminal domain and two ATPase domains D1 and D2 and each of these domains have a distinct role in its functioning. The mutations in VCP protein are distributed among regions known as hotspots, one such hotspot is codon 155. Three missense mutations reported in this hotspot are R155C, R155H and R155P. Potentiality of the deleteriousness calculated using server based prediction models reveal R155C mutation to be the most deleterious. The atomic insight into the effect of mutation by molecular dynamics simulation revealed major conformational changes in R155C variants ATP binding site in D1 domain. The nucleotide-binding mode at the catalytic pocket of VCP and its three variants at codon 155 showed change in the structure, which affects the ATP–ADP transition kinetics in all the three variants.

The sluggish kinetics and large volume expansion arising from the large ionic radius of Na+ remain elusive weaknesses of sodium ion batteries (SIBs). Here, we report a transition from bulk diffusion to surface-dominant pseudocapacitive charge storage by nanoscaling and heterostructuring, which enables fast and stable charge storage kinetics for SIBs. An electronic attraction induced self-assembly strategy was developed for the synthesis of the 1T/2H MoS2@SnO2 heterostructure. Ultrasmall SnO2 nanoparticles with a low crystallinity were uniformly distributed on the basal plane of MoS2. The intercalated SnO2 serves as an interfacial pillar to restrict the restacking of MoS2 nanosheets, whereas dual-phase 1T/2H MoS2 provides a continuous network for efficient charge transfer and restrains the aggregation of NaxSn. As a result, the 1T/2H MoS2@SnO2 heterostructure exhibits a higher specific capacity (626 mA h g−1 at 0.1 A g−1), and superior cycling and rate capabilities (262 mA h g−1 at 2 A g−1 for 500 cycles) compared to the raw MoS2 and 2H MoS2@SnO2 counterparts. Electrochemical kinetics analyses reveal that the charge transfer kinetics are boosted by the synergistic effect between the 1T/2H MoS2 and SnO2 nanoparticles. Quantitative examination into the origin demonstrated that the Na+ storage is dominated by the fast surface redox reaction, which endows the heterostructure with a durable high rate capability.

Four MoO3 samples with the Zn element doped mole ratio of 0%, 3%, 6% and 9% were prepared by applying a convenient one-step hydrothermal synthesis method, and the samples presented three-dimensional microflower-like structures assembled by nanosheets. The systematic analysis results indicate that the 6 mol% Zn-doped sample had the most amazing detection characteristics for 50 ppm CO, with a response of 31.23 (4 times of the pure MoO3) at a lower temperature (240 °C). The large specific surface area, big pore size and tiny particle size were proved to be beneficial to the gas sensitivity, which promotes gases transfer and provides more gases landing points during the gas-sensitive reaction. Besides, based on the density functional theory (DFT), the facilitation effect of doped Zn on the adsorption ability of MoO3 to CO molecule was verified from the perspective of electronic properties. The excellent gas-sensing performances indicate that the 6 mol% Zn-doped MoO3 has potential to be applied as a reliable CO sensor.

The detection of oil-dissolved gases (such as CO, CH4 and H2) in transformers on-line is an important technology to predict and judge the operating status of transformers. Microstructure and gas sensing performance of Au-MoS2 microspheres synthesized by hydrothermal method were investigated in the present research. The results indicated Au-MoS2 based gas sensor has excellent response to CO, CH4 and H2 gases with maximum responses of 25.48, 16.75 and 8.48 at 30 ppm in their optimum working temperature (150 °C, 150 °C, 175 °C). In addition, First-principle calculation was carried out to expound the sensing mechanism in detail. The conclusions of this study suggest that Au-MoS2 monolayer exhibits a promising applicable future in sensor detecting of oil-dissolved gases in power transformer.

Novel nanoscale lanthanide and mixed lanthanide metal-organic frameworks with thermo-sensitive polymer as organic links were successfully prepared. They were obtained through biomimetic mineralization approach. This is the first report of fabrication of polymer-metal-organic frameworks via biomimetic mineralization. The particle size was in the range from 200 to 500 nm. The photoluminescent properties of the materials have also been studied. The fluorescence intensity changed in different solvent (N, N-dimethylformamide, tetrahydrofuran, ethanol, acetone, dichloromethane, water), so solvent recognition can be achieved by using the polymer-metal-organic frameworks. The materials are also very sensitive to water (even trace water) in the mixed solutions composed of water and organic solvents. Especially the mixed lanthanide polymer-metal-organic frameworks can be designed to a ratiometric fluorescent nanosensor. The novel fluorescence detection materials have very important potential applications in the field of chemical industry.

In this work, we reported the successful synthesis of a novel two-dimensional porous NiO nanosheet via a one-step hydrothermal route and subsequent calcination. It was surprise found that such NiO nanosheet exhibits a superior gas response towards H2. The enhanced sensing ability may be benefited from the porous nanostructure, resulting in more sufficient pathways for gas diffusion and larger surface for chemical reaction. We hoped our findings could be in favor of further investigations on the fabrication of perfect two dimensional architectures.

In this paper, we reported the morphology controllable synthesis of hierarchical WO3 nanostructures , i.e. nanorods , nanospheres and nanoflowers, via a facile hydrothermal route. All the obtained WO 3 nanostructures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET), respectively. A possible growth mechanism for the three various nanomaterials was proposed in detail. WO 3 based gas sensors were fabricated with the synthesized nanomaterials and the gas sensing performances to acetylene (C2H2 ), one of the fault characteristic gases dissolved in power transformer oil, were systematically measured. It was found that the sensor based on nanosheet-assembled nanoflowers with largest surface (56.74 m 2g−1) exhibits the highest sensing performance including gas response (32.31) and response-recovery time (12 s, 17 s) to 200 ppm C2H2. The results indicate that WO3 sensing materials could be a promising choice for synthesizing high-performance C2H2 sensors for the judgement of the early latent faults of the oil immersed transformer.

For the first time, HY-2A/GM-derived gravity anomalies determined with the least-squares collocation method and ship-borne bathymetry released from the National Centers for Environmental Information (NCEI) are used to predict bathymetry with the gravity-geologic method (GGM) over three test areas located in the South China Sea (105–122°E, 2–26°N). The iterative method is used to determine density contrasts (1.4, 1.5, and 1.6 g/cm3) between seawater and ocean bottom topography, improving the accuracy of GGM bathymetry. The results show that GGM bathymetry is the closest to ship-borne bathymetry at check points, followed by SRTM15+V2.0 model and GEBCO 2020 model. It is found that in a certain range, the relative accuracy of GGM bathymetry tends to improve with the increase of depth. Different geological structures affect the accuracy of GGM bathymetry. In addition, the influences of gravity anomalies and data processing method on GGM bathymetry are analyzed. Our assessment result suggests that GGM can be widely applied to bathymetry prediction and that HY-2A/GM-derived gravity data are feasible with good results in calculating ocean depth.

Injection conformance reversion commonly observed during polymer flooding in offshore heterogeneous heavy-oil reservoirs weakens the volumetric sweep of polymer solution and compromises its EOR results. To investigate its mechanisms and impact factors, one mathematical model to predicate injection conformance behavior is constructed for heterogeneous reservoirs based on the Buckley-Leverett function. The different suction capability of each layer to polymer solution results in distinct change law of the flow resistance force, which in turn reacts upon the suction capability and creates dynamic redistribution of injection between layers. Conformance reversion takes place when the variation ratio of flow resistance force of different layers tends to be the same. The peak value and scope of conformance reversion decrease and reversion timing is advanced as oil viscosity or permeability contrast increases, or polymer concentration or relative thickness of low permeable layer decreases, which compromises the ability of polymer flooding to improve the volumetric sweep and lower suction of the low permeable layer. The features of offshore polymer flooding tend to make the injection conformance V-type and create low-efficiency circulation of polymer in a high permeable layer more easily. These results can provide guidance to improve the production performance of polymer flooding in offshore heterogeneous heavy-oil reservoirs.

Oil-immersed power transformers are considered to be one of the most crucial and expensive devices used in power systems. Hence, high-performance gas sensors have been extensively explored and are widely used for detecting fault characteristic gases dissolved in transformer oil which can be used to evaluate the working state of transformers and thus ensure the reliable operation of power grids. Hitherto, as a typical n-type metal-oxide semiconductor, tungsten trioxide (WO3) has received considerable attention due to its unique structure. Also, the requirements for high quality gas detectors were given. Based on this, considerable efforts have been made to design and fabricate more prominent WO3 based sensors with higher responses and more outstanding properties. Lots of research has focused on the synthesis of WO3 nanomaterials with different effective and controllable strategies. Meanwhile, the various morphologies of currently synthesized nanostructures from 0-D to 3-D are discussed, along with their respective beneficial characteristics. Additionally, this paper focused on the gas sensing properties and mechanisms of the WO3 based sensors, especially for the detection of fault characteristic gases. In all, the detailed analysis has contributed some beneficial guidance to the exploration on the surface morphology and special hierarchical structure of WO3 for highly sensitive detection of fault characteristic gases in oil-immersed transformers.

Hollow structured nanofibers have attracted much attention in diverse domains owing to their unique physicochemical properties and characteristics. Gas sensing is one of the most promising applications. In electrical engineering, the detection of SF6 decomposing gas products is significant to monitor the insulation status online of gas insulated switchgear (GIS). This mini-review presents the developments of hollow structured nanofibers in synthesis strategies and gas sensing application, especially in the detection of SF6 decomposing gas products, including hydrogen disulfide (H2S), sulfur dioxide (SO2), thionyl fluoride (SOF2), and sulfuryl fluoride (SO2F2). In addition, the gas sensing mechanism of metal oxide hollow nanofibers based gas sensor are discussed.

In this study, highly sensitive Ag 2 O-doped ZnO nanorods based sensor was presented and developed to detect CH 4 gas, an extremely significant fault characteristic gas extracted from power transformer oil. Ag 2 O-doped ZnO nanorods sensing materials were synthesized with facile hydrothermal method, and characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. Side heated chemical gas sensor was fabricated and its sensing performances towards CH 4 were systematically investigated. The optimal operating temperature of the Ag 2 O-doped ZnO sensor was 280 °C for CH 4 sensing, and its gas sensing response to 10 ppm CH 4 was measured to be as high as 12.28. In addition, good linearity for low concentration of CH 4 gas was also obtained. The corresponding response-recovery time of the Ag 2 O-doped ZnO sensor was measured to be about 17-10s. All results provide reference and guidance for developing high-performance ZnO based gas sensors for CH 4 detection. All these excellent sensors performances indicate the large potential of the fabricated Ag 2 O decorated ZnO nanorods sensor for practical application of CH 4 detection.

We propose an efficient analytical upscaling method to compute the equivalent conductivity tensor for elliptic equations in three-dimensional space. Our approach uses perturbation expansion and Fourier analysis, and considers heterogeneity, anisotropy and geometry of coarse gridblocks. Through low-order approximation, the derived analytical solution accurately approximates the central-difference numerical solution with periodic boundary conditions. Numerical tests are performed to demonstrate the capability and efficiency of this analytical approach in upscaling fluid flow in heterogeneous formations. We test the method in synthetic examples and benchmark cases with both Gaussian random fields and channelized non-Gaussian fields. In addition, we examine the impact of each parameter on the upscaled conductivity, and investigate the sensitivity of the variance and correlation lengths to the coefficients. We also indicate how to extend this approach to multiphase flow problems.

Two novel hierarchical WO3/NiO microspheres with porous and rough surface have been prepared through a simple one-stop hydrothermal method. Interestingly, it is a surprise that the introduction of different amounts of WO3 plays a critical role in the growth and self-assembly of nanosheets and then the morphology of microsphere. Further gas sensing experiment demonstrates that the sensor based on porous microsphere possesses prominent performance towards 100 ppm ethanol at the optimal working temperature of 300 °C compared with that of rough microsphere. It is believed that the enhanced gas sensing properties benefit from the porous structure on the surface with abundant active sites and gas passages for sufficient gas adsorption and diffusion.

In this work, hierarchical WO3-NiO microflowers have been designed and prepared through a controllable hydrothermal route for high sensitivity detection of H2S produced by SF6 decomposition. The hierarchical flower-like nanostructures assembled with numerous nanosheets were influenced by the introduction of WO3, which is regarded as a significant strategy for improving the gas sensing properties. The synthesized nanostructures were tested by various characterization to investigate the different microstructures of the nanocomposites. The H2S sensing performances of the sensors fabricated with these flower-like nanostructures were measured, which indicated that 3.0 at% WO3-NiO microflower based sensor possessed excellent properties such as higher gas responses and more prominent repeatability compared with those of other fabricated sensors. The enhanced performances might be mainly ascribed to the creation of the heterojunction at n-type WO3 and p-type NiO interface, which caused the improvement of the potential barrier and depletion layer. In addition, the larger specific surface area of flower-like nanostructures also possessed abundant sites for surface reaction.

Hydrogen sulfide (H2S) is an important decomposition component of sulfur hexafluoride (SF6), which has been extensively used in gas-insulated switchgear (GIS) power equipment as insulating and arc-quenching medium. In this work, electrospun ZnO-SnO2 composite nanofibers as a promising sensing material for SF6 decomposition component H2S were proposed and prepared. The crystal structure and morphology of the electrospun ZnO-SnO2 samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The composition of the sensitive materials was analyzed by energy dispersive X-ray spectrometers (EDS) and X-ray photoelectron spectroscopy (XPS). Side heated sensors were fabricated with the electrospun ZnO-SnO2 nanofibers and the gas sensing behaviors to H2S gas were systematically investigated. The proposed ZnO–SnO2 composite nanofibers sensor showed lower optimal operating temperature, enhanced sensing response, quick response/recovery time and good long-term stability against H2S. The measured optimal operating temperature of the ZnO–SnO2 nanofibers sensor to 50 ppm H2S gas was about 250°C with a response of 66.23, which was 6 times larger than pure SnO2 nanofibers sensor. The detection limit of the fabricated ZnO–SnO2 nanofibers sensor toward H2S gas can be as low as 0.5 ppm. Finally, a plausible sensing mechanism for the proposed ZnO–SnO2 composite nanofibers sensor to H2S was also discussed.

Tin oxide SnO2-based gas sensors have been widely used for detecting typical fault characteristic gases extracted from power transformer oil, namely, H2, CO, CO2, CH4, C2H2, C2H4, and C2H6, due to the remarkable advantages of high sensitivity, fast response, long-term stability, and so on. Herein, we present an overview of the recent significant improvement in fabrication and application of high performance SnO2-based sensors for detecting these fault characteristic gases. Promising materials for the sensitive and selective detection of each kind of fault characteristic gas have been identified. Meanwhile, the corresponding sensing mechanisms of SnO2-based gas sensors of these fault characteristic gases are comprehensively discussed. In the final section of this review, the major challenges and promising developments in this domain are also given.

Polymer flooding, as the most effective chemical EOR technique, was widely and used in onshore oilfields in the world. Also, it has been successfully applied in China offshore oilfields as a major EOR technology. In general, compared with water flooding, the production rate in polymer flooding drops by less than 30% according to observations of onshore field application. However, the production rate dropped much more severely in mid to late stage of polymer flooding for plugging problems in W offshore oilfield, which is over 50% in some producers and leads to poor flooding performance and less incremental oil. In this study, we perform a systematic analysis through integrating production dynamic analysis, well testing and reservoir simulation for the mechanisms and impacts of the plugging during the polymer flooding based on actual field data. First, a typical 1-injector & 1 producer polymer flooding reservoir model was established. Through simulation with the detailed description of reservoir and polymer properties, the impacts of key parameters affecting the production rate of producers in different stages of polymer flooding were analyzed. In addition, the dynamic characteristics of well performance under the condition of different plugging location were examined. After that, the local grid radial refinement technology was utilized to calculate the plugging degree and pollution radius of the target wells. Finally, a full-field corner grid system numerical model with local grid radial refinement near the wellbore was built in W fileld. We performed history matching with target injectors and producers and determined the plugging degree of pollution radius near above wells. Through this field case study, the relationship between production rates and different stages of polymer flooding was identified. In addition, a diagnostic plot for characterizing the impact of plugging location on dynamic well performance was generated. Furthermore, the degree of plugging and pollution radius of all target wells was determined accurately. This study provides critical insights for understanding the polymer plugging mechanism and its effect on polymer flooding effectiveness in the offshore oil field. It also delivers a good reference for plugging removal design and optimization of polymer flooding strategy to maximize oil recovery.

Herein, we successfully prepared the Nickel oxide (NiO) nanomaterials with the structure of two-dimensional (2D) honeycomb-like nanoplates assembled by nanosheet arrays through the hydrothermal synthesis. In addition, the growth mechanism of this unusual nanostructure was proposed. Surprisingly, such NiO nanoplates exhibits superior gas-sensing properties to CO, which is mainly attributed to the hollow structure produced by the arrangement of nanosheets, contributing not only enough gases diffusion pathways but sufficient reaction sites during the gas sensing processes.