Ultra-low permeability reservoirs are characterized by small pore throats and poor physical properties, which areat the root of well-known problems related to injection and production. In this study, a gas injection f...Ultra-low permeability reservoirs are characterized by small pore throats and poor physical properties, which areat the root of well-known problems related to injection and production. In this study, a gas injection floodingapproach is analyzed in the framework of numerical simulations. In particular, the sequence and timing of fracturechanneling and the related impact on production are considered for horizontal wells with different fracturemorphologies. Useful data and information are provided about the regulation of gas channeling and possible strategiesto delay gas channeling and optimize the gas injection volume and fracture parameters. It is shown that inorder to mitigate gas channeling and ensure high production, fracture length on the sides can be controlled andlonger fractures can be created in the middle by which full gas flooding is obtained at the fracture location in themiddle of the horizontal well. A Differential Evolution (DE) algorithm is provided by which the gas injectionvolume and the fracture parameters of gas injection flooding can be optimized. It is shown that an improvedoil recovery factor as high as 6% can be obtained.展开更多
The glass-ceramics were prepared with the spodumene mineral as the main raw material,and the effects of ZrO_(2)replacing TiO_(2)on the samples were systematically investigated.The results show that the substitution of...The glass-ceramics were prepared with the spodumene mineral as the main raw material,and the effects of ZrO_(2)replacing TiO_(2)on the samples were systematically investigated.The results show that the substitution of ZrO_(2)for TiO_(2)is not conductive to precipitate𝛽β-quartz solid solution phase,but can improve the transparency and flexural strength of glass-ceramics.And the glass-ceramic with the highest visible light transmittance(87%)and flexural strength(231.80 MPa)exhibits an ultra-low thermal expansion of-0.028×10^(-7)K^(-1)in the region of 30-700℃.展开更多
Through the rapid carbonation test of SFRRC with different fiber volume fractions at ultralow temperature,the influence of ultra-low temperature damage on the carbonation resistance of SFRRC was analyzed,which provide...Through the rapid carbonation test of SFRRC with different fiber volume fractions at ultralow temperature,the influence of ultra-low temperature damage on the carbonation resistance of SFRRC was analyzed,which provides a theoretical basis for the application of SFRRC in ultra-low temperature engineering.The experimental results show that ultra-low temperatures can significantly weaken the carbonization resistance of SFRRC.When the temperature reaches 160℃,the carbonization depth increases by 67.66%compared with the normal state.The proper amount of steel fiber has an evident influence on the carbonation resistance of the material.However,when the addition amount exceeds the optimum content,the carbonation resistance of the material decreases.The grey prediction model established by constructing the original sequence can reasonably predict the carbonation resistance of SFRRC after ultra-low temperatures.展开更多
Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stac...Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.展开更多
Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order t...Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.展开更多
Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid st...Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.展开更多
Due to inherent limits of data acquisition and geophysical data resolution, there are large uncertainties in the characterization of subsurface fractures. However, outcrop analogies can provide qualitative and quantit...Due to inherent limits of data acquisition and geophysical data resolution, there are large uncertainties in the characterization of subsurface fractures. However, outcrop analogies can provide qualitative and quantitative information on a large number of fractures, based on which the accuracy of subsurface fracture characterization can be improved. Here we take the tectonic fracture modeling of an ultra-low permeability sandstone reservoir based on an outcrop analogy, a case study of the Chang6t~ Formation of the Upper Triassic Yanchang Group of the Wangyao Oilfield in the Ordos Basin of China. An outcrop at the edge of the basin is a suitable analog for the reservoir, but the prerequisite is that they must have equivalent previous stress fields, similar final structural characteristics, relative timing and an identical depositional environment and diagenesis. The relationship among fracture density, rock type and bed thickness based on the outcrop is one of the most important fracture distribution models, and can be used to interpret fracture density in individual wells quantitatively. Fracture orientation, dip, geometry and scale, also should be described and measured in the outcrop, and can be used together with structure restoration and single well fracture density interpretation to guide fracture intensity prediction on bed surfaces and to constrain the construction of the 3D fracture geometry model of the subsurface reservoir. The application of the above principles shows the outcrop-based tectonic fracture models of the target ultra-low permeability sandstone reservoir are consistent with fractures inferred from microseismic interpretation and tracer tests. This illustrated that the fracture modeling based on the outcrop analogy is reliable and can reduce the uncertainty in stochastic fracture modeling.展开更多
800 MPa grade new ultra-low carbon bainitic (NULCB) steel is the recently developed new generation steel. The microstructure in the coarse-grained heat affected zone (CGHAZ) of NULCB steel under laser welding cond...800 MPa grade new ultra-low carbon bainitic (NULCB) steel is the recently developed new generation steel. The microstructure in the coarse-grained heat affected zone (CGHAZ) of NULCB steel under laser welding conditions was investigated by thermal simulation. The influence of the cooling time from 800℃ to 500℃.t8/5 (0.3-30 s), on the microstructure of the CGHAZ was discussed. The experimental results indicate that the microstructnre of the CGHAZ is only the granular bainite which consists of bainitic ferrite (BF) lath and M-A constituent while t8/5 is 0.3-30 s. The M-A constituent consists of twinned martensite and residual austenite, and the change of the volume fraction of the residual austenite in the M-A constituent is very small when t8/5 is between 0.3 and 30 s. The morphology of the M-A constituent obviously changes with the variation of t8/5.As t8/5 increases, tile average width, gross and shape parameter of the M-A constituent increase, while the line density of the M-A constituent decreases.展开更多
The experimental research on refining slag systems for ultra-low sulphur steel was carried out in a 10 kg induction furnace.It was proved that sulphur element in molten steel can be removed to less than 5×10^(-6)...The experimental research on refining slag systems for ultra-low sulphur steel was carried out in a 10 kg induction furnace.It was proved that sulphur element in molten steel can be removed to less than 5×10^(-6) by adding CaO-Al_2O_3-SiO_2-MgO-CaF_2 slag on the surface of molten steel and feeding CaO-BaO-CaF2 wire into molten steel.And L_s,which is the coefficient of sulphur between slag and molten steel,that is ω(s)/ω[s],increases by increasing I(I = ωBaO/ωCaO).When I=5/3,L_s can be up to its maximum of 633.The CaSi is effective for deep desulphurization,especially when it is added to the slag of wire feeding.展开更多
Integral thin shells made of high strength aluminum alloys are urgently needed in new generation transportation equipment. There are challenges to overcoming the co-existing problems of wrinkling and splitting by the ...Integral thin shells made of high strength aluminum alloys are urgently needed in new generation transportation equipment. There are challenges to overcoming the co-existing problems of wrinkling and splitting by the cold forming and hot forming processes. An innovative technology of ultra-low temperature forming has been invented for aluminum alloy thin shells by the new phenomenon of ‘dual enhancement effect’. That means plasticity and hardening are enhanced simultaneously at ultra-low temperatures. In this perspective, the dual enhancement effect is described, and the development, current state and prospects of this new forming method are introduced. This innovative method can provide a new approach for integral aluminum alloy components with large size, ultra-thin thickness, and high strength. An integral tank dome of rocket with 2 m in diameter was formed by using a blank sheet with the same thickness as the final component, breaking through the limit value of thickness-diameter ratio.展开更多
This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient ...This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient under different conditions were carried out.Results showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between materials.Biot's coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as well.Generally,Biot's coefficient remains stable with increased temperature.Lithology,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's coefficient.For strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's coefficient.For skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's coefficient.The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.展开更多
Given its relevance to the exploitation of ultra-low permeability reservoirs,which account for a substantial proportion of the world’s exploited and still unexploited reserves,in the present study the development of ...Given its relevance to the exploitation of ultra-low permeability reservoirs,which account for a substantial proportion of the world’s exploited and still unexploited reserves,in the present study the development of an adequate water injection system is considered.Due to the poor properties and weak seepage capacity of these reservoirs,the water injection pressure typically increases continuously during water flooding.In this research,the impact on such a process of factors as permeability,row spacing,and pressure gradient is evaluated experimentally using a high-pressure large-scale outcrop model.On this basis,a comprehensive evaluation coefficient is introduced able to account for the effective driving pressure.展开更多
Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline...Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes(mMWCNT)were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm^(-2) for the MEA with mMWCNT was obtained at an ultra-low loading of 120μg·cm^(-2) Pt/PtRu(both cathode and anode),which was 44.7%higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.展开更多
The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal ...The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.展开更多
Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure ...Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.展开更多
Deep rock mass tends to be broken into blocks when mining for materials deep below the surface.The rock layer of the roof of the mine can be regarded as a system of blocks of fractured rock mass.When subjected to high...Deep rock mass tends to be broken into blocks when mining for materials deep below the surface.The rock layer of the roof of the mine can be regarded as a system of blocks of fractured rock mass.When subjected to high ground stress and mining-induced disturbance,the efect of the ultra-low friction of the block system easily becomes apparent,and can induce rock burst and other accidents.By taking the block of rock mass as research object,this study developed a test system for ultra-low friction to experimentally examine its efects on the broken blocks under stress wave-induced disturbance.We used the horizontal displacement of the working block as the characteristic parameter refecting the efect of ultra-low friction,and examine its characteristic laws of horizontal displacement,acceleration,and energy when subjected to the efects of ultra-low friction by changing the frequency and amplitude of the stress wave-induced disturbance.The results show that the frequency of stress wave-induced disturbance is related to the generation of ultra-low friction in the broken block.The frequency of disturbance of the stress wave is within 1–3 Hz,and signifcantly increases the maximum acceleration and horizontal displacement of the broken blocks.The greater the intensity of the stress wave-induced disturbance is,the higher is the degree of block fragmentation,and the more likely are efects of ultra-low friction to occur between the blocks.The greater the intensity of the horizontal impact load is,the higher is the degree of fragmentation of the rock mass,and the easier it is for the efects of ultra-low friction to occur.Stress wave-induced disturbance and horizontal impact are the main causes of sliding instability of the broken blocks.When the dominant frequency of the kinetic energy of the broken block is within 20 Hz,the efects of ultra-low friction are more likely.展开更多
In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever mo...In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.展开更多
An ultra-low quiescent current low-dropout regulator with small output voltage variations and improved load regulation is presented in this paper. It makes use of dynamically-biased shunt feedback as the buffer stage ...An ultra-low quiescent current low-dropout regulator with small output voltage variations and improved load regulation is presented in this paper. It makes use of dynamically-biased shunt feedback as the buffer stage and the LDO regulator can be stable for all load conditions. The proposed structure also employs a momentarily current-boosting circuit to reduce the output voltage to the normal value when output is switched from full load to no load. The whole circuit is designed in a 0.18 μm CMOS technology with a quiescent current of 550 nA. The maximum output voltage variation is less than 20 mV when used with 1 μF external capacitor.展开更多
Microwave-absorbing polymeric composites based on single-walled carbon nanotubes (SWNTs) are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption...Microwave-absorbing polymeric composites based on single-walled carbon nanotubes (SWNTs) are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption perfor- mances in a range of 2 GHz-18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT-epoxy composites (1.3-mm thickness) with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appro- priate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.展开更多
基金supported by the Forward Looking Basic Major Scientific and Technological Projects of CNPC (Grant No.2021DJ2202).
文摘Ultra-low permeability reservoirs are characterized by small pore throats and poor physical properties, which areat the root of well-known problems related to injection and production. In this study, a gas injection floodingapproach is analyzed in the framework of numerical simulations. In particular, the sequence and timing of fracturechanneling and the related impact on production are considered for horizontal wells with different fracturemorphologies. Useful data and information are provided about the regulation of gas channeling and possible strategiesto delay gas channeling and optimize the gas injection volume and fracture parameters. It is shown that inorder to mitigate gas channeling and ensure high production, fracture length on the sides can be controlled andlonger fractures can be created in the middle by which full gas flooding is obtained at the fracture location in themiddle of the horizontal well. A Differential Evolution (DE) algorithm is provided by which the gas injectionvolume and the fracture parameters of gas injection flooding can be optimized. It is shown that an improvedoil recovery factor as high as 6% can be obtained.
文摘The glass-ceramics were prepared with the spodumene mineral as the main raw material,and the effects of ZrO_(2)replacing TiO_(2)on the samples were systematically investigated.The results show that the substitution of ZrO_(2)for TiO_(2)is not conductive to precipitate𝛽β-quartz solid solution phase,but can improve the transparency and flexural strength of glass-ceramics.And the glass-ceramic with the highest visible light transmittance(87%)and flexural strength(231.80 MPa)exhibits an ultra-low thermal expansion of-0.028×10^(-7)K^(-1)in the region of 30-700℃.
基金the Natural Science Foundation of Hubei Province of China(No.2020CFB860)。
文摘Through the rapid carbonation test of SFRRC with different fiber volume fractions at ultralow temperature,the influence of ultra-low temperature damage on the carbonation resistance of SFRRC was analyzed,which provides a theoretical basis for the application of SFRRC in ultra-low temperature engineering.The experimental results show that ultra-low temperatures can significantly weaken the carbonization resistance of SFRRC.When the temperature reaches 160℃,the carbonization depth increases by 67.66%compared with the normal state.The proper amount of steel fiber has an evident influence on the carbonation resistance of the material.However,when the addition amount exceeds the optimum content,the carbonation resistance of the material decreases.The grey prediction model established by constructing the original sequence can reasonably predict the carbonation resistance of SFRRC after ultra-low temperatures.
基金supported by the National Natural Science Foundations of China(21965024,22269016,51721002)the Inner Mongolia funding(2020JQ01,21300-5223601)the funding of Inner Mongolia University(10000-21311201/137,213005223601/003,21300-5223707)。
文摘Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.
基金Financial support for this work from National Sciencetechnology Support Plan Projects (No. 2012BAC26B00)the Science Foundation of China University of Petroleum, Beijing (No.2462012KYJJ23)
文摘Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.
基金financially supported by the Fundamental Research Funds for the Central Universities (No. FRF-TP-16-079A1)the National Science Foundation for Young Scientists of China (No. 51704021)+1 种基金the Joint Funds of National Natural Science Foundation of China (No. U1560203)supported by Beijing Key Laboratory of Special Melting and Preparation of High-end Metal Materials
文摘Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.
基金supported by Open Fund (PLC201203) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology)Major Project of Education Department in Sichuan Province (13ZA0177)
文摘Due to inherent limits of data acquisition and geophysical data resolution, there are large uncertainties in the characterization of subsurface fractures. However, outcrop analogies can provide qualitative and quantitative information on a large number of fractures, based on which the accuracy of subsurface fracture characterization can be improved. Here we take the tectonic fracture modeling of an ultra-low permeability sandstone reservoir based on an outcrop analogy, a case study of the Chang6t~ Formation of the Upper Triassic Yanchang Group of the Wangyao Oilfield in the Ordos Basin of China. An outcrop at the edge of the basin is a suitable analog for the reservoir, but the prerequisite is that they must have equivalent previous stress fields, similar final structural characteristics, relative timing and an identical depositional environment and diagenesis. The relationship among fracture density, rock type and bed thickness based on the outcrop is one of the most important fracture distribution models, and can be used to interpret fracture density in individual wells quantitatively. Fracture orientation, dip, geometry and scale, also should be described and measured in the outcrop, and can be used together with structure restoration and single well fracture density interpretation to guide fracture intensity prediction on bed surfaces and to constrain the construction of the 3D fracture geometry model of the subsurface reservoir. The application of the above principles shows the outcrop-based tectonic fracture models of the target ultra-low permeability sandstone reservoir are consistent with fractures inferred from microseismic interpretation and tracer tests. This illustrated that the fracture modeling based on the outcrop analogy is reliable and can reduce the uncertainty in stochastic fracture modeling.
文摘800 MPa grade new ultra-low carbon bainitic (NULCB) steel is the recently developed new generation steel. The microstructure in the coarse-grained heat affected zone (CGHAZ) of NULCB steel under laser welding conditions was investigated by thermal simulation. The influence of the cooling time from 800℃ to 500℃.t8/5 (0.3-30 s), on the microstructure of the CGHAZ was discussed. The experimental results indicate that the microstructnre of the CGHAZ is only the granular bainite which consists of bainitic ferrite (BF) lath and M-A constituent while t8/5 is 0.3-30 s. The M-A constituent consists of twinned martensite and residual austenite, and the change of the volume fraction of the residual austenite in the M-A constituent is very small when t8/5 is between 0.3 and 30 s. The morphology of the M-A constituent obviously changes with the variation of t8/5.As t8/5 increases, tile average width, gross and shape parameter of the M-A constituent increase, while the line density of the M-A constituent decreases.
基金Item Sponsored by National Key Fundamental Research Development Project of China(G1998061500)
文摘The experimental research on refining slag systems for ultra-low sulphur steel was carried out in a 10 kg induction furnace.It was proved that sulphur element in molten steel can be removed to less than 5×10^(-6) by adding CaO-Al_2O_3-SiO_2-MgO-CaF_2 slag on the surface of molten steel and feeding CaO-BaO-CaF2 wire into molten steel.And L_s,which is the coefficient of sulphur between slag and molten steel,that is ω(s)/ω[s],increases by increasing I(I = ωBaO/ωCaO).When I=5/3,L_s can be up to its maximum of 633.The CaSi is effective for deep desulphurization,especially when it is added to the slag of wire feeding.
基金supported by the National Key Research and Development Program of China (No.2019YFA0708800)the Fundamental Research Funds for the Central Universities (No.DUT20ZD101)。
文摘Integral thin shells made of high strength aluminum alloys are urgently needed in new generation transportation equipment. There are challenges to overcoming the co-existing problems of wrinkling and splitting by the cold forming and hot forming processes. An innovative technology of ultra-low temperature forming has been invented for aluminum alloy thin shells by the new phenomenon of ‘dual enhancement effect’. That means plasticity and hardening are enhanced simultaneously at ultra-low temperatures. In this perspective, the dual enhancement effect is described, and the development, current state and prospects of this new forming method are introduced. This innovative method can provide a new approach for integral aluminum alloy components with large size, ultra-thin thickness, and high strength. An integral tank dome of rocket with 2 m in diameter was formed by using a blank sheet with the same thickness as the final component, breaking through the limit value of thickness-diameter ratio.
基金This work was supported by PetroChina Innovation Foundation(Grant No.2019D-5007-0214).
文摘This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient under different conditions were carried out.Results showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between materials.Biot's coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as well.Generally,Biot's coefficient remains stable with increased temperature.Lithology,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's coefficient.For strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's coefficient.For skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's coefficient.The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.
基金The authors gratefully acknowledge the financial support from the National Science and Technology Major Project of China(Grant Nos.2017ZX05013-001 and 2017ZX05069-003).
文摘Given its relevance to the exploitation of ultra-low permeability reservoirs,which account for a substantial proportion of the world’s exploited and still unexploited reserves,in the present study the development of an adequate water injection system is considered.Due to the poor properties and weak seepage capacity of these reservoirs,the water injection pressure typically increases continuously during water flooding.In this research,the impact on such a process of factors as permeability,row spacing,and pressure gradient is evaluated experimentally using a high-pressure large-scale outcrop model.On this basis,a comprehensive evaluation coefficient is introduced able to account for the effective driving pressure.
基金financial supports by the National Key Research and Development Program of China(2019YFB1504500)the National Natural Science Foundation of China(22078031,91834301,21761162015)+1 种基金the Fundamental Research Funds for the Central Universities,CQU(2020CDJQY-A032,2020CDJLHZZ064)the Natural Science Foundation of Chongqing(cstc2020jcyjmsxmX0637)。
文摘Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes(mMWCNT)were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm^(-2) for the MEA with mMWCNT was obtained at an ultra-low loading of 120μg·cm^(-2) Pt/PtRu(both cathode and anode),which was 44.7%higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.
基金financially supported by the Hebei Province Science and Technology Support Program(No.14211007D)
文摘The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.
基金finically supported by the National Natural Science Foundation of China(22075055)the Guangxi Science and Technology Project(AB16380030)the Innovation Project of Guangxi Graduate Education(YCSW2020052)。
文摘Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.
基金supported by the National Science Foundation of China(51974148)the Liaoning Xingliao Talent Program(XLYC1807130).
文摘Deep rock mass tends to be broken into blocks when mining for materials deep below the surface.The rock layer of the roof of the mine can be regarded as a system of blocks of fractured rock mass.When subjected to high ground stress and mining-induced disturbance,the efect of the ultra-low friction of the block system easily becomes apparent,and can induce rock burst and other accidents.By taking the block of rock mass as research object,this study developed a test system for ultra-low friction to experimentally examine its efects on the broken blocks under stress wave-induced disturbance.We used the horizontal displacement of the working block as the characteristic parameter refecting the efect of ultra-low friction,and examine its characteristic laws of horizontal displacement,acceleration,and energy when subjected to the efects of ultra-low friction by changing the frequency and amplitude of the stress wave-induced disturbance.The results show that the frequency of stress wave-induced disturbance is related to the generation of ultra-low friction in the broken block.The frequency of disturbance of the stress wave is within 1–3 Hz,and signifcantly increases the maximum acceleration and horizontal displacement of the broken blocks.The greater the intensity of the stress wave-induced disturbance is,the higher is the degree of block fragmentation,and the more likely are efects of ultra-low friction to occur between the blocks.The greater the intensity of the horizontal impact load is,the higher is the degree of fragmentation of the rock mass,and the easier it is for the efects of ultra-low friction to occur.Stress wave-induced disturbance and horizontal impact are the main causes of sliding instability of the broken blocks.When the dominant frequency of the kinetic energy of the broken block is within 20 Hz,the efects of ultra-low friction are more likely.
基金the Ministry of Science and Technology of China(No.2016YFA0400302)the National Natural Sciences Foundation of China(Nos.11775142 and U1965201)the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP).
文摘In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.
文摘An ultra-low quiescent current low-dropout regulator with small output voltage variations and improved load regulation is presented in this paper. It makes use of dynamically-biased shunt feedback as the buffer stage and the LDO regulator can be stable for all load conditions. The proposed structure also employs a momentarily current-boosting circuit to reduce the output voltage to the normal value when output is switched from full load to no load. The whole circuit is designed in a 0.18 μm CMOS technology with a quiescent current of 550 nA. The maximum output voltage variation is less than 20 mV when used with 1 μF external capacitor.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB933401 and 2014CB643502)the National Natural Science Foundation of China(Grant Nos.21374050,51273093,and 51373078)
文摘Microwave-absorbing polymeric composites based on single-walled carbon nanotubes (SWNTs) are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption perfor- mances in a range of 2 GHz-18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT-epoxy composites (1.3-mm thickness) with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appro- priate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.