Study on Optimal Water ControlMethods for Horizontal Wells in Bottom Water Clastic Rock Reservoirs

The segmented water control technology for bottom water reservoirs can effectively delay the entry of bottom water and adjust the production profile.To clarify the impact of different methods on horizontal well production with different reservoir conditions and to provide theoretical support for the scientific selection of methods for bottom water reservoirs,a numerical simulation method is presented in this study,which is able to deal with wellbore reservoir coupling under screen tube,perforation,and ICD(Inflow Control Device)completion.Assuming the geological characteristics of the bottom-water conglomerate reservoir in the Triassic Formation of the Tahe Block 9 as a test case,the three aforementioned completion methods are tested to predict the transient production characteristics.The impact of completion parameters,reservoir permeability,bottom-water energy,and individual well control on the time to encounter water in horizontal wells(during a water-free production period)is discussed.A boundary chart for the selection of completion methods is introduced accordingly.The results show that the optimized ICD completion development effect for heterogeneous reservoirs is the best,followed by optimized perforation completion.Permeability is the main factor affecting the performances of completion methods,while bottom water energy and single well controlled reserves have a scarce impact.The average permeability of the reservoir is less than 500 mD,and ICD has the best water control effect.If the permeability is greater than 500 mD,the water control effect of perforation completion becomes a better option.

Derivation of Plastic Work Rate Done per Unit Volume for Mean Yield Criterion and Its Application

In Haigh Westergaard stress space linear combination of twin shear stress and Tresca yield functions is called the mean yield （MY） criterion. The mathematical relationship of the criterion and its plastic work rate done per unit volume were derived. A generalized worked example of slab forging was analyzed by the criterion and its corresponding plastic work rate done per unit volume. Then, the precision of the solution was compared with those by Mises and Twin shear stress yield criterions, respectively. It turned out that the calculated results by MY criterion were in good agreement with those by Mises criterion.

Temperature field analysis and its application in hot continuous rolling of Inconel 718 superalloy

A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continuous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method （FEM）. The temperature of characteristic analysis points in the intermediate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 ℃ and initial velocity in range of 0.15-0.55 m·s^-1. Based on finite element analysis and microstructural observation in cylindrical hot compression experiments, the appropriate hot continuous rolling technologies have been designed for rod products with different diameters. For a real rolling practice, the simulated surface temperature was examined and is in good agreement with the measured one.

Quantitative description of infrared radiation characteristics of preflawed sandstone during fracturing process

Previous studies show that infrared radiation temperature(IRT)abnormalities are always accompanied by the crack development in rocks under external loads.In this context,experiments were conducted on preflawed sandstone to investigate the infrared radiation characteristics during failure process.Two indicators were defined herein,i.e.coefficient of variation of IRT(CVIRT)and skewness of IRT(SIRT).The regression analysis shows that the IRT probability distributions during loading process fit the Gaussian model.The variations in the CVIRT are characterized by four stages:primary stage,steady stage,accelerating stage and post-peak stage.Besides,the variations in the SIRT are divided into three stages:primary stage,steady stage and failure and post-peak stage.The precursor point for preflawed rock failure is identified based on the CVIRTetime curve,with average precursor point of 83%of the peak stress.Compared with other IRT indicators,the proposed two IRT indicators have higher sensitivity to IRT abnormalities during failure process.Furthermore,the connection between the IRT indicators and the rock fracturing was investigated to interpret the IRT indicator abnormalities.Based on the Verhulst inverse function,a new quantitative model was presented to describe the primary stage,steady stage and accelerating stage of the CVIRTetime curve.The results obtained in this study can provide early-warning information for rock failure prediction.

Effect of Cooling History on Yield Ratio of Fine-grain Ferrite/Pearlite Steel

Effect of different cooling history on yield ratio of HP295 steel for welded gas cylinder was studied and the result implied that both fine microstructure and good mechanical properties can be attained by using two-stage cooling and controlling the coiling temperature. The yield ratio of HP295 steel sheet was reduced to less than 0.8 by twostage cooling process. The pass percent of yield ratio was enhanced from less than 90% to 100%. The mechanical properties satisfied the criteria of GB6653-1994.

Numerical Simulation of Two Types of Electromagnetic Edge Dam Used in Twin Roll Strip Casting

Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.

Modeling of Slab Induction Heating in Hot Rolling by FEM

FEM (Finite Element Method) has been widely used to solve temperature in hot rolling. The heat gen-erating rate of electromagnetic field has been discussed in order to improve the efficiency and accuracy in the solution of induction heating. A new heat generating rate model was proposed and derived from the calculated results by FEM software in consideration of work frequency, source current density, and the air gap between induction coil and slab. The calculated distribution of heat generating rate in the skin depth by the model is satisfying and reliable compared with that of FEM software. Then, the mathematic model of the heat generating rate model is considered as the density of heat reservoir to solve the temperature in induction heating. Moreover, the temperature evolution of slab in induction heating from a hot rolling plant has been solved by the developed FE code and the calculated temperature has a good agreement with the measured value. Therefore, the heat generating rate model is suitable and efficiency to solve the temperature in induction heating by FEM.

Recent Development on Theory and Application of Variable Gauge Rolling, a Review

Variable gauge rolling （VGR） is a new technology for producing the materials which have the advantage of lightweight due to optimized thickness according to load distribution. The new progresses in the theoretical research and application of VGR are reviewed in this paper. Two basic equations, VGR-f and VGR-s, were deduced. The former is a new differential equation of force equilibrium, and the latter is a new form of formula for the law of mass conservation. Both of them provide a new base for the development of VGR analysis. As the examples of VGR＇s application, tailor rolled blank （TRB） and longitudinal profile （LP） plate are introduced. Now TRBs are only produced in Germany and China, and have been used in the automotive manufacturing to play an important role in lightweight design. LP plates have been used in shipbuilding and bridge construction, and promised a bright prospect in reducing construction weight. In addition, new technologies and applications of VGR emerge constantly. Tailor welded strips and tailor rolled strips with variable thickness across the width can be used for progressive die and roll forming. The 3D profiled blank can be obtained by two-step rolling process. Tailor tubes witli the variable wail thickness are an efficient way to reduce the weight. The blank with tailored thickness and mechanical property is also under development. Above products based on the tailored ideas provide a new materials-warehouse for the designers to select so as to meet the needs of weight reducing and material saving.

Static Recrystallization and Precipitation Behavior of a Weathering Steel Microalloyed with Vanadium

The static recrystallization （SRX） and precipitation behavior of a weathering steel microalloyed with vanadium were investigated through double-pass compression tests under controfled conditions using the MMS-300 thermal-mechanical simulator. The deformation temperatures ranged from 800 °C to 1000 °C, and the inter- pass time from 1 s to 500 s. The simulation results showed that SRX occurred after 5-10 s at the first compression deformation. The softening fraction of SRX was found to increase with increasing the deformation temperature and the pre-strain. However, the softening fraction scarcely changed during the process of strain-induced precipitation. In addition, the kinetics of SRX was described by the Avrami equation, and the Avrami exponent appeared to be closely associated with the deformation temperature. The microstructure evolution was investigated at the initiation and completion of recrystallization. The amount and distribution of the precipitates were analyzed. The relationship between the driving force of SRX and the pinning force of precipitation was discussed. Besides, the recrystallization inhibition was detected at the early stage of precipitation, and the pinning forces were found to be of a magnitude comparable to the driving force. Moreover, the pinning forces were found to increase with the degree of precipitation and reach a peak at the intermediate stage of precipitation, and finally reduce as the particles coarsened.

Effect of Austempering Route on Microstructural Characterization of Nanobainitic Steel

A low-temperature nanobainitic steel was obtained through one-step and two-step austempering. The effect of austempering temperature, time, and route on bainitic lath width, volume fraction of retained austenite, carbon concen- tration in retained austenite, and nanohardness of bainitic lath and retained austenite was studied. Results showed that the transformation kinetics was slowed down and the bainitic lath was refined as the austempering temperature decreased from 300 to 250 C. Both coarser and finer bainitic laths were obtained with the two-step austempering, which was consistent with the lath size at 300 and 250 C austempering, respectively. X-ray diffraction analysis showed that both volume fraction of retained austenite and its carbon concentration decreased with the decrease of austempering temperature for the one-step austempering, and especially the carbon concentration is obviously increased when the two-step austempering is adopted. The nanohardness of the bainitic lath in the sample after two-step austempering treated lies between that of the samples after 300 and 250 C austempering treated. The product of tensile strength and total elongation of the two-step austempered sample is the highest, which increases monotonously with the product of retained austenite fraction and its carbon concentration. Higher strengthluctility balance may be resulted by the fine bainitic lath, high volume fraction, and high stability of retained austenite in the sample after two-step austempered.

Springback characteristics in U-channel forming of tailor rolled blank

Residual stress developed during the rolling process of tailor rolled blank （TRB） can affect the springback of finished parts considerably. Springback characteristics of unannealed and annealed TRBs were investigated by means of numerical simulation and experiments taking U-Channel as an example. TRBs were annealed by the annealing process （700 ℃, holding time 10 h）, then stamping and springback processes of unannealed and annealed TRBs were simulated, and corresponding experiments were also carried out. Effects of the transition zone length, the blank thickness, the friction coefficient and the die clearance on the springback of TRB were analyzed. The results demonstrate that the springback of TRB annealed at 700 ~C for 10 h re- duces significantly. For unannealed and annealed U-Channels, the springback of TRB U-Channel is in direct proportion to the die clearance and is in inverse proportion to the transition zone length, the blank thickness and the friction coefficient. Spring- backs of the thinner monolithic （uniform thickness） blank, the thinner side of TRB, the thicker side of TRB and the thicker monolithic blank are sorted in descending order.

Rietveld refinement, microstructure and high-temperature oxidation characteristics of low-density high manganese steels

Three forged low-density high manganese steels Mn28Al10,Mn28Al8 and Mn20Al10 were used as experimental materials in this study.The forged microstructure and external oxidation characteristics at 1323 K and 1373 K for 5-25 h in air were investigated by microstructural observation and X-ray diffraction（XRD）technique.The phase compositions and abundance in the forged and oxidized samples were quantitatively obtained by Rietveld method on the basis of XRD pattern analysis.The results showed that an austenitic microstructure formed in steels Mn28Al10 and Mn28Al8,and 18.02 wt%ferrite could be found in Mn20Al10.The relative amount of ~5.28 wt%-carbide（Fe_3AlC_（0.5））in Mn28Al10 was far greater than that in Mn28Al8 and Mn20Al10.The oxidation kinetics of forged steels oxidized at 1323 K for 5-25 h had two-stage parabolic rate laws;and the oxidation rate of the first stage was lower than that of the second stage.When they were oxidized at 1373 K for 5-25 h,the oxidation kinetics followed only a parabolic law and the oxidation rates were respectively greater than those at 1323 K for 5-25 h.When they were oxidized at 1323 K for 25 h,detached external scales contained Fe_2MnO_4and-Fe_2O_3oxides.-Al_2O_3and（Fe,Mn）_2O_3oxides could only be indexed in steels Mn28Al8 and Mn28Al10,respectively.When they were oxidized at 1373 K for 25 h,Fe_2MnO_4,Fe_3O_4,-Fe_2O_3 and-Al_2O_3oxides could all be indexed in the external detached scales.The main phase of detached external scales was Fe_2MnO_4;and the relative amount of-Al_2O_3in steel Mn28Al8 was higher than that in steels Mn28Al10 and Mn20Al.The external oxidation layers of these three forged steels oxidized at 1323 K and 1373 K for 25 h were essentially followed the sequence of-Al_2O_3,Fe_2MnO_4,Fe_3O_4,FeMnO_3,and Fe_2O_3from the substrate to the outside surface.The forged Mn28Al10 steel with austenitic microstructure and a certain amount of-carbide（~5.28 wt%in the present work）possessed a better combination of strength,ductility,specific strength,and oxidation rate when compared to that of the forged Mn28Al8 and Mn20Al10 steels.

Graphene-wrapped MnCO_(3)/Mn_(3)O_(4) nanocomposite as an advanced anode material for lithium-ion batteries: Synergistic effect and electrochemical performances

Developing new electrode materials with a high specific capacity for excellent lithium-ion storage properties is very desirable.The MnCO_(3)/Mn_(3)O_(4)nanoparticles with uniform size(about 50 nm)and shape which are wrapped with graphene have been successfully synthesized via the one-step method for anode material of lithium-ion batteries.The as-prepared graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite exhibits remarkable electrochemical performance,including high reversible specific capacity,outstanding cycling stability,and excellent rate capability in comparison with the bare MnCO_(3)and MnCO_(3)/Mn_(3)O_(4)nanocomposite.This is because the synergistic effect of MnCO_(3)and Mn_(3)O_(4)nanoparticles and graphene nanosheets act as both electron conductors and volume buffer layers.From the scanning electron microscopy(SEM)analysis,we confirmed that the morphology and structure of the composite are preserved after 200 cycles.This further confirms that graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite acts as a stable template for reversible lithium-ion intercalation/deintercalation.

Smart luminescent solar concentrator as a BICPV window

Building integrated concentrating photovoltaic(BICPV)windows have attracted numerous studies in recent years.However,there is a tradeoff between the light transmittance and power generation efficiency in the design of BICPV window.In this paper,a smart luminescent solar concentrator(LSC)is introduced as the BICPV window.The proposed smart LSC system features on the combination of fluorescent dyes with thermochromic materials to enhance photoelectric conversion efficiency as well as form a dynamic response mechanism to ambient solar radiation and environmental temperature.In this study,a BICPV smart window system consists of the waveguide doped with organic dye Lumogen F Red-305(BASF)and the thermochromic hydrogel membrane has been developed.The research on analytic design parameters is executed through optical simulation by ray tracing technology along with outdoor comparative experiments.From simulations for a smart LSC of 100 mm×100 mm×3 mm with a bottom-mounted solar cell of 100 mm×10 mm,the optical effective concentration is found to be with the range of 1.23 to 1.31 when a highest gain of 1.26 in power over the bare solar cell is obtained from experiments.

Existence and uniqueness of extreme point of total power rate functional for hot rolling problem with rigid-plastic SCM model

The total power rate functional for hot rolling problem with the rigid-plastic SCM model is considered. The gradient operator of the plastic deformation power rate functional is deduced. it is strictly monotone mapping. Further, it is proved that the frictional power rate functional is a convex functional and the tensional stress power rate functional is a linear one. Hence, the total power rate functional is a strictly convex functional. By using nonlinear functional analysis methods, the existence and uniqueness of extreme point of the functional is obtained.