Study on the clogging mechanism of punching screen in sand control by the punching structure parameters

As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.

Enhanced catalytic conversion of polysulfides using high-percentage 1T-phase metallic WS_(2) nanosheets for Li–S batteries

High-energy-density lithium-sulfur batteries has attracted substantial attention as competitive candidates for large-scale energy storage technologies.Still,the adverse“shuttle effect”and sluggish sulfur conversion reaction kinetics immensely obstruct their commercial viability.Herein,a two-dimensional metallic 1T phase WS_(2)(1T-WS_(2))nanosheets modified functional separator is developed to improve the electrochemical performance.Meanwhile,the semiconducting bulk-WS_(2) crystals,and 2H phase WS_(2)(2H-WS_(2))nanosheets with more basal-plane Svacancy defects are also prepared to probe the contributions of the crystal structure(phase),S-vacancy defects,and edges to the Li–S batteries performance experimentally and theoretically.In merits of the synergistic effect of high ion and electron conductivity,enhanced binding ability to lithium polysulfides(LiPSs),and sufficient electrocatalytic active sites,the 1T-WS_(2) shows highly efficient electrocatalysis of LiPSs conversion and further improves Li–S battery performance.As expected,thus-fabricated cells with 1T-WS_(2) nanosheets present superior cycle stability that maintain capacity decline of 0.039%per cycle after 1000 cycles at 1.0 C.The strategy presented here offers a viable approach to reveal the critical factors for LiPSs catalytic conversion,which is beneficial to developing advanced Li–S batteries with enhanced properties.

A MOF derived hierarchically porous 3D N‐CoP_(x)/Ni_(2)P electrode for accelerating hydrogen evolution at high current densities

Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demanded by industry still remain great challenge.Herein,taking advantage of the highly tunable metal‐organic framework(MOF)templates,nitrogen doped binary transition metal phosphides electrocatalysts(N‐CoP_(x)/Ni_(2)P)with three‐dimensional(3D)conductive network structure were successfully synthesized.The 3D open porous channels could expose more catalytically active sites;nitrogen doping and the synergistic effect between CoP and Ni_(2)P can increase the electron density of Co atoms at active sites,further optimizing the Gibbs free energy of hydrogen(ΔGH*)and water(ΔG_(H_(2)O*)).As a result,the obtained N‐CoP_(x)/Ni_(2)P catalyst exhibits extraordinary electrocatalytic activity in a wide pH range.Especially,it requires an extremely low overpotential of 152 mV to deliver a high current density of 650 mA cm^(–2) in alkaline media.This work may shed some light on the rational design of cheap electrocatalysts and electrode materials that work well at high current densities.

Study of the blocking mechanism in gravel packing based on CFD-DEM

Gravel packing sand control(GPSC),as the optimization of mechanical sand control technology,is widely used in the deep water completion and sand control of loose sandstone heavy oil reservoirs and highly argillaceous.To explore the blocking mechanism of GPSC,the influence of its structural parameters on the blocking of GPSC is investigated.This paper establishes a particle element model based on computational fluid dynamics-discrete element method coupling using the discrete element method and establishes a fluid flow model combined with computational fluid dynamics to realize their full coupling solution.And sand control experiments were carried out using a micro visual sand control simulation device to verify the blocking model.The blocking mechanism is analyzed from the microscopic point of view,and then,the influence of sand control structure parameters on the blocking in GPSC design is evaluated.The results show the following:(1)the blocking process of GPSC can be divided into three stages:an initial stage,sand accumulation stage,and equilibrium stage.(2)There are two main types of gravel packing blockage.The first type of blocking is blocking on the surface of the gravel layer.Sand particles on the surface of gravel layer mainly exist in the form of large particle size blocking gravel pores and sand particles bridging each other.The second type of blockage is the blockage inside the gravel layer.Sand particles mainly exist in the form of internal mud cakes and adsorption on gravels inside the gravel layer.(3)To ensure the sand control performance of the gravel layer,the gravel layer thickness is designed between 23 and 28 mm.The displacement or pressure of the on-site packing pump should be increased to ensure that the gravel layer packing solidity ranges between 59%and 62%.In the design of GPSC,it should be ensured that the median particle size of gravel is 5–6 times the median particle size of sand.This study provides an effective technical reference for the design of gravel structural parameters in on-site gravel packing completion sand control.

Partial AZFc duplications not deletions are associated with male infertility in the Yi population of Yunnan Province,China

Objective:There are many reports on associations between spermatogenesis and partial azoospermia factor c(AZFc) deletions as well as duplications;however,results are conflicting,possibly due to differences in methodology and ethnic background.The purpose of this study is to investigate the association of AZFc polymorphisms and male infertility in the Yi ethnic population,residents within Yunnan Province,ChinaMethods:A total of 224 infertile patients and 153 fertile subjects were selected in the Yi ethnic population.The study was performed by sequence-tagged site plus/minus(STS+/) analysis followed by gene dosage and gene copy definition analysis.Y haplotypes of 215 cases and 115 controls were defined by 12 binary markers using single nucleotide polymorphism on Y chromosome(Y-SNP) multiplex assays based on single base primer extension technology.Results:The distribution of Y haplotypes was not significantly different between the case and control groups.The frequencies of both gr/gr(7.6% vs.8.5%) and b2/b3(6.3% vs.8.5%) deletions do not show significant differences.Similarly,single nucleotide variant(SNV) analysis shows no significant difference of gene copy definition between the cases and controls.However,the frequency of partial duplications in the infertile group(4.0%) is significantly higher than that in the control group(0.7%).Further,we found a case with sY1206 deletion which had two CDY1 copies but removed half of DAZ genes.Conclusions:Our results show that male infertility is associated with partial AZFc duplications,but neither gr/gr nor b2/b3 deletions,suggesting that partial AZFc duplications rather than deletions are risk factors for male infertility in Chinese-Yi population.

Generation of shaping nondiffracting structured caustic beams on the basis of stationary phase principle

On the basis of the stationary phase principle,we construct a family of shaping nondiffracting structured caustic beams with the desired morphology.First,the analytical formula of a nondiffracting astroid caustic is derived theoretically using the stationary phase method.Then,several types of typical desired caustics with different shapes are numerically simulated using the obtained formulas.Hence,the key optical structure and propagation characteristics of nondiffracting caustic beams are investigated.Finally,a designed phase plate and an axicon are used to generate the target light field.The experimental results confirm the theoretical prediction.Compared with the classical method,the introduced method for generating nondiffracting caustic beams is high in light-energy utilization;hence,it is expected to be applied conveniently to scientific experiments.

Variable stiffness wires based on magnetorheological liquid metals

Magnetorheological fluid(MRF)has shown its great potential in the development of large mechanical devices,such as dampers,shock absorbers,rotary brakes,clutches,and prosthetic joints.Recently,more research focus has been invested on using MRF to develop soft,stretchable,and miniaturized devices with variable stiffness for realizing functionalities that cannot be achieved using solid smart materials.Here,based on liquid metal magnetoactive slurries(LMMS),a variable stiffness wire with excellent electrical conductivity is demonstrated.Without exposure to a magnetic field,the LMMS wire has an extremely low stiffness,and can be easily stretched while maintaining an excellent electrical conductivity.When applying a magnetic field,the wire becomes much stiffer and can retain its shape even under a load.The combination of properties of flexibility,high electrical conductivity,and variable stiffness of the wire is harnessed to make a flexible gripper that can grasp objects of various shapes.Moreover,by using gallium instead of its liquid metal alloys,the tunable stiffness range of the LMMS wire is signifi-cantly enhanced and can be controlled using both external magnetic fields and temperature-induced phase change.The presented LMMS wire has the potential to be applied in flexible electronics,soft robotics and so on.