A micro-crosslinked amphoteric hydrophobic association copolymer as high temperature-and salt-resistance fluid loss reducer for water-based drilling fluids

During ultradeep oil and gas drilling,fluid loss reducers are highly important for water-based drilling fluids,while preparing high temperature-and salt-resistance fluid loss reducers with excellent rheology and filtration performance remains a challenge.Herein,a micro-crosslinked amphoteric hydrophobic association copolymer(i.e.,DADC)was synthesized using N,N-dimethyl acrylamide,diallyl dimethyl ammonium chloride,2-acrylamido-2-methylpropane sulfonic acid,hydrophobic monomer,and pentaerythritol triallyl ether crosslinker.Due to the synergistic effects of hydrogen bonds,electrostatic interaction,hydrophobic association,and micro-crosslinking,the DADC copolymer exhibited outstanding temperature-and salt-resistance.The rheological experiments have shown that the DADC copolymer had excellent shear dilution performance and a certain degree of salt-responsive viscosity-increasing performance.The DADC copolymer could effectively adsorb on the surface of bentonite particles through electrostatic interaction and hydrogen bonds,which bring more negative charge to the bentonite,thus improving the hydration and dispersion of bentonite particles as well as the colloidal stability of the drilling fluids.Moreover,the drilling fluids constructed based on the DADC copolymer exhibited satisfactory rheological and filtration properties(FLHTHP=12 m L)after aging at high temperatures(up to200℃)and high salinity(saturated salt)environments.Therefore,this work provided new insights into designing and fabricating high-performance drilling fluid treatment agents,demonstrating good potential applications in deep and ultradeep drilling engineering.

Preparation and performance evaluation of the slickwater using novel polymeric drag reducing agent with high temperature and shear resistance ability

Slickwater fracturing fluids are widely used in the development of unconventional oil and gas resources due to the advantages of low cost,low formation damage and high drag reduction performance.However,their performance is severely affected at high temperatures.Drag reducing agent is the key to determine the drag reducing performance of slickwater.In this work,in order to further improve the temperature resistance of slickwater,a temperature-resistant polymeric drag reducing agent(PDRA)was synthesized and used as the basis for preparing the temperature-resistant slickwater.The slickwater system was prepared with the compositions of 0.2 wt%PDRA,0.05 wt%drainage aid nonylphenol polyoxyethylene ether phosphate(NPEP)and 0.5 wt%anti-expansion agent polyepichlorohydrindimethylamine(PDM).The drag reduction ability,rheology properties,temperature and shear resistance ability,and core damage property of slickwater were systematically studied and evaluated.In contrast to on-site drag reducing agent(DRA)and HPAM,the temperature-resistant slickwater demonstrates enhanced drag reduction efficacy at 90℃,exhibiting superior temperature and shear resistance ability.Notably,the drag reduction retention rate for the slickwater achieved an impressive 90.52%after a 30-min shearing period.Additionally,the core damage is only 5.53%.We expect that this study can broaden the application of slickwater in high-temperature reservoirs and provide a theoretical basis for field applications.

Reduced graphene oxide aerogel decorated with Mo_(2)C nanoparticles toward multifunctional properties of hydrophobicity,thermal insulation and microwave absorption

Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior microstructure,as well as good compatibility with other electromagnetic(EM)components.Herein,we realized the decoration of rGO aerogel with Mo_(2)C nanoparticles by sequential hydrothermal assembly,freeze-drying,and high-temperature pyrolysis.Results show that Mo_(2)C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio.The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo_(2)C nanoparticles,and more importantly,these nanoparticles regulate the EM properties of the rGO aerogel to a large extent.Although more Mo_(2)C nanoparticles may decrease the overall attenuation ability of the rGO aerogel,they bring much better impedance matching.At a molar ratio of 1:1,a desirable balance between attenuation ability and impedance matching is observed.In this context,the Mo_(2)C/r GO aerogel displays strong reflection loss and broad response bandwidth,even with a small applied thickness(1.7 mm)and low filler loading(9.0wt%).The positive effects of Mo_(2)C nanoparticles on multifunctional properties may render Mo_(2)C/r GO aerogels promising candidates for high-performance EWAMs under harsh conditions.

Synthesis and Performance of an Associative Anti-shear Drag Reducer Based on Hydrogen Bond Association of Dodecyl Methacrylate

Using K2S2O8-Na2SO3 as the redox initiation system,a hydrogen-bond-association-based dodecyl methacrylate system associative anti-shear drag reducer was synthesised by standard emulsion polymerisation.The reaction process was simple and gentle as well as safe and stable.Molecular design was carried out using molecular dynamics simulation methods.The results of infrared spectroscopy,thermogravimetric analysis,differential scanning calorimetry,gel chromatography,and laser light scattering showed that the reaction polymerisation was relatively complete,the product was uniform,the molecular weight distribution was controllable,and the synthesised polymer had good flexibility.The donor lauryl methacrylate-styrene-methacrylic acid(LMA-St-MAA)and acceptor lauryl methacrylate-styrene-dimethylaminoethyl methacrylate(LMA-St-DMA)polymers had an associative intermolecular interaction force,which increased the molecular cluster size of the associative system complex.The complex had good shear resistance,and the test results of the tube pump shear test showed that the synthesised associative oil-soluble polymer drag reduction system exhibited better drag reduction rate performance than poly-α-olefins over repeated cycles.The research results provide a reference plan for minimising the number of station-to-station inputs,thereby ensuring the stability of oil pipelines and reducing transportation costs.

Tracking Regulatory Mechanism of Trace Fe on Graphene Electromagnetic Wave Absorption

Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.

The main physical properties of planosol in maize(Zea mays L.) cultivation under different long-term reduced tillage practices in the Baltic region

The impact of sustainable reduced tillage （RT） on the physical properties of soil is well documented worldwide; however, there is no precise information about the influence of long-term RT or no-till （NT） on the soils at the boundary for grain maize-growing in the semi-humid subarctic climate conditions of the Baltic states, especially on the formation of a hard- ened upper soil layer （10-15 cm in depth） --＂loosening hardpan＂. This study was carried out at the Research Station of Aleksandras Stulginskis University, Lithuania from 2009-2012. The investigations were based on a long-term （since 1988） field experiment. The aim of the investigation was to ascertain the influence of reduced primary tillage on the main soil＇s physical properties. This study examined soils that were deep ploughing （DP）, shallow ploughing （SP）, deep cultivation （DC）, shallow cultivation （SC）, and no-till （NT）. Reducing the tillage intensity to NT had no significant effect on the structural soil＇s composition; however, the stability of the structure of the 〉1 and 〉0.25 mm-size fractions was significantly higher in the non-reversibly tilled （DC, SC） and NT plots. The penetration resistance of the DP soils was less after primary tillage and wintering, and became similar to the NT plots at the end of the maize growth season. After primary tillage and wintering, the soil moisture content in the upper soil layer （0-5 cm depth） of the NT plots was 17-49 and 16-18% higher than that in the DP. Long-term reduction of primary tillage up to NT generally had no significant effect on the moisture content and soil bulk density of the 0-10 and 10-20 cm layers. The results showed that long-term RT stabilized the physical quality of soil. Less soil penetration resistance was established in the DP plots compared to both RT and NT, however, indicators of the formation of a uniform ＂loosening hardpan＂ layer were not found. It is summarized that long-term RT or NT systems stabilize, or may increase, the physical quality of soil in crop cultivation with low inter-row coverage potential （maize）, and could be applied in semi-humid subarctic climate conditions as a good option to prevent soil degradation.

A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

Adhesive forces exist between soil and the surfaces of soil-engaging components; they increase working resistance and energy consumption. This paper tries to find an approach to reduce the adhesion and resistance of bulldozing plate. A simplified mechanical model of adhesion and resistance between soil and a non-smooth bulldozing plate is proposed. The interaction force between moist soil and a non-smooth bulldozing plate is analyzed. The pressure and friction distribution on the bulldozing plate are computed, and the anti-adhesive effect of a corrugated bulldozing plate is simulated numerically. Numerical results show that the wavy bulldozing plate achieves an effective drag reduction in moist soil. The optimal wavy shape of the corrugated bulldozing plate with the minimal resistance is designed. The basic principle of reducing soil adhesion of the non-smooth surface is discovered.

Pneumatic resistance network analysis and dimension optimization of high pressure electronic pneumatic pressure reducing valve

The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.

Reduced graphene oxide (RGO) reinforced Mg biocomposites for use as orthopedic applications: Mechanical properties, cytocompatibility and antibacterial activity

Magnesium(Mg) has attracted wide interest in orthopedic applications as they exhibit great biodegradability and strong biocompatibility,while corrosion is the main concern for Mg that should be addressed prior to biomedical applications. In this work, ZM31(Mg-3Zn-1Mn)/x RGO(x = 0, 0.5, 1 and 1.5 wt%) biocomposites were synthesized by semi-powder metallurgy method. The results showed that the RGO acting as an effective reinforcing filler to prevent deformation and showed better compressive strength(282.3 ± 9 MPa) and revealed enhancement in failure Strain(7.8 ± 2.1%) at 1 wt% RGO concentration compared to Mg alloy(244.5 ± 9 MPa and 7.1 ± 1.5%respectively). Moreover, fracture analysis indicated a more ductile fracture of the nanocomposites after the incorporation of RGO. Crack bridging, crack deflection and crack branching are dominant mechanisms for reinforcement of Mg-based containing RGO. Mg composites containing 0.5 wt% RGO showed a low corrosion rate(2.75 mm/year), while more incorporation of RGO resulted in an increased corrosion rate(4.38 mm/year). In addition, the degradation rate of ZM31 alloy(2.57 mg·cm-2·d-1) obviously decreased with the addition of 0.5 wt%RGO(1.84 mg·cm-2·d-1) in the SBF. Besides, continuous apatite layers were created on the composites in the SBF solution. Also, the cell culture examinations showed good cell viability and adhesion on composites with 0.5 and 1 wt% RGO, which was demonstrated by the SEM and MTT assay The alkaline phosphatase(ALP) activity of the ZM3–0.5RGO composite was considerably higher than that of ZM31matrix alloy in 24 h and 48 h, implying higher osteoblastic differentiation. The antibacterial behavior toward both bacteria(E. coli and S.aureus) exhibited that escalating RGO concentration in Mg-matrix composites leads to further inhibition of bacteria growth. These findings suggested that ZM31–0.5RGO biocomposite could be a more promising candidate for orthopedic implants.

Food Losses and Food Waste in the Context of Sustainable Development of the Food Sector

Globally, about one third of all food produced is wasted every year. Losses take place along the entire food chain and they need to be analyzed and monitored due to their impact on the development of the food sector. In addition to quantitative losses, irrational use of food contributes to the depletion of natural resources （water and energy） and poses a threat to the environment, constituting a barrier to sustainable development of the food sector. The aim of this study was to establish the causes and effects of food waste throughout the food supply chain and to propose mitigation measures. Identified causes of food waste can be divided into two groups. The first are those that lead to the fact that food cannot be consumed （e.g., inadequate conditions of agricultural production and interruption of the cold chain）. In the second, those that cause food cannot be sold （e.g., wrong label and wrong product weight）. Most of the identified causes of food waste can be avoided （e.g., by improving the conditions of production, storage, and transportation）. However, it is not possible to eliminate all potential errors leading to food waste. It is therefore necessary to consider what action to take to use food as intended. One way to reduce losses and food waste can be re-distributing to charity.

Graphene resistive random memory - the promising memory device in next generation

Graphene-based resistive random access memory （GRRAM） has grasped researchers＇ attention due to its merits com- pared with ordinary RRAM. In this paper, we briefly review different types of GRRAMs. These GRRAMs can be divided into two categories： graphene RRAM and graphene oxide （GO）/reduced graphene oxide （rGO） RRAM. Using graphene as the electrode, GRRAM can own many good characteristics, such as low power consumption, higher density, transparency, SET voltage modulation, high uniformity, and so on. Graphene flakes sandwiched between two dielectric layers can lower the SET voltage and achieve multilevel switching. Moreover, the GRRAM with rGO and GO as the dielectric or electrode can be simply fabricated. Flexible and high performance RRAM and GO film can be modified by adding other materials layer or making a composite with polymer, nanoparticle, and 2D materials to further improve the performance. Above all, GRRAM shows huge potential to become the next generation memory.

Voltage-Dependent Electronic Transport Properties of Reduced Graphene Oxide with Various Coverage Ratios

Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low cost and precision. However, reduced graphene oxide(rGO) contains hydrogen and/or oxygen atoms hence the structure and properties of the rGO and intrinsic graphene are different. Considering the advantages of the implementation and utilization of rGO, voltage-dependent electronic transport properties of several rGO samples with various coverage ratios are investigated in this work. Ab initio simulations based on density functional theory combined with non-equilibrium Green's function formalism are used to obtain the current–voltage characteristics and the voltage-dependent transmission spectra of rGO samples. It is shown that the transport properties of rGO are strongly dependent on the coverage ratio. Obtained results indicate that some of the rGO samples have negative differential resistance characteristics while normally insulating rGO can behave as conducting beyond a certain threshold voltage. The reasons of the peculiar electronic transport behaviour of rGO samples are further investigated, taking the transmission eigenstates and their localization degree into consideration.The findings of this study are expected to be helpful for engineering the characteristics of rGO structures.

Resistance of Air Injection Transportation in a Cutter-suction Dredger

Cutter-suction dredger transports slurry through pipeline. But the pipeline is easy to be jammed and frayed because of huge resistance, resulting in limited exertion of dredger and high energy consumption. One of the solutions is air injection transporting, which can reduce the resistance in pipeline. This paper makes research on the relations between pipeline distance and other factors such as slurry concentration, pressure of air injection and transportation distance, by making use of Prof. Aluf Orell＇ s slug model. The test data prove that the key factors are slurry concentration and air volume fraction, and that high slurry concentration and low air volume fraction can reduce more resistance, and such reducing effect becomes weaker with the increase of transportation distance.

环保型改性纳米碳酸钙降滤失剂的合成与性能评价

纳米碳酸钙在钻井液中具有降滤失及封堵作用、且环保,但分散性差、易团聚,导致效果不理想。使用硅烷偶联剂对纳米碳酸钙进行表面改性,再通过自由基共聚法将抗温、抗盐单体接枝到改性纳米碳酸钙表面,得到改性纳米碳酸钙降滤失剂SDNPJ-2,采用红外光谱(FTIR)、热重分析进行表征,同时对比评价其综合性能,通过对膨润土基浆粒径、zeta电位分析,滤饼扫描电镜(SEM)分析,考察SDNPJ-2在黏土颗粒上的吸附特征,研究改性纳米碳酸钙降滤失剂在水基钻井液中的降滤失机制。结果表明:SDNPJ-2可抗230℃高温;1%SDNPJ-2可分别使4%膨润土基浆、25%盐水基浆、10%CaCl_(2)基浆150℃/(16 h)老化后的API滤失量降低70%、89%和85%,可抗氯化钠250000 mg/L、抗氯化钙100000 mg/L,降滤失效果优于国外同类目前最优产品Driscal D;生化需氧量(BOD_(5))为558 mg/L、BOD_(5)/COD(化学需氧量)达22.6%,可生物降解;SDNPJ-2通过酰胺基团吸附于黏土表面、改善其分散性,优化体系粒径级配、通过物理堆积有效封堵滤饼和地层孔隙,两方面协同达到优良的降滤失效果。

AMPS/DMAEMA/AM三元共聚物钻井液降滤失剂的研制

以丙烯酰胺、2-丙烯酰胺-2-甲基丙磺酸和甲基丙烯酸二甲氨基乙酯为单体,过硫酸铵为引发剂,采用水溶液聚合法制备了PAAD降滤失剂,通过单因素实验对其制备工艺进行了优化,并对降滤失剂的耐温耐盐性能进行了探究。结果表明,在丙烯酰胺、2-丙烯酰胺-2-甲基丙磺酸和甲基丙烯酸二甲氨基乙酯质量比为4∶2∶0.02、反应温度为60℃、反应时间4 h、过硫酸铵用量为混合单体质量的0.15%的最佳条件下,所制备的降滤失剂的降滤失效果最佳,抗温达210℃。

基于多臂结构抗高温高盐降滤失剂的合成及作用机制

以季戊四醇烯丙基醚为核心,合成具有多臂结构的超支化聚合物降滤失剂JHPAN,研究和分析JHPAN配制的钻井液在高温、高盐条件下的流变性能、降滤失性能和降滤失作用机制。结果表明:在加量(质量分数)为1.0%时,220℃老化前后,淡水浆的表观黏度分别为10.5和10.0 mPa·s,塑性黏度分别为9.0和11.0 mPa·s,动切力分别为1.5和1.0 Pa;在加量为1.0%时,220℃老化16 h后,饱和NaCl盐水浆的API滤失量和高温高压滤失量分别为11.8和25.5 mL;JHPAN的多臂结构中含有大量的吸附基团和抗温耐盐基团有助于钻井液高温、高盐环境下形成致密的泥饼,从而提升其降滤失效果。

抗220℃高温两性离子聚合物降黏剂的制备与性能

针对当前高温高密度水基钻井液流变性调控难题,基于分子结构优化设计和单体优选,制备了新型抗高温两性离子聚合物降黏剂HP-THIN。通过正交实验与单因素实验相结合的方法,对HP-THIN的制备条件进行了优化。采用红外光谱仪、乌氏黏度计和热重分析仪等分别对HP-THIN的分子结构、热稳定性以及相对分子质量进行表征和测定,研究了HP-THIN在220℃超高温条件下对淡水浆、盐水浆、含钙浆和高密度复合盐水浆等不同类型钻井液基浆的降黏性能。在室温下,测试了HP-THIN对基浆黏土颗粒吸附能力、Zeta电位和粒径的影响,并与国内外同类产品(Polythin和xy-27)进行了对比。结果表明,合成降黏剂HP-THIN的反应温度为60℃,反应时间为3 h,引发剂用量和链转移剂用量均为反应单体总量的1%,单体总质量分数为30%;单体AM、AA、AMPS、PTM物质的量比为1.9∶7.5∶2.1∶1。该聚合物的分子结构中含有设计官能团,其黏均相对分子质量约为8211,且具有较好的热稳定性。220℃老化后,HP-THIN在最优加量(0.3%)下对淡水基浆、盐水基浆、含钙基浆和高密度复合盐水基浆的降黏率分别达86%、72%、73%和51%,HP-THIN对不同类型钻井液基浆的高温降黏效果均优于国内外同类产品,相对于xy-27和Polythin,降黏剂HP-THIN对基浆黏土吸附能力强、Zeta电位绝对值大、黏土颗粒尺寸小,可以更好地消除黏土颗粒间网状结构,降低钻井液黏度,具有良好的应用前景。

基于发电机定子接地燃弧电阻变化特征的主动降压熄弧机理与抑制方法

定子接地燃弧故障是制约大型发电机安全可靠运行的技术瓶颈。为解决定子绕组接地电弧引发的绝缘击穿与铁心损伤问题,该文提出基于发电机定子接地燃弧电阻变化特征的柔性接地主动降压熄弧方法。该文建立了定子接地燃弧电阻与弧道电压的解析关系,揭示了定子接地故障点电压降低过程中,接地燃弧电阻增大的变化规律;明确了将接地故障点电压抑制在电弧重燃电压以下时,可实现定子绕组击穿间隙回归正常绝缘状态的抑制方法。根据大型发电机定子柔性接地方式降压熄弧策略,在接地故障燃弧阶段,中性点电压源输出故障点工频与3次谐波反向电势,主动降低故障点电压,将故障点电压降低至燃弧电压以下,使定子接地电弧熄灭。利用注入信号感知定子接地燃弧状态,实时监测定子阻尼率矢量角变化趋势,判定降压消弧过程中接地燃弧故障是否消除。所提方法无需将故障点电压降低至零,可有效降低非故障相电压抬升,降低定子非故障相绕组槽内击穿风险。在PSCAD/EMTDC仿真环境模拟定子接地故障燃弧工况,对所提方法进行试验验证。试验结果表明,基于定子接地燃弧电阻变化特征的柔性接地消弧方法可主动降低定子接地故障点电压,助增故障点间隙绝缘电阻回归,抑制接地电弧重燃,降低定子非故障相绝缘击穿风险,实现定子接地燃弧故障的可靠消弧。

基于缩尺模型的高铁桥梁预应力损失试验研究

【目的】为更好的评估在役预应力混凝土桥梁结构预应力损失状况。【方法】选用国内高铁中应用最广的32 m预应力混凝土箱梁作为研究对象,按照1:16的缩尺比例将箱梁转化为T形截面制作了26根C50混凝土试验模型梁。通过对试验梁预应力钢绞线应变、伸长量的瞬时和长期监测得到预应力损失的实际值,并将此实际值与目前国内外常用预应力损失规范计算所得值进行对比分析。【结果】预应力损失主要发生在前期即瞬时损失,约占总损失的70%;84.6%的试验梁锚固损失占瞬时损失总和的70%以上,最高达80.57%;试验梁的长期损失在锚固后的前10 d内变化较快,后期逐渐趋于稳定;将5种规范的计算结果与试验实测值进行对比,对于长期损失,数据显示实测数据与《铁路桥涵设计规范》(TB 10002—2017)计算结果最为吻合。【结论】研究结果可为实际工程中预应力梁的预应力损失计算提供参考。