Preparation of a functional fracturing fluid with temperature-and salt-resistance,and low damage using a double crosslinking network

Fracturing fluids(FFs)have been widely used to stimulate the tight reservoir.However,current FFs will not only lose their rheological property at high temperatures and high salt but also show an incomplete gel-breaking property.Herein,a double crosslinking network FF with pretty superiorities in rheology and low damage to the core was constructed by introducing both physical crosslinking and chemical crosslinking into the system.The construction of double crosslinking networks enhanced the rheology of this functional FF.The particle sizes of gel-breaking fluids are mainly distributed in 1.0e10,000 nm;furthermore,for every 10,000 mg/L increase in salinity,the particle size of the gel-breaking fluid is decreased by almost half.The adsorption capacity(<1.0 mg/g)gradually decreased with the increase of salinity at 20℃.Moreover,the adsorption of gel-breaking fluids on the rock decreased first and then kept stable with temperature increasing at a salinity of ≤30,000 mg/L,however,showed the opposite trend at 40,000 mg/L.The results of rheology,particle size,static adsorption,and core damage showed that this functional FF could be an alternative for the stimulation of a tight reservoir with high temperature and recycling of produced water with high salinity.

Comparative analysis of the gut microbiota of wild adult rats from nine district areas in Hainan,China

BACKGROUND Wild rats have the potential to hold zoonotic infectious agents that can spread to humans and cause disease.AIM To better understand the composition of gut bacterial communities in rats is essential for preventing and treating such diseases.As a tropical island located in the south of China,Hainan province has abundant rat species.Here,we examined the gut bacterial composition in wild adult rats from Hainan province.METHODS Fresh fecal samples were collected from 162 wild adult rats,including three species(Rattus norvegicus,Leopoldamys edwardsi,and Rattus losea),from nine regions of Hainan province between 2017-2018.RESULTS We analyzed the composition of gut microbiota using the 16S rRNA gene amplicon sequencing.We identified 4903 bacterial operational taxonomic units(30 phyla,175 families,and 498 genera),which vary between samples of different rat species in various habitats at various times of the year.In general,Firmicutes were the most abundant phyla,followed by Bacteroidetes(15.55%),Proteobacteria(6.13%),and Actinobacteria(4.02%).The genus Lactobacillus(20.08%),unidentified_Clostridiales(5.16%),Romboutsia(4.33%),unidentified_Ruminococcaceae(3.83%),Bacteroides(3.66%),Helicobacter(2.40%)and Streptococcus(2.37%)were dominant.CONCLUSION The composition and abundance of the gut microbial communities varied between rat species and locations.This work provides fundamental information to identify microbial communities useful for disease control in Hainan province.

A Semi-Looped-Functional for Stability Analysis of Sampled-Data Systems

Dear Editor, In recent decades, owing to the significance of sampled-data control way on reducing the burden of communication transmission and improving the control capability of networked control systems, the research of sampled-data systems has become increasingly important(see [1]–[5]).

沉水植物对水流结构与泥沙淤积的影响

为了研究水生植物对水流结构和泥沙淤积的影响,针对不同布置的沉水植物进行33组浑水水槽试验.结果表明,矮株植物区流速冠顶下为二次多项式分布,以上为对数分布;考虑相对株距的影响,建立矮株植物区紊动强度的双高斯垂线分布公式,按该公式计算的流速和紊动强度与实测资料较吻合.高株植物区流速呈“C”型分布,紊动强度以冠顶附近最大.3种株距布置时,混合植物冠顶以下平均流速为无植物时的32.5%~72.3%.提出小弗汝德数(Fr≤0.18)条件下矮株植物区相对淤积增量与水流强度和相对株距的非线性关系.在相同水流和株距下,混合植物淤积量高达无植物时的7倍,高株植物次之,随着株距的减小促淤效果逐渐增强.

基于静电纺丝技术PAN基碳纳米纤维膜性能及应用研究进展

主要介绍了近年来国内外研究学者利用静电纺制备聚丙烯腈(PAN)基碳纳米纤维膜工艺过程,主要包括纳米纤维膜的制备、预氧化和炭化等工序。另外,还综述了PAN基碳纳米纤维膜的性能优化方法及其应用进展。

高压和锰添加对流变挤压成形过共晶Al-Si合金富铁相和力学性能的影响（英文）

研究高压和锰添加对流变挤压成形Al-14Si-2Fe合金富铁相和力学性能的影响。首先,将半固态合金熔体进行超声振动处理,然后挤压成形。结果显示,当挤压力为0 MPa时,无超声挤压成形的Al-14Si-2Fe-(0.4,0.8)Mn合金铸态组织中的富铁相主要由粗大β-Al_5(Fe,Mn)Si相、δ-Al_4(Fe,Mn)_3Si_2相和骨骼状α-Al_(15)(Fe,Mn)3Si_2相组成。在流变挤压成形下,富铁相首先被超声振动细化,然后压力下的凝固使其尺寸进一步减小。在α相的形成过程中发生包晶反应。当合金成分相同时,流变挤压成形试样比无超声挤压成形试样的抗拉强度高;当成形工艺相同时,Al-14Si-2Fe-0.8Mn合金比Al-14Si-2Fe-0.4Mn合金的抗拉强度高。

EP/CNTs-CF复合材料制备及工艺优化

为提高碳纤维(CF)复合材料层间剪切强度,探索了在CF二维织物上直接沉积碳纳米管(CNTs)制备准三维结构增强体的研究,利用扫描电子显微镜、比表面积及孔径分析仪研究了碳纳米管-碳纤维(CNTs-CF)结构,采用热熔胶膜法制备CNTs-CF织物环氧树脂(EP)预浸料,制备了生长CNTs前后两种二维织物增强EP复合材料,分析了两种复合材料结构和力学性能的差异,并优化了EP/CNTs-CF复合材料的成型工艺。结果表明,在80℃,0.490 MPa保压4 min的条件下,能够制备浸渍较完全、表面平整的CNTs-CF预浸料;相比CF/EP复合材料成型,EP/CNTs-CF复合材料成型过程中需要提前加压并提高成型压力,经过工艺优化后,EP/CNTs-CF的层间剪切强度较CF/EP的层间剪切强度提高10.2%。

Effects of high-pressure rheo-squeeze casting on the Fe-rich phases and mechanical properties of Al-17Si-(1,1.5)Fe alloys

The effects of high pressure rheo-squeeze casting(HPRC) on the Fe-rich phases(FRPs) and mechanical properties of Al-17 Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration(UV) and then formed by high-pressure squeeze casting(HPSC). The FRPs in the as-cast HPSC Al-17 Si-1 Fe alloys only contained a long, needle-shaped β-Al5 Fe Si phase at 0 MPa. In addition to the β-Al5 Fe Si phase, the HPSC Al-17 Si-1.5 Fe alloy also contained the plate-shaped δ-Al4 Fe Si2 phase. A fine, block-shaped δ-Al4 Fe Si2 phase was formed in the Al-17 Si-1 Fe alloy treated by UV. The size of FRPs decreased with increasing pressure. After UV treatment, solidification under pressure led to further refinement of the FRPs. Considering alloy samples of the same composition, the ultimate tensile strength(UTS) of the HPRC samples was higher than that of the HPSC samples, and the UTS increased with increasing pressure. The UTS of the Al-17 Si-1 Fe alloy formed by HPSC exceeded that of the Al-17 Si-1.5 Fe alloy formed in the same manner under the same pressure. Conversely, the UTS of the Al-17 Si-1 Fe alloy formed by HPRC decreased to a value lower than that of the Al-17 Si-1.5 Fe alloy formed in the same manner.

长贮存期低温固化环氧树脂基预浸料研究进展

主要介绍了长贮存期低温固化环氧树脂基预浸料研究进展,包括国内外低温固化预浸料的概况及固化剂的改性,着重介绍了咪唑类固化剂的化学改性、微胶囊固化剂和超支化化合物及分子筛等方法,并对未来发展趋势和应用前景进行了展望。

Fracture sealing performance of granular lost circulation materials at elevated temperature:A theoretical and coupled CFD-DEM simulation study

Lost circulation is a common downhole problem of drilling in geothermal and high-temperature,high-pressure(HTHP)formations.Lost circulation material(LCM)is a regular preventive and remedial measure for lost circulation.However,conventional LCMs seem ineffective in high-temperature formations.This may be due to the changes in the mechanical properties of LCMs and their sealing performance under high-temperature conditions.To understand how high temperature affects the fracture sealing performance of LCMs,we developed a coupled computational fluid dynamics-discrete element method(CFD-DEM)model to simulate the behavior of granular LCMs in fractures.We summarized the literature on the effects of high temperature on the mechanical properties of LCMs and the rheological properties of drilling fluid.We conducted sensitivity analyses to investigate how changing LCM slurry properties affected the fracture sealing efficiency at increasing temperatures.The results show that high temperature reduces the size,strength,and friction coefficient of LCMs as well as the drilling fluid viscosity.Smaller,softer,and less frictional LCM particles have lower bridging probability and slower bridging initiation.Smaller particles tend to form dual-particle bridges rather than single-particle bridges.These result in a deeper,tighter,but unstable sealing zone.Reduced drilling fluid viscosity leads to faster and shallower sealing zones.

法国困境企业保护制度研究及借鉴

破产重整是中国《破产法》立法研究与法律适用中的热点和难点问题。法国的破产法治比较发达,其困境企业保护制度以1984年《企业困境预防与和解清理法》为框架建立起来并由2003年《破产预防联合组织法》、2005年《企业保护法》等一系列法律加以完善。法国困境企业保护法为避免企业状况恶化而尽早采取应对措施的立法思想,以及相应的破产预警程序、企业困境预防组织、破产和解、破产保护程序等制度都非常有特色,对于中国依法处置"僵尸企业"、破产工作统一协调机制制度化以及完善中国破产法律制度有很强的借鉴意义。

Effect of V and N on Microstructures and Properties of Grade-70 Tire Cord Steel during Cold Drawing

Commercial grade-70 tire cord steel was microalloyed with V and N to explore the possibility of substituting V for C and the effect of V and N on cementite dissolution during cold drawing process.Tensile strength,elongation and torsion laps of cold-drawn wires were determined.Microstructures of secondary phases were studied by transmission electron microscopy(TEM)and energy dispersive spectroscopy(EDS).Saturation magnetization was measured by using a vibrating sample magnetometer(VSM)to evaluate cementite dissolution during cold drawing process.Experimental results showed that with the increase of V content,tensile strength increased,elongation slightly decreased,and the torsion laps of the cold-drawn wires decreased.Results also showed that with the increase of N content,apeak(increasing first and then decreasing)appeared in the tensile strength graph,and an increase of elongation and a decrease of torsion laps of the cold-drawn wires occured.N is soluble in ferrite when its content is low.The increase in the content of N to 82×10-6 will result in the precipitation of the V-containing secondary phases.Also,cementite tended to be stable during cold drawing process with the increase of V and N contents.Grade-80 tire cord steel can be replaced by grade-70 tire cord steel microalloyed with 0.086mass% V.

Reconstruction and prediction of capillary pressure curve based on Particle Swarm Optimization-Back Propagation Neural Network method

Capillary pressure curve plays a critical role in the reservoir evaluation.It is essential to reconstruct and predict capillary pressure curve properly.Many traditional capillary pressure correlations have been suggested in the literature.However,their major limitation is mainly applicable to homogenous reservoir,and the larger error will be caused when heterogeneous reservoir is dealt by using these mathematical correlations.This study aims at providing an important method based on Particle Swarm Optimization-Back Propagation Neural Network(PSO-BP neural network)to represent and predict capillary pressure curve for homogenous and heterogeneous reservoir.The combination of PSO algorithm and BP neural network converges quickly,which improves the accuracy and efficiency of simulation.In this paper,core samples from three blocks of the same marine-sand reservoir,whose porosity is between 0.6%and 20.0%and permeability is between 0.1mD and 6117mD,are investigated by PSO-BP neural network method and J-Function method respectively.The reconstruction and prediction results are compared with the results obtained by mercury intrusion method in laboratory.The results show that capillary pressure curves reconstructed and predicted by PSO-BP neural network method are in better agreement with mercury intrusion curves than J-Function method,with 0.1%e5%and 5%e8%relative error respectively,which can totally meet the in-situ requirements.It is also demonstrated that PSO-BP neural network method is more suitable for homogenous and heterogeneous reservoir.©2018 Southwest Petroleum University.

Microstructure and Properties of In Situ Si and Fe-rich Particles Reinforced Al Matrix Composites Assisted with Ultrasonic Vibration

In this research, the in situ Si and Fe-rich particles reinforced Al matrix composites were fabricated by rheocasting(RC) process assisted with ultrasonic vibration(USV). After USV treatment, the polygonal primary Si crystals were refined into particles with average diameter of about 15–23 lm, and the fraction of primary Si declined to about5.4–6.5 vol%. The coarse plate-like d-Al4(Fe,Mn)Si2phase was transformed into fine particles with average diameter of about 17–20 lm, and the fraction of particle-like Fe-bearing particles is about 3.6–5.3 vol%. The ultimate tensile strength of the RC composites increases with the increase of Fe content at 350 °C. The increase of the elevated temperature strength of the composites is mainly attributed to the refinement of d-Al4(Fe,Mn)Si2phase and the increase of the volume fraction of the Fe-bearing compounds. Compared with the composites without USV, the RC composites assisted with USV have thinner mechanical mixing layer in wear test, which corresponds to smaller wear rate.

Polynomial synchronization of complexvalued inertial neural networks with multiproportional delays

This paper investigates the polynomial synchronization(PS)problem of complex-valued inertial neural networks with multi-proportional delays.It is analyzed based on the non-separation method.Firstly,an exponential transformation is applied and an appropriate controller is designed.Then,a new sufficient criterion for PS of the considered system is derived by the Lyapunov function approach and some inequalities techniques.In the end,a numerical example is given to illustrate the effectiveness of the obtained result.

Irrational-Behavior-Proof Conditions for Stochastic Games over Event Trees

In this paper,the irrational-behavior-proof conditions in a class of stochastic dynamic games over event trees are presented.Four kinds of irrational-behavior-proof conditions are proposed by the imputation distribution procedure,and their relationships are discussed.More specific properties for the general transformation of characteristic functions are developed,based on which,the irrational-behavior-proof conditions are proved to be true in a transformed cooperative game.