Research and Application of an Environmental-Friendly Low-Damage and High Salt-Resistance Slick Water Fracturing Fluid System

The Sulige gas field is a typical low-pressure low-permeability tight sandstone gas reservoir. The reservoir has poor seepage capacity, strong heterogeneity, high mineralization of formation water and extremely scarce water resources on the site. These unfavorable factors have brought great difficulties to the on-site mining process. Now, a nano-composite green environmental protection slick water fracturing fluid system CQFR can be quickly dissolved because of the larger specific surface area, and the small molecular size makes the damage to the reservoir less than 5%, and the average drag reduction effect can reach more than 73%. It can quickly and well dissolve and maintain performance under high salinity conditions and fracturing flowback fluids. It responds well to the complex reservoir conditions on the construction site and makes the flowback fluid recyable, which greatly reduces the consumption of water resources on the construction site and effectively improves the construction efficiency and economic benefits.

Hierarchical Magnetic Network Constructed by CoFe Nanoparticles Suspended Within “Tubes on Rods” Matrix Toward Enhanced Microwave Absorption

Hierarchical magnetic-dielectric composites are promising functional materials with prospective applications in microwave absorption(MA)field.Herein,a three-dimension hierarchical“nanotubes on microrods,”core–shell magnetic metal–carbon composite is rationally constructed for the first time via a fast metal–organic frameworksbased ligand exchange strategy followed by a carbonization treatment with melamine.Abundant magnetic CoFe nanoparticles are embedded within one-dimensional graphitized carbon/carbon nanotubes supported on micro-scale Mo2N rod(Mo2N@CoFe@C/CNT),constructing a special multi-dimension hierarchical MA material.Ligand exchange reaction is found to determine the formation of hierarchical magnetic-dielectric composite,which is assembled by dielectric Mo2N as core and spatially dispersed CoFe nanoparticles within C/CNTs as shell.Mo2N@CoFe@C/CNT composites exhibit superior MA performance with maximum reflection loss of−53.5 dB at 2 mm thickness and show a broad effective absorption bandwidth of 5.0 GHz.The Mo2N@CoFe@C/CNT composites hold the following advantages:(1)hierarchical core–shell structure offers plentiful of heterojunction interfaces and triggers interfacial polarization,(2)unique electronic migration/hop paths in the graphitized C/CNTs and Mo2N rod facilitate conductive loss,(3)highly dispersed magnetic CoFe nanoparticles within“tubes on rods”matrix build multi-scale magnetic coupling network and reinforce magnetic response capability,confirmed by the off-axis electron holography.

Timing of the formation of the Baiyinnuo'er skarn Zn–Pb deposit,NE China:evidence from sulfide Rb–Sr dating

The Baiyinnuo’er deposit in northern China is located in the south section of the Great Xing’an Range,and it is the largest skarn Zn–Pb deposit in the region.Skarn and Zn–Pb orebodies mainly occur between the different units of the Permian Huanggangliang Formation,or within the contact zone between the intrusive rocks and the marble.Although Baiyinnuo’er has been well investigated previously,the timing of the Zn–Pb mineralization is still controversial,largely due to the lack of appropriate ore or alteration minerals that could be directly used for isotopic dating.In this study,we report the results of Rb–Sr isotopic analysis for sphalerite and pyrite samples from the Baiyinnuo’er orebodies,which yielded two isochron ages of 137.4±3.4 and 140.0±7.8 Ma,respectively,constraining the Zn–Pb mineralization time of the deposit as the Early Cretaceous.The data are also consistent with the age of the granitoids in the mining area,indicating a potential genetic relationship between the Early Cretaceous magmatism and mineralization.Many other intrusion-related hydrothermal deposits(including the two typical skarns,Huanggang and Haobugao)in the southern Great Xing’an Range also share similar mineralization ages(i.e.,140–130 Ma).Together,these data suggest an Early Cretaceous mineralization event in this region,and this largescale mineralization could be related to the regional tectonic regime transition from compression to extension as a result of the rollback of the subducted Paleo-Pacific plate.The initial87 Sr/86 Sr ratios of the sphalerite and pyrite samples are 0.70569 and 0.70616,respectively,implying that the ore-forming material could have a significant contribution from the mantle components.The current study shows that sulfide Rb–Sr dating could be used in deciphering the timing of skarn deposit formation.

Growth of magnetic metals on carbon microspheres with synergetic dissipation abilities to broaden microwave absorption

Microwave absorption(MA) materials have been captured extensive attentions due to the serious electromagnetic(EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with magnetic constituents as cores and dielectric constituents as shells, which inevitably suppressed the magnetic coupling causing the decrease of magnetic loss to some extent. Herein, the coreshell structural carbon(C) microsphere/magnetic metal composites were fabricated through the combination of an electrostatic assembly approach and subsequent in-situ reduction reaction. The complex permittivity and permeability of core-shell C@magnetic metal composite system can be effective adjusted by the constituent and microstructure of shells. Thanks to the distinct magnetic coupling from the subtle designed structures and the promotion of the magnetic-dielectric synergy, the C@magnetic metal composite exhibited enhanced MA properties. The optimal reflection loss(RL) of C@Ni composite was-54.1 dB with a thickness of 3.4 mm, meanwhile the effective absorbing band could reach over 5.5 GHz at only a1.8 mm thickness. Broad absorption bandwidth with RL below-10 d B could achieve 6.0 GHz and 6.7 GHz for C@Co and C@Ni Co composites with a thin 2.1 mm thickness, respectively. Our exciting findings might lead a guide on the novel structure design for the functional core-shell structural composites used for microwave absorption.

Mineralogical Characteristics and in-situ Sulfur Isotopic Analysis of Gold-Bearing Sulfides from the Qilishan Gold Deposit in the Jiaodong Peninsula,China

Large-scale gold mineralization during the Early Cretaceous is identified in the Jiao-dong Peninsula of China.Sources of ore-forming fluids remain debated.We study the Qilishan gold deposit in the northwestern Jiaodong Peninsula with detailed mineralogical observation and in-situ sulfur isotope analyses,in order to reveal the gold occurrence and the origin of ore-forming fluids.The Qilishan gold deposit is mainly clastic altered rock-type in mineralization,and ore minerals are visible native gold,electrum,pyrite,chalcopyrite and galena,gangue minerals as quartz,sericite and calcite.The gold occurrence includes inclusion and intergranular types,formed within pyrites and chalcopy-rites and along their fissures.In-situ sulfur isotope analysis of gold-bearing sulfides suggests that the Qilishan deposit is enriched in heavy sulfur,withδ34S values mainly from+8.0‰to+12.0‰.δ34S val-ues increase gradually with the fluid evolution from the early to late stages,which is interpreted to be related to the loss of sulfur via sulfide precipitation.The crystallization of sulfides from hydrothermal fluids may have triggered the instability of Au(HS)2,and finally led to gold precipitation.Combined with sulfur isotope compositions of other gold deposits(n=43)and wall-rocks in the Jiaodong Peninsu-la,it is proposed that the ore-forming fluids were probably not directly originated from metamorphic wall-rocks(e.g.,Jiaodong Group).Moreover,the relatively long time interval rules out the possibility that the gold mineralization(ca.120 Ma)was associated with granitic magma activities(mostly 160-150 Ma).Possible ore genesis scenario is that,long-term subduction of slabs(e.g.,the Paleo-Pacific)with gold-enriched pyritic materials and crustal sedimentary rocks resulted in both high Au contents and positiveδ34S values of sulfur in the lithospheric mantle below the North China Craton.Subse-quently,devolatilization of the metasomatized mantle produced auriferous fluids that migrated up-ward along translithospheric fault systems,and gold finally precipitated in favorable structural posi-tions,generating the world-class Jiaodong deposits in the Early Cretaceous.

Enhanced magnetic properties and improved corrosion performance of nanocrystalline Pr-Nd-Y-Fe-B spark plasma sintered magnets

Recently it is a hot topic to make full use of high abundant Y element in Nd_(2)Fe_(14)B-type permanent magnets.In contrast to Pr and Nd elements,Y shows different metallurgical behaviors during preparation process.In this paper,we have explored the magnetic properties,microstructures and corrosion performance of Pr-Nd-Y-Fe-B magnets fabricated by spark plasma sintering(SPS)technique from the ribbons of nanocrystalline and amorphous precursors,respectively.The coercivity and maximum energy product were improved for the magnets prepared from amorphous precursor materials(denoted as SPS-A hereafter)compared with the magnets prepared from crystalline precursor materials(denoted as SPS-C hereafter).Magnetic properties of Jr=0.79 T,Hci=864 k A/m,and(BH)_(max)=102 k J/m^(3)were obtained for SPS-A magnets.In contrast with SPS-C magnets,the magnetic properties of SPS-A magnets are not so sensitive to the preparation conditions,which is quite beneficial to the homogeneity of microstructure and enhancement of coercivity for large-scale production of the designated magnets.Aggregated(Pr,Nd,Y)-rich phase was found out in SPS-C magnets.Pr and Nd elements are rich at grain boundary while Y is distributed uniformly at main phase and grain boundary phase.The strip grains and equiaxed grains exist in SPS-C and SPS-A magnets,respectively.The enhanced magnetic properties for SPS-A magnets are accredited to the uniform distribution of rare-earth-rich phase and low demagnetization factor.It is revealed by electrochemical test and dipping test that the corrosion potential is more positive and the corrosion rate is slower for the SPS-A magnets in 3.5 wt.%Na Cl solution.The work is also expected to shed light on developing the nanocrystalline Pr-Nd-Y-Fe-B SPSed high-performance magnets in industry.