Nanoscale pore morphology and distribution of lacustrine shale reservoirs:Examples from the Upper Triassic Yanchang Formation,Ordos Basin

Pore structure plays an important role in the gas storage and flow capacity of shale gas reservoirs. Fieldemission environmental scanning electron microscopy（FE-SEM） in combination with low-pressure carbon dioxide gas adsorption（CO2GA）,nitrogen gas adsorption（N2GA）,and high-pressure mercury intrusion（HPMI） were used to study the nanostructure pore morphology and pore-size distributions（PSDs） of lacustrine shale from the Upper Triassic Yanchang Formation,Ordos Basin. Results show that the pores in the shale reservoirs are generally nanoscale and can be classified into four types： organic,interparticle,intraparticle,and microfracture. The interparticle pores between clay particles and organic-matter pores develop most often,l with pore sizes that vary from several to more than 100 nm. Mercury porosimetry analysis shows total porosities ranging between 1.93 and 7.68%,with a mean value of 5.27%. The BET surface areas as determined by N2 adsorption in the nine samples range from 10 to 20 m2/g and the CO2 equivalent surface areas（2 nm）vary from 18 to 71 m2/g. Together,the HPMI,N2 GA,and CO2 GA curves indicate that the pore volumes are mainly due to pores 100 nm in size. In contrast,however,most of the specific surface areas are provided by the micropores. The total organic carbon（TOC） and clay minerals are the primary controls of the structures of nanoscale pores（especially micropores and mesopores）. Micropores are predominantly determined by the content of the TOC,and mesopores are possibly related to the content of clay minerals,particularly the illite-montmorillonite mixed-layer content.

Prospect Conceiving of Joint Research and Development of Shale Gas and Coalbed Methane in China

Inspired by successful development of shale gas in USA and influenced by hydrocarbon resources shortage currently, China has strengthened shale gas research and accelerated its exploration process. In order to enrich coalbed methane (CBM) and shale gas geological theory and promote their development process, this paper compared shale gas with CBM in accumulation, distribution, reservoir and production. It expatiated on the background and significance of the combined research and development, and analyzed the geological foundation and future prospects. Our investigation demonstrated that there are many sets of coal-bearing strata in Shanxi formation of Permian system in Ordos in North China, Longtan formation of Upper Permian and Xujiahe formation of Upper Triassic in Southern Yangtze region, Xishanyao formation of Middle Jurassic in Turpan-Hami Basin and Junggar Basin in Northwest China, and Shahezi formation of Cretaceous in Songliao Basin in northeast China. In these regions, shales which are interbeded with coal seams have the characters of big thickness, continuous distribution, high content of organic matter, good parent material and high maturity, accord with the basic geological conditions to format shale gas and CBM reservoir and composite gas reservoir, thus form appropriate regions and layers to carry out joint research and exploration with good prospects for development.

Influence of liquid water on coalbed methane adsorption:An experimental research on coal reservoirs in the south of Qinshui Basin

Using Isothermal Adsorption/Desorption System Model IS-100 and Electrohydraulic Servo Rock System Model MTS815 as the main apparatuses and collecting samples from the major coal reservoirs in the south of Qinshui Basin, a hot point region of coalbed methane exploration, the paper carries out systematical comparisons of the isothermal adsorption experimental data for injection water coal samples, equilibrium moisture samples and dry coal samples, probes and establishes an experimental method of injection water coal sample preparation and isothermal experiment to simulate real reservoir conditions, and then summaries the experimental regulations and discusses the mechanism of liquid water influencing coal methane adsorption. Results of the experiment indicate that: The Langmuir volume of injection water coal samples is notably larger than that of equilibrium moisture samples, as well as larger than or equivalent to that of dry coal samples; the Langmuir pressure of injection water coal samples is the highest, the next is equilibrium moisture samples, while the dry samples is the lowest, of which the experimental results of injection water samples to simulate real reservoir conditions are more close to the fact. Under the conditions of in-position reservoirs, liquid water in coals has evident influence on methane adsorption ability of coal matrix, which can increase the adsorbability of coal and make the adsorption regulation fit to Langmuir model better. Its major reason is the increase of wetting coal matrix adsorbability. The above experimental results overthrow the conventional cognition that liquid water has no influence on coalbed methane adsorption, which may lead to an improvement of the coalbed methane isothermal adsorption experimental method and of the reliability of coalbed methane resource evaluation and prediction.

以晶格匹配策略设计的超宽禁带(6.14 eV)(AlGa))_(2)O_(3)/Ga_(2)O_(3)异质结用于高灵敏度真空紫外探测

本文展示了一种利用超薄导电的Ga_(2)O_(3):Si纳米层获得(AlGa)_(2)O_(3)结晶薄膜的设计策略.受益于Ga_(2)O_(3):Si插层的存在,高质量的(Al_(0.68)Ga_(0.32))_(2)O_(3)倍半氧化物薄膜得以在蓝宝石衬底上外延生长,其中铝组分含量高达~68%,并被多种技术如HRTEM,XPS和XRD等进行了系统性表征.(Al_(0.68)Ga_(0.32))_(2)O_(3)材料的带隙被成功拓宽至6.14 eV,我们在此基础上制备出了(AlGa)_(2)O_(3)/Ga_(2)O_(3):Si真空紫外光电探测器.该探测器性能优异,开关比高达10^(3),开路电压为1.0 V,0 V偏压下响应度为8.1 m A W-1.以上结果表明,本文提出的生长策略可有效提高(AlGa)_(2)O_(3)倍半氧化物的质量并调节其带隙,有助于推动其在真空紫外探测领域的实际应用.

Raman spectroscopy regulation in van der Waals crystals

Raman spectroscopy is a versatile tool widely used for comprehensive probing of crystal information. However,generally when applied in narrow-band-gap van der Waals crystals, it is liable to form a "bug," especially in transition-metal-dichalcogenides(TMDs). That is, several resonant Raman-scattering(RS) modes will inevitably appear in the Raman spectra with strong intensity, interfering with the desired signal of optical-phonon modes.Here, we propose cross-sectional polarized Raman scattering capable of regulating the intensity of RS modes in accordance with quasi-sinusoidal rules. Typically, for MoS_2 and WS_2, when the polarization vector of excited light is along the c axis of the crystal, all RS modes are nearly completely "expunged" from the Raman spectra. The mechanism is that the absorption of most TMDs with a space group of R_(3m)for the light polarized along the c axis is infinitesimal, thus forming a small coupling intensity of electronic states excited optically and acoustic-phonon modes at point M, which in turn restrain the appearance of RS modes. The regulating strategy proposed can be applied to other van der Waals crystals so as to obtain a high signal-to-noise ratio Raman spectrum.

石墨的拉曼张量:G、D和D′声子的对称性

自石墨的拉曼光谱在1970年被首次记录以来,其拉曼特征峰(G、D和D′峰)背后的物理起源一直是人们争论的焦点.目前,人们普遍认为G峰对应于拉曼活性E_(2g2)模式,D和D′峰则是与缺陷有关的无序诱发峰.然而,到目前为止,这些石墨拉曼峰所对应的声子对称性,还缺乏细致的研究与直接的实验证据.在这里,我们利用角分辨偏振拉曼光谱对这些重要方面进行了阐述.结果表明,D、D′峰的实验拉曼强度与G峰的偏振角关系相似.结合拉曼张量分析和双共振机制,我们进一步了解了D′和D峰的声子对称性.我们的工作为石墨声子对称性提供了可靠的实验证据和合理的解释.

AlN的近真空紫外非周期振荡发射

近带边折射率的准确测量对于深紫外发光二极管和激光二极管的光学结构设计是非常重要的.通常,各向异性光学薄膜的折射率等光学常数可以通过变角度椭圆光谱仪测得.然而,这种方法仍存在一些局限性.本文提出了一种利用测量宽带半导体带边折射率色散的有潜力方法,在1500 nm厚的AlN薄膜的荧光光谱中观察到一种源于Fabry-Perot效应的非周期振荡发射现象.基于荧光光谱的特点以及Fabry-Perot效应的定义, AlN薄膜在干涉加强和减弱处对应波长的近带边o光折射率可以被直接获得.这种折射率测量方法对于变角度椭圆光谱法是一种补充,对于转移薄膜以及较薄样品,测量其荧光光谱是一种更为直接而且有效的方法.

AlN单晶中的激光调谐

激光波长调谐对于在压力检测、强电场监测、痕量气体探测以及可见光通讯领域中提高动态波长分配效率起着重要作用.拉曼散射是一种具有频移特性的非线性光学效应,这表明拉曼散射可能是一种实现激光波长调谐的可行方法.在本文中,我们发现在特定的测试结构下,氮化铝的A1(TO)模式对应的散射光具有线偏振特性.此外,通过温度调制,我们在氮化铝中实现了高精度的散射光波长调谐.基于实验结果,具有高热导率和高稳定性的氮化铝可能是一种实现激光波长调谐的良好载体.

层状WS2的拉曼张量

为完善范德瓦尔斯层状材料有关于拉曼张量的基本信息,本文采用角分辨偏振拉曼光谱对二硫化钨的拉曼张量进行研究.根据拉曼选择定则,我们分析了角分辨拉曼光谱与偏振的依赖关系,并结合实验结果获得了面内和面外各振动模式的拉曼张量元和与张量元对应的微分极化率等信息.实验结果表明,截面测试得到的拉曼强度具有偏振依赖性,其中沿c轴振动的A1g模式引起的微分极化率明显大于E1g和E2g模式,并且A1g模式自身在沿c轴的极化率也较沿a轴或b轴的大.这种通过角分辨偏振拉曼光谱研究拉曼张量的方法对其他范德瓦尔斯层状材料具有普遍性.

Pore structure complexity and its significance to the petrophysical properties of coal measure gas reservoirs in Qinshui Basin,China

The pore structure of continuous unconven-tional reservoirs(CURs)in coal measures was investigated using different technologies for 29 samples(9 coal samples,9 shale samples,and 11 sandstone samples)from Qinshui Basin,China.Results show that coals have relatively high porosities and permeabilities ranging from 4.02%to 5.19%and 0.001 to 0.042 mD,respectively.Micropores(<2 nm)are well-developed in coals and contribute to the majority of pore volume(PV)and specific surface area(SSA).The porosities and permeabilities are between 1.19%-4.11%,and 0.0001-0.004 mD of sand-stones with a predominance of macropores(>50 nm).However,shales are characterized by poorly petrophysical properties with low porosity and permeability.Macropores and mesopores(2-50 nm)are well-developed in shales compared with micropores.For coals,abundant organic matters are expected to promote the development of micropores,and clay minerals significantly control the performance of mesopores.For shales and sandstones,micropores are mainly observed in organic matters,whereas clay minerals are the important contributor to mesopores.Moreover,micropore SSA significantly deter-mines the adsorption capacity of CURs and sandstones have the best pore connectivity.The permeability of CURs is positively associated with the macropore PV since macropores serve as the main flow paths for gas seepage.Additionally,we also proposed that effective porosity has a significant effect on the permeability of CURs.The findings of this study could enhance the understanding of the multiscale pore structure of CURs and provide insights into the mechanisms that control gas storage,transport,and subsequent co-production for continuous unconventional natural gas(CUNG)in the Qinshui Basin and other coal-bearing basins worldwide.