Relationship Between Electrical Properties and Sedimentary Environment of the Longmaxi Formation Shale, Southern Sichuan     

YANG Kai  ZHANG Bing  WANG Xuben  HE Lanfang  YANG Hongyu  WANG Pengwan  TANG Jialin  DENG Jixin  ZHANG Cong 《《地质学报》英文版》2020,94(5):1531-1546

The Lower Silurian Longmaxi Formation in the south of Sichuan is a key player in the exploration and development of shale gas in China. Due to a highly complex topographic area, electromagnetic methods (EM) become important exploration means in this area. Many studies have been conducted on the shale mineral composition and electrical properties of shale, however, the correlation between sedimentary environments and the electrical properties of shale remain poorly understood. The electrical properties and sedimentary environment of the organic-rich shale of the Longmaxi Formation have been studied by means of X-ray diffraction, organic geochemistry, scanning electron microscopy and complex resistivity measurements. The discovered high quartz content of the Longmaxi Formation shale results in low resistivity. Deep-water shelf biogenic quartz contributes lower resistivity more than that of shallow-water terrigenous quartz. The deep-water anoxic and organic sedimentary environment led to major enrichment of pyrite, leading to a high polarization effect in shale. We present the correlation between the lithofacies types and electrical properties of Longmaxi Formation. The mixed siliceous shale lithofacies is the most favorable among the three lithofacies, which is characterized by high total organic carbon (TOC) content, high brittleness mineral content, high polarization and low resistivity (“three high and one low”). This feature is an effective identification of shale gas reservoirs by electromagnetic prospecting. Our study can provide constraints on electrical parameters of rocks for electromagnetic “sweet spot” exploration of shale gas, and so this has important geological significance to shale gas exploration and development.  相似文献   

断层附近地应力扰动带宽度及其影响因素   总被引：3，自引：3，他引：0  

翁剑桥  曾联波  吕文雅  刘奇  祖克威 《地质力学学报》2020,26(1):39-47

在建立正断层模型的基础上，利用三维有限元数值模拟方法研究了断层附近地层中的地应力变化规律。其结果表明，由于断层活动，在断层附近普遍发育应力扰动带；在应力扰动带范围内，地应力方向和大小发生明显的变化，断层中部附近应力值普遍较低，而断层端部的应力值通常异常增大。应力扰动带的分布范围主要受断层规模的控制，与断裂带的岩石力学性质、断层走向、断层面形态和边界应力条件等因素也密切相关。随断层长度和断距逐步增大，应力扰动带的宽度相应增加。断裂带的岩石越破碎，其岩石弹性模量越低，断层对地应力的影响宽度越大。断层走向与区域最大水平主应力方向越接近垂直、断距与断层长度的比值越大，区域内的差应力越大，则扰动带宽度与断层规模的比值也越大。选择渤海湾盆地BZ-X油田进行验证，在建立油田实际三维地质模型基础上，根据边界应力条件，利用三维有限元方法对沙河街组二段的地应力分布进行了数值模拟计算。根据断层周围的地应力变化，确定了应力扰动带的分布范围，断层附近应力扰动带宽度的分布规律与正断层模型分析结果相一致。   相似文献   

沉积物中硬质粘土层的研究进展          下载免费PDF全文

孔凡彪  徐树建  贾广菊 《山东国土资源》2018,34(3)

大量的钻孔资料表明,平原地区及其海域沉积物中普遍有硬质粘土层的存在。硬质粘土层在工程地质、地理学研究等方面具有重要的价值,它不仅是高层建筑的持力层,而且是研究全球环境变化事件、古气候演变的良好载体。该文阐述了硬质粘土层的一般特征、成因以及在粒度、地球化学元素、年代学、沉积环境等方面的研究进展,并展望了硬质粘土层在年代、物质来源和沉积环境等方面的研究方向,认为黄河三角洲硬质粘土层研究较少,需要开展大范围的、系统深入的、多学科的宏观和微观综合分析,挖掘硬质粘土层蕴含的古环境意义和应用价值。  相似文献   

基于"山西2015速度模型"的定位方法对比研究     

殷伟伟  宋秀青  李自红  朱元清 《大地测量与地球动力学》2018,38(5):469-472

为了确定山西台网基于“山西2015速度模型”的相对固定的定位方法，选择2010~2016年最大空隙角小于45°、参与定位台站数大于40的103个地震事件，分别采用单纯形法、Hypo2000、Hyposat结合PTD等3种方法重新测定。结果显示，单纯形法和Hyposat结合PTD测定的残差以及网缘地震的震中距两方面均优于Hypo2000；在震源深度方面，Hyposat结合PTD的结果较为可信。综合分析认为，基于“山西2015速度模型”定位地震时，山西台网应固定使用Hyposat结合PTD的方法。  相似文献   

Calibration method affects the measured δ2H and δ18O in soil water by direct H2Oliquid–H2Ovapour equilibration with laser spectroscopy     

Hongxiu Wang  Bingcheng Si  Dyan Pratt  Han Li  Xiaojun Ma 《水文研究》2020,34(2):506-516

The direct H₂O_liquid–H₂O_vapour equilibration method utilizing laser spectroscopy (DVE-LS) is a way to measure soil pore water stable isotopes. Various equilibration times and calibration methods have been used in DVE-LS. Yet little is known about their effects on the accuracy of the obtained isotope values. The objective of this study was to evaluate how equilibration time and calibration methods affect the accuracy of DVE-LS. We did both spiking and field soil experiments. For the spiking experiment, we applied DVE-LS to four soils of different textures, each of which was subjected to five water contents and six equilibration times. For the field soil experiment, we applied three calibration methods for DVE-LS to two field soil profiles, and the results were compared with cryogenic vacuum distillation (CVD)-LS. Results showed that DVE-LS demonstrated higher δ²H and δ¹⁸O as equilibration time increased, but 12 to 24 hr could be used as optimal equilibration time. For field soil samples, DVE-LS with liquid waters as standards led to significantly higher δ²H and δ¹⁸O than CVD-LS, with root mean square error (RMSE) of 8.06‰ for δ²H and 0.98‰ for δ¹⁸O. Calibration with soil texture reduced RMSE to 3.53‰ and 0.72‰ for δ²H and δ¹⁸O, respectively. Further, calibration with both soil texture and water content decreased RMSE to 3.10‰ for δ²H and 0.73‰ for δ¹⁸O. Our findings conclude that the calibration method applied may affect the measured soil water isotope values from DVE-LS.  相似文献   

Determination of Radiogenic 87Sr/86Sr and Stable δ88/86SrSRM987 Isotope Values of Thirteen Mineral,Vegetal and Animal Reference Materials by DS‐TIMS     

Jean‐Michel Brazier  Anne‐Dsire Schmitt  Eric Pelt  Damien Lemarchand  Sophie Gangloff  Tho Tacail  Vincent Balter 《Geostandards and Geoanalytical Research》2020,44(2):331-348

This work presents new ⁸⁷Sr/⁸⁶Sr and δ^88/86Sr_SRM987 isotopic values of thirteen mineral, vegetal and animal reference materials. Except for UB‐N, all our results are consistent with previously published data. Our results highlight intermediate precisions among the best presently published and a non‐significant systematic shift with the calculated δ^88/86Sr_SRM987 mean values for the three most analysed reference materials in the literature (i.e., IAPSO, BCR‐2 and JCp‐1). By comparison with the literature and between two distinct digestions, a significant bias of δ^88/86Sr_SRM987 values was highlighted for two reference materials (UB‐N and GS‐N). It has also been shown that digestion protocols (nitric and multi‐acid) have a moderate impact on the δ^88/86Sr_SRM987 isotopic values for the Jls‐1 reference materials suggesting that a nitric acid digestion of carbonate can be used without significant bias from partial digestion of non‐carbonate impurities. Different δ^88/86Sr_SRM987 values were measured after two independent Sr/matrix separations, according to the same protocol, for a fat‐rich organic reference material (BCR‐380R) and have been related to a potential post‐digestion heterogeneity. Finally, the δ^88/86Sr_SRM987 value differences measured between animal‐vegetal and between coral‐seawater reference materials agree with the previously published results, highlighting an Sr isotopic fractionation along the trophic chain and during carbonate precipitation.  相似文献   

Barium Isotopic Compositions in Thirty‐Four Geological Reference Materials Analysed by MC‐ICP‐MS     

Ya‐Jun An  Xin Li  Zhao‐Feng Zhang 《Geostandards and Geoanalytical Research》2020,44(1):183-199

Measurement of Ba isotope ratios of widely available reference materials is required for interlaboratory comparison of data. Here, we present new Ba isotope data for thirty‐four geological reference materials, including silicates, carbonates, river/marine sediments and soils. These reference materials (RMs) cover a wide range of compositions, with Ba mass fractions ranging from 6.4 to 1900 µg g^?1, SiO₂ from 0.62% to 90.36% m/m and MgO from 0.08% to 41.03% m/m. Accuracy and precision of our data were assessed by the analyses of duplicate samples and USGS rock RMs. Barium isotopic compositions for all RMs were in agreement with each other within uncertainty. The variation of δ^138/134Ba in these RMs was up to 0.7‰. The shale reference sample, affected by a high degree of chemical weathering, had the highest δ^138/134Ba (0.37 ± 0.03‰), while the stream sediment obtained from a tributary draining carbonate rocks was characterised by the lowest δ^138/134Ba (?0.30 ± 0.05‰). Geochemical RMs play a fundamental role in the high‐precision and accurate determination of Ba isotopic compositions for natural samples with similar matrices. Analyses of these RMs could provide universal comparability for Ba isotope data and enable assessment of accuracy for interlaboratory data.  相似文献   

Precise Determination of Astronomical Azimuth by the Hour Angle Method of Multiple Meridian Stars     

《Chinese Astronomy and Astrophysics》2020,44(4):536-548

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堆积阶地古老滑坡识别方法及其在线状工程地质勘察中的应用     

安玉科  樊江  马胜午  马建全  高娟  毛立军 《吉林大学学报(地球科学版)》2020,50(6):1787-1794

阶地型古老滑坡体形成后，长期受各种营力影响，导致古老滑坡地貌形态破坏严重甚至消失。目前遥感技术和普通工程地质调绘很难发现这些滑坡的存在，给工程建设和后期运营造成较大安全隐患。为准确识别形态特征不明显的古老滑坡体，从阶地物质结构特征演变入手，找到阶地受剪切破坏产生的典型物质结构特征，将地层结构错断、卵砾石异常定向排列、摩擦镜面和泥包粒的眼球构造等作为滑坡准确识别依据。首先采用沿沟谷进行工程地质测绘的纵横交错追踪法确定滑坡体纵向范围和滑面形状，再结合地貌特征推测各级、块滑坡平面范围和分布，最后用点状勘探工程验证和校正推测结论。可将其总结为由"地貌异常、沿沟追踪、面上推断、点状校验"组成的阶地型滑坡识别方法，即物质结构异常推断法。结合线状工程勘察设计各阶段工作特点，提出线状工程前期工作中阶地型滑坡识别步骤，并在临渭高速公路工程建设项目中取得成功应用。  相似文献   

格尔木河水质现状及生态风险评估          下载免费PDF全文

李雷明  武君  徐娟  温小虎  闵秀云  郭效瑛  柴小丽  李廷伟 《盐湖研究》2019,27(1):89-98

为了解经济迅速发展背景下格尔木河流域水体中痕量元素分布、水环境质量现状和生态风险,对格尔木河9个采样点水样21种痕量元素的分布及相关性进行了分析,以Cu、Zn、Hg、Cd、Cr和Pb为目标重金属,评估了格尔木河水质现状及生态风险。结果表明:重金属Pb浓度在所有水样中均低于检出限,其它痕量元素浓度在0.001(Cd)～6297.013(Sr)μg·L~(-1)范围变化。根据相关性分析,推测格尔木河水体中Li、Sc、Ti、V、Cu、Ge、Rb、Sr、Mo、Cd来源可能相同。采样点水样6种重金属浓度均达到地表水环境质量I类的标准。采用5种方法评价了格尔木河水质现状,研究区水质处于无污染的理想状态。格尔木河重金属引发的潜在生态风险处于低风险水平(生态风险指数变化范围为0.35～0.68)。  相似文献