Reverse Weathering in River-dominated Marginal Seas   总被引：1，自引：1，他引：0  

Bin Zhao  Peng Yao  Zuosheng Yang  Zhigang Yu 《地球科学进展》2018,33(1):42-51

In estuarine regions and marginal seas, reverse weathering refers to the formation of authigenic aluminosilicate and carbonate minerals promoted by large inputs of terrestrial weathering products and intense remineralization of Sedimentary Organic Carbon (SOC), which is opposite to land weathering process. Compared with the process in open ocean, the formation of authigenic aluminosilicate and carbonate minerals caused by reverse weathering in estuarine regions and marginal seas is rather rapid, playing an important role in the maintenance of ocean acidity and elements cycles. At present, there are two research methods regarding the reverse weathering process, i.e., direct observation and chemical detection. The first method is used to study the structure and chemical composition of authigenic minerals and the second is mainly used to do quantified studies of authigenic minerals. The reverse weathering is very important to the cycles of Si, C, major ions (F^-, Li⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺), and alkali metal cations (Fe, Mn and Al) in marine environments, which promotes the burial of these elements in marine sediments. Due to large inputs of weathering products rich in Fe, Mn and Al oxides, precipitation of labile OC and biogenic silica, intense remineralization process and suboxic/anoxic conditions, estuarine and marginal seas are suitable sites for reverse weathering studies. The reverse weathering studies in sub-tropical and temperate estuaries should be emphasized in the future.  相似文献   

气举反循环钻井技术在超深地热井钻探中的应用     

杨凤山 《城市地质》2012,(3):50-52

本文通过地热钻井气举反循环施工实例,说明其钻井深度可以达到4000m以下的深度。  相似文献   

基于Hilbert变换的全波场分离逆时偏移成像   总被引：2，自引：2，他引：0       下载免费PDF全文

王一博  郑忆康  薛清峰  常旭  Tong W. Fei  Yi Luo 《地球物理学报》2016,59(11):4200-4211

逆时偏移方法利用双程波算子模拟波场的正向和反向传播,通常采用互相关成像条件获得偏移剖面,是一种高精度的成像方法.但是传统的互相关成像条件会在偏移结果中产生低频噪声;此外,如果偏移速度中存在剧烈速度变化还可能进一步产生偏移假象.为了提高逆时偏移的成像质量,可在成像过程中先对震源波场和检波点波场分别进行波场分离,然后选择合适的波场成分进行互相关成像.本文基于Hilbert变换,推导了可在偏移过程中进行上下行和左右行波场分离的高效波场分离公式以及相应的成像条件,结合Sigsbee 2B合成数据,给出了不同波场成分的互相关成像结果.数值算例结果表明,采用本文提出的高效波场分离算法以及合理的波场成分互相关成像条件可以获得高信噪比的成像结果.  相似文献   

Compositions and constituents of freshwater dissolved organic matter isolated by reverse osmosis     

Yulong Zhang  Wen Huang  Yong Ran  Jingdong Mao 《Marine pollution bulletin》2014

Dissolved organic matter (DOM) from riverine and lacustrine water was isolated using a reverse osmosis (RO) system. Solid-state ¹³C nuclear magnetic resonance (¹³C NMR) was used to quantitatively evaluate the compositions and constituents of DOM, which are compared with previous investigations on marine DOM. Results indicated that concentration factor (CF) was a key metric controlling yield and sorption of DOM on the RO system. The sorption was likely non-selective, based on the ¹³C NMR and δ¹³C analyses. Carbohydrates and lipids accounted for 25.0–41.5% and 30.2–46.3% of the identifiable DOM, followed by proteins (18.2–19.8%) and lignin (7.17–12.8%). The freshwater DOM contained much higher alkyl and aromatic C but lower alkoxyl and carboxyl C than marine DOM. The structural difference was not completely accounted for by using structure of high molecular weight (HMW) DOM, suggesting a size change involved in transformations of DOM during the transport from rivers to oceans.  相似文献   

Bayesian estimation of inflow hydrographs in ungauged sites of multiple reach systems     

《Advances in water resources》2014

A Bayesian Geostatistical Approach to evaluate unknown upstream flow hydrographs in multiple reach systems is implemented. The methodology was, firstly, tested through three synthetic examples of river confluences, that differ in the available data, boundary conditions and number of the estimated inflow time series. Input discharge hydrographs were routed downstream by means of the widely known HEC-RAS river analysis system to obtain the downstream stage hydrographs used as known observations for the reverse procedure. In almost all cases, the observed water levels were corrupted with random errors to highlight the reliability of the methodology in preventing instabilities and overfitting. Then the procedure was applied to the real case study of the Parma–Baganza river confluence located at the city of Parma (Italy) to assess the tributary Baganza River inflow hydrograph (supposed completely ungauged) using water level data collected downstream on the main reach. The results show that the methodology properly reproduces the unknown inflows even in presence of errors affecting the downstream water levels. The practical applicability of the proposed approach is also demonstrated in complex river systems.  相似文献   

Centrifuge modeling of interaction between reverse faulting and tunnel     

《Soil Dynamics and Earthquake Engineering》2014

In this study, a series of centrifuge tests, modeling reverse fault rupture with 60° dip angle, were conducted in a dry sandy soil with a tunnel embedded in the soil layer. The test results showed that the tunnel and soil responses depended on the tunnel position, soil relative density and tunnel rigidity. Tunnels appeared be able to deviate the fault rupture path, while this deviation may be associated with significant rotation and displacement of the tunnel. However, a deeper tunnel was able to diffuse the shear deformation to a wider zone with an unsmooth surface displacement which may cause severe damage to the surface structures. Finally, the tunnel rotation, the location of the fault outcropping, the vertical displacement of the ground surface, the effect of tunnel rigidity on fault rupture path and surface displacement and the effect of soil relative density on fault–tunnel interaction were reported and discussed in this study.  相似文献   

逆断层中天然气运移特征的物理模拟   总被引：11，自引：5，他引：6  

吕延防  孙永河  付晓飞  付广  杨勉  祝彦贺 《地质科学》2005,40(4):464-475

逆断层在活动期时易形成断层空腔,该空腔为天然气的穿层运移提供了畅通的通道,天然气在其中运移具涌流特征。如果断层空腔连通地表,天然气则大部分沿其逸出地表,仅有少量的天然气能注入断层两侧的相邻储层中。进入储层的天然气具有明显的选择性,气体首先向物性好、倾角陡和埋藏浅的储层中注入。如果没有其它动力,仅靠天然气自身浮力作用,断层下盘储层不能或很少能有天然气的注入。当断层处于静止期时,断层空腔消亡,天然气穿塑性层段的运移通道是破碎带中的岩石孔隙,天然气在其中的运移遵循达西渗流规律。天然气在断层带中的运移速度随断层充填物颗粒粒度的增加而呈指数关系增大,随断层倾角的增大呈指数关系增大,随断层充填物中泥质含量的增加呈幂函数关系减小。  相似文献   

The distinctive compositional evolution of glauconite in the Cretaceous Ukra Hill Member (Kutch basin,India) and its implications     

《Marine and Petroleum Geology》2017

An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al^3+-Fe³⁺ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K₂O as well as Fe₂O₃ contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of glauconite in a high a_Si+ and high a_K+ pore water environment. Incipiently formed glauconite records a marginal increase in K₂O content accompanied by release of Al₂O₃ and SiO₂ to form evolved glauconite pellets; those forming within quartz grains involve an addition of Fe₂O₃ (total) content during maturation. The minimal increase in K₂O content of incipiently formed glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K₂O and Fe₂O₃ (total) content of glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.  相似文献   

基于全波形反演的探地雷达数据逆时偏移成像   总被引：1，自引：1，他引：0       下载免费PDF全文

雷林林  刘四新  傅磊  吴俊军 《地球物理学报》2015,58(9):3346-3355

逆时偏移成像(RTM)常用来处理复杂速度模型,包括陡倾角及横向速度变化剧烈的模型.与常规偏移成像方法(如Kirchhoff偏移)相比,逆时偏移成像能提供更好的偏移成像结果,近些年逆时偏移成像越来越广泛地应用到勘探地震中,它逐渐成为石油地震勘探中的一种行业标准.电磁波和弹性波在动力学和运动学上存在相似性,故本文开发了基于麦克斯韦方程组的电磁波逆时偏移成像算法,并将其应用到探地雷达数据处理中.时间域有限差分(FDTD)用于模拟电磁波正向和逆向传播过程,互相关成像条件用于获得最终偏移结果.逆时偏移成像算法中,偏移成像结果受初始模型影响较大,而其中决定电磁波传播速度的介电常数的影响尤为重要.本文基于时间域全波形反演(FWI)算法反演获得了更为精确的地下介电常数模型,并将其反演结果作为逆时偏移成像的初始介电常数模型.为了验证此算法的有效性,首先构建了一个复杂地质结构模型,合成了共偏移距及共炮点探地雷达数据,分别应用常规Kirchhoff偏移算法及逆时偏移成像算法进行偏移处理,成像结果显示由逆时偏移成像算法得到的偏移结果与实际模型具有较高的一致性;此外本文在室内沙槽中进行了相关的物理模拟实验,采集了共偏移距及共炮点探地雷达数据,分别应用Kirchhoff和叠前逆时偏移成像算法进行处理,结果表明叠前逆时偏移成像在实际应用中能获得更好的成像效果.  相似文献   

地震叠前逆时偏移高阶有限差分算法及GPU实现   总被引：21，自引：10，他引：11       下载免费PDF全文

刘红伟  李博  刘洪  佟小龙  刘钦 《地球物理学报》2010,53(7):1725-1733

叠前逆时偏移技术是解决地震成像问题的有力工具,但由于计算量大、成像噪音以及存储量大等原因没有得到广泛的应用.本文给出了逆时偏移的实现过程,分析了高阶有限差分格式的稳定性与频散关系.针对叠前逆时偏移计算量大的问题,使用图形处理器(Graphic Processing Unit,简称GPU)实现算法加速,比传统的CPU计算速度提高了一个数量级.文中对理论模型进行了计算,并与单程波偏移方法做比较,结果表明:叠前逆时偏移有效突破了成像倾角限制,对垂直断层、盐丘空腔内幕等特殊构造成像效果均有显著提高.本文尚未涉及成像噪音去除以及存储量等问题,笔者将另文阐述.  相似文献