Experimental investigation of carbon dioxide trapping due to capillary retention in saline aquifers

Capillary trapping is a physical mechanism by which carbon dioxide (CO₂) is naturally immobilized in the pore spaces of aquifer rocks during geologic carbon sequestration operations, and thus a key aspect of estimating geologic storage potential. Here, we studied capillary trapping of supercritical carbon dioxide (scCO₂), and the effect of initial scCO₂ saturation and flow rate on the storage/trapping potential of Berea sandstone. We performed two‐phase, scCO₂‐brine displacements in two samples, each subject to four sequential drainage–imbibition core‐flooding cycles to quantify end‐point saturations of scCO₂ with the aid of micro‐ and macro‐computed tomography imaging. From these experiments, we found that between 51% and 75% of the initial CO₂ injected can be left behind after the brine injection. We also observed that the initial scCO₂ saturation influenced the residual scCO₂ saturation to a greater extent than the rate of brine injection under the experimental conditions examined. In spite of differences in the experimental conditions tested, as well as those reported in the literature, initial and residual saturations were found to follow a consistent relationship.     

Updating Numerical Models of Masonry Arch Bridges by Operational Modal Analysis

This article aims at presenting and discussing the strategies for updating the finite element numerical modeling of stone masonry arch bridges using operational modal analysis. The study comprehended three bridges: two old ones, the St. Lázaro and the Lagoncinha bridges, and a recently constructed bridge in Vila Fria, Portugal. Updating of the bridge models is performed by comparing the numerical and experimental modal parameters. Three-dimensional detailed numerical models are used to perform modal analysis of the bridges. Experimental modal identification of the bridges is based on the measurement of their acceleration responses during normal operation. The assigned material properties are also based on available results obtained from in situ and laboratory tests and on the results of visual inspection and historical research carried out for both old bridges.     

Fluid mixing induced by hydrothermal activity in the ordovician carbonates in Tarim Basin,China

Permian hydrothermal activity in the Tarim Basin may have been responsible for the invasion of hot brines into Ordovician carbonate reservoirs. Studies have been undertaken to explain the origin and geochemical characteristics of the diagenetic fluid present during this hydrothermal event although there is no consensus on it. We present a genetic model resulting from the study of δ¹³C, δ¹⁸O, δ³⁴S, and ⁸⁷Sr/⁸⁶Sr isotope values and fluid inclusions (FIs) from fracture‐ and vug‐filling calcite, saddle dolomite, fluorite, barite, quartz, and anhydrite from Ordovician outcrops in northwest (NW) Tarim Basin and subsurface cores in Central Tarim Basin. The presence of hydrothermal fluid was confirmed by minerals with fluid inclusion homogenization temperatures being >10°C higher than the paleo‐formation burial temperatures both in the NW Tarim and in the Central Tarim areas. The mixing of hot (>200°C), high‐salinity (>24 wt% NaCl), ⁸⁷Sr‐rich (up to 0.7104) hydrothermal fluid with cool (60–100°C), low‐salinity (0 to 3.5 wt% NaCl), also ⁸⁷Sr‐rich (up to 0.7010) meteoric water in the Ordovician unit was supported by the salinity of fluid inclusions, and δ¹³C, δ¹⁸O, and ⁸⁷Sr/⁸⁶Sr isotopic values of the diagenetic minerals. Up‐migrated hydrothermal fluids from the deeper Cambrian strata may have contributed to the hot brine with high sulfate concentrations which promoted thermochemical sulfate reduction (TSR) in the Ordovician, resulting in the formation of ¹²C‐rich (δ¹³C as low as ?13.8‰) calcite and ³⁴S‐rich (δ³⁴S values from 21.4‰ to 29.7‰) H₂S, pyrite, and elemental sulfur. Hydrothermal fluid mixing with fresh water in Ordovician strata in Tarim Basin was facilitated by deep‐seated faults and up‐reaching faults due to the pervasive Permian magmatic activity. Collectively, fluid mixing, hydrothermal dolomitization, TSR, and faulting may have locally dissolved the host carbonates and increased the reservoir porosity and permeability, which has significant implications for hydrocarbon exploration.     

Food for all: An agent-based model to explore the emergence and implications of cooperation for food storage

Abstract

A consistent access to food is paramount for humans at individual and group level. Besides providing the basic nutritional needs, access to food defines social structures and has stimulated innovation in food procurement, processing and storage. We focus on the social aspects of food storage, namely the role of cooperation for the emergence and maintenance of common stocks. Cooperative food stocks are examined here as a type of common-pool resource, where appropriators must cooperate to avoid shortage (i.e. the tragedy of commons). ‘Food for all’ is an agent-based model in which agents face the social dilemma of whether or not to store in a cooperative stock, adapting their strategies through a simple reinforcement learning mechanism. The model provides insights on the evolution of cooperation in terms of storage efficiency and considering the presence of social norms that regulate reciprocity. For cooperative food storage to emerge and be maintained, a significant dependency on the stored food and some degree of external pressure are needed. In fact, cooperative food storage emerges as the best performing strategy when facing environmental stress. Likewise, an intermediate control over reciprocity favours cooperation for food storage, suggesting that concepts of closed reciprocity are precursors to cooperative stocks, while excess control over reciprocity is detrimental for such institution.     

博罗横岭山先秦墓地出土春秋青铜矛腐蚀情况研究

作为2000年全国十大考古发现之一,惠州市博罗横岭山先秦墓地出土了大量精美的青铜器、陶瓷器和玉石器。本文采用显微镜、X射线探伤、X射线荧光能谱、X射线衍射、显微拉曼等方法对其中一件春秋时期青铜矛进行综合分析。结果表明,该青铜矛为铜锡二元合金。受酸性潮湿的埋藏土壤环境影响,青铜矛基体矿化严重,表面存在大量以SnO₂为主要成分的浅绿色锈蚀物和少量以碱式碳酸铜为主要成分的绿色锈蚀物。X射线探伤分析显示,青铜矛内部存在泥芯铸造产生的空腔和多处小孔状铸造缺陷。此外,青铜矛表面大部分区域覆盖有结晶态的以SnO₂为主要成分的致密半透明锈蚀层,这在同类型的锈蚀青铜器中较为少见,是其出土之后能长年保持稳定的表面锈蚀状态且器形较为完整稳固的原因。实验结果可为该青铜矛的保护修复处理提供有力的理论依据和数据支持,并为研究南方地区同类型青铜器锈蚀产物提供参考。     

元刘天与墓志及相关问题探析

元《刘天与墓志》2009年采集于西安市长安区韦曲街办夏殿村之西,志主系蒙元时期著名的汉人世侯刘黑马家族后裔。该墓志内容丰富,尤其是涉及刘天与的仕宦经历及家族婚姻等内容为进一步研究"天成刘氏"家族史提供了新资料。     

广西革新桥遗址出土的石拍研究

革新桥遗址是一处新石器时代石器制造场遗址。2002年10月至2003年1月发掘,出土数以万计的石制品,还发现两座墓葬。年代为距今6000-5500年前。本文对该遗址中出土的一件石拍进行观察,并就其制作工艺及功能和用途进行探讨。     

试论《武王践祚》的文本流变

《上海博物馆藏战国楚竹书》(七)所收《武王践祚》,实为两种战国"简本"(甲本和乙本)的合抄。传世本则是参考了这两种简本,合编整理而成。与甲本相比,乙本在叙事及文字上更接近于原始的记录,成文应早于甲本。但甲本与乙本之间并没有直接的文本传承关系,应是两系文本发展的不同形态。参照乙本,可以推测《武王践祚》的原初结构,并不包括武王勒铭段。从文献体裁及文章内容看,甲本及传世本的这一段文字,应是合编自其他文献。《武王践祚》三个本子的比较研究显示,早期文献在流传过程中,不仅存在着文字的增饰、丢失与改动等现象,同时还存在着同种文献不同形态的合编整理甚至是不同文献的合并现象。这对我们认识早期文献形成及流传的特殊性,并进而讨论早期文献的史料价值,无疑具有重要的参考意义。     

动物考古学与复杂社会——动物群分析在贸易、社会地位和族属研究中的某些应用

自20世纪60年代后期以来,动物考古学成为考古学研究中发展最为迅速的分支学科之一,利用动物骨骼遗存研究复杂社会显示出动物考古学的特殊魅力。本文利用旧大陆西部和新大陆的动物考古学研究案例,首先讨论了动物和动物产品在贸易和交换中的作用,接下来又探讨了动物遗存的差异在多大程度上可以用来重建社会不平等,最后,则批判地考察了动物遗存在辨认史前和历史时代早期族群差异方面的作用。不仅如此,作者还讨论了从事复杂社会研究的动物考古学家所使用的方法,以及这些方法的局限性。作者认为,动物群分析可以作为研究复杂社会经济基础的一个有效方法。动物考古学除了为饮食和生存活动提供有价值的信息之外,动物骨骼分析还可以用于重建过去的交换系统,辨识人们的社会地位和族属。但要做到这一点,动物考古学家必须把分析建立在大量精心收集且出自合适的考古学遗迹单位的动物遗存之上。这意味着动物考古学家必须首先是考古学家,他们应当少花一些时间担心最小个体数、可鉴定标本数以及其他计算生物分类单元丰度的方式的优劣上,而应把更多的时间放在考虑怎样能把动物资料与其他考古学和历史学证据整合起来。因为只有把动物群资料和其他证据结合起来,我们才能理解复杂社会的经济基础。