Equations of state for basin geofluids: algorithm review and intercomparison for brines

Physical properties of formation waters in sedimentary basins can vary by more than 25% for density and by one order of magnitude for viscosity. Density differences may enhance or retard flow driven by other mechanisms and can initiate buoyancy‐driven flow. For a given driving force, the flow rate and injectivity depend on viscosity and permeability. Thus, variations in the density and viscosity of formation waters may have or had a significant effect on the flow pattern in a sedimentary basin, with consequences for various basin processes. Therefore, it is critical to correctly estimate water properties at formation conditions for proper representation and interpretation of present flow systems, and for numerical simulations of basin evolution, hydrocarbon migration, ore genesis, and fate of injected fluids in sedimentary basins. Algorithms published over the years to calculate water density and viscosity as a function of temperature, pressure and salinity are based on empirical fitting of laboratory‐measured properties of predominantly NaCl solutions, but also field brines. A review and comparison of various algorithms are presented here, both in terms of applicability range and estimates of density and viscosity. The paucity of measured formation‐water properties at in situ conditions hinders a definitive conclusion regarding the validity of any of these algorithms. However, the comparison indicates the versatility of the various algorithms in various ranges of conditions found in sedimentary basins. The applicability of these algorithms to the density of formation waters in the Alberta Basin is also examined using a high‐quality database of 4854 water analyses. Consideration is also given to the percentage of cations that are heavier than Na in the waters.     

Survey and excavation of the main well in Cape Town Castle, South Africa: fieldwork and structural aspects

During the last few decades, Cape Town Castle has been extensively renovated. Parallel to this, a series of archaeological excavations were undertaken under the auspices of different institutions. During the course of these, it became clear that one specific site needed to be approached in a rather unorthodox way. This site, the main well situated in the centre of the previous headquarters of the Dutch East India Company at the Cape of Good Hope, was filled with water. Owing to its inaccessibility and other constraints, which made the application of adapted excavation techniques necessary, the need arose to call in the assistance of a diver-archaeologist. This article describes the approach to fieldwork undertaken in the Kat well during 1989 and 1999 and some of this feature's structural details.     

Chloride ion concentrations during the compression of rocks to extract pore water

Pore water needs to be extracted from rocks with low permeabilities to allow the major ion concentrations in the pore water to be estimated. Compressing a rock is the most widely used method of extracting the pore water. However, ion concentrations have been found to change during compression in previous studies, and the mechanisms involved in such ion concentration changes have not yet been fully assessed. In this study, two natural rocks and four artificially prepared samples were compressed, and changes in the chloride ion (Cl^?) concentrations as the compression pressure increased were investigated. Mechanisms that could have caused the changes observed were then assessed. The Cl^? concentrations in squeezed water decreased as the pressure increased if the sample contained a significant amount of smectite. The strong dependence of Cl^? concentration on the amount of smectite indicated that smectite played an important role in decreasing the Cl^? concentration. The dilution of the pore water with interlayer water from the smectite appeared to be the dominant mechanism involved in the decrease in Cl^? concentration found in a Kunigel‐V1 sample, because dilution of the pore water with interlayer water quantitatively explained the decrease in the Cl^? concentration. The filter effect caused by the anion exclusion effect did not appear to be a dominant mechanisms in our case. However, Cl^? concentration decrease found in natural rocks could not be fully explained by dilution with interlayer water, so other mechanisms must be involved the phenomenon in natural rocks.     

Hydrogeology of the Krafla geothermal system,northeast Iceland

The Krafla geothermal system is located in Iceland's northeastern neovolcanic zone, within the Krafla central volcanic complex. Geothermal fluids are superheated steam closest to the magma heat source, two‐phase at higher depths, and sub‐boiling at the shallowest depths. Hydrogen isotope ratios of geothermal fluids range from ?87‰, equivalent to local meteoric water, to ?94‰. These fluids are enriched in ¹⁸O relative to the global meteoric line by +0.5–3.2‰. Calculated vapor fractions of the fluids are 0.0–0.5 wt% (~0–16% by volume) in the northwestern portion of the geothermal system and increase towards the southeast, up to 5.4 wt% (~57% by volume). Hydrothermal epidote sampled from 900 to 2500 m depth has δD values from ?127 to ?108‰, and δ¹⁸O from ?13.0 to ?9.6‰. Fluids in equilibrium with epidote have isotope compositions similar to those calculated for the vapor phase of two‐phase aquifer fluids. We interpret the large range in δD_EPIDOTE and δ¹⁸O_EPIDOTE across the system and within individual wells (up to 7‰ and 3.3‰, respectively) to result from variable mixing of shallow sub‐boiling groundwater with condensates of vapor rising from a deeper two‐phase reservoir. The data suggest that meteoric waters derived from a single source in the northwest are separated into the shallow sub‐boiling reservoir, and deeper two‐phase reservoir. Interaction between these reservoirs occurs by channelized vertical flow of vapor along fractures, and input of magmatic volatiles further alters fluid chemistry in some wells. Isotopic compositions of hydrothermal epidote reflect local equilibrium with fluids formed by mixtures of shallow water, deep vapor condensates, and magmatic volatiles, whose ionic strength is subsequently derived from dissolution of basalt host rock. This study illustrates the benefits of combining phase segregation effects in two‐phase systems during analysis of wellhead fluid data with stable isotope values of hydrous alteration minerals when evaluating the complex hydrogeology of volcano‐hosted geothermal systems.     

The Chun Doo-Hwan Authoritarian Regime’s Securitisation of Water: The Case of the Peace Dam,South Korea

This article explores the securitisation of water aimed at avoiding a political crisis for the Chun Doo-Hwan regime in South Korea (1979–1988) using the case of the Peace Dam. The legitimacy of the Chun regime was vulnerable because of diverse factors such as internal and external crises inherited from the previous regime and Chun’s rise to power through a military coup and civilian massacres. In this political situation, the securitisation of nature could be an effective method of curbing potential resistance and ruling a people facing a complex crisis. The constructed threat of an attack by flooding by North Korea and the consequent alleged need for the Peace Dam were part of a scheme by Chun to maintain political power through the securitisation of water, specifically by establishing North Korea as an external enemy and unifying the South Korean people.     

朵云轩木版水印与《十竹斋书画谱》的重梓

朵云轩传统的木版水印工艺精湛绝伦,复制艺术的水平达到了形神兼备以至乱真的境地。木版水印工艺重梓精印《十竹斋画谱》并取得成功,为我国图书艺术园地继续增色添彩。     

New excavations at the Barbar Temple, Bahrain

In 2004 excavations at the Barbar Temple dating to c. 2000 BC established that the function of the southeastern subterranean channel connected to the temple pool was to supply the pool with water and not to divert water away from the pool. North and west of the temple the oval terrace wall of its third phase was located. In the centre of the Northeast Temple the remains of a shaft-stairway leading down to a well-chamber was uncovered and shown to be furnished with two subterranean channels leading water into the chamber. South of the Northeast Temple a house with late pottery was excavated. Two stamp seals and two seal-impressed tokens were found.     

北宋东京汴河东水门考

本文综合研究文献记载与考古资料,认为北宋东京汴河东水门应由河道之上的水闸门、汴河南北两岸的陆行门,以及南北拐子城所组成。拐子城,系直门两重,是为了保卫上善与通津两座陆行门和汴河漕运而建,在北宋末年抗击金人的东京保卫战中,起了重要作用。张择端《清明上河图》中所绘制的那座城门,即为汴河南岸的上善门     

湖北丹江口市玉皇庙遗址调查简报

玉皇庙遗址位于湖北省丹江口市境内,现为丹江口水库中一小岛。1995年,文物工作者对南水北调工程文物调查时发现该遗址。在遗址采集新石器时代和周代遗物。新石器时代遗物与青龙泉和大寺遗址、朱家台遗址和乱石滩遗址等出土的同期遗物相近。周代遗物与官山河两岸早年发现的同期遗物相似。     

开埠初期上海租界的水环境治理

以往学界对开埠初期上海租界水环境治理,一般采取填浜筑路的视角,而本文通过对档案资料的考察发现,租界当局对租界内的河浜采取了灵活的治理办法,对于挡路和阻碍市政的死水河浜进行填埋,而对于一般的潮汐河浜和航运河浜采取了清淤、疏通的保护措施,挖掘开通了新河浜,从而使河浜水系的功能得以延续。为了排水需要,租界当局辟建了下水道系统,其治理办法却借鉴于治河方法。