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1.
Interfacial interactions, namely interfacial tension, wettability, capillarity and interfacial mass transfer are known to govern fluid distribution and behavior in porous media. Therefore the interfacial interactions between CO2, brine and oil and/or gas reservoirs have a significant influence on the effectiveness of any CO2 storage operations. However, data and knowledge of interfacial properties in storage conditions are scarce. This issue becomes particularly true in the case of deep saline aquifers where limited, economically driven, data collection and archiving are available. In this paper, we present a complete set of brine–CO2 interfacial tension data at pressure, temperature and salinity conditions, representative of a CO2 storage operation. A semi-empirical correlation is proposed to calculate the interfacial tension from the experimental data. Wettability is studied at pore scale, using glass micromodels in order to track fluids distribution as a function of the thermodynamic properties and wettability conditions for water–CO2 systems. With this approach, we show that, in strongly hydrophilic porous media, the CO2 does not wet the solid surface whereas; if the porous media has less hydrophilic properties the CO2 significantly wets the surface.  相似文献   

2.
An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO2 and brine consisting in equal molal concentrations of NaCl and CaCl2. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO2 storage in deep saline aquifers. The dependence of CO2/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO2/NaCl solution and CO2/CaCl2 solution. CO2/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO2/NaCl solution and CO2/CaCl2 solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts.  相似文献   

3.
Accurate modeling of storage of carbon dioxide (CO2) in heterogeneous aquifers requires experiments of the capillary pressure as function of temperature and pressure. We present a method with which static drainage and imbibition capillary pressures can be measured continuously as a function of saturation at various temperature (T) and pressure (P) conditions. The measurements are carried out at (TP) conditions of practical interest. Static conditions can be assumed as small injection rates are applied. The capillary pressure curves are obtained for the unconsolidated sand–distilled water–CO2 system. The experimental results show a decrease of drainage and imbibition capillary pressure for increasing CO2 pressures and pronounced dissolution rate effects for gaseous CO2. Significant capillary pressure fluctuations and negative values during imbibition are observed at near critical conditions. The measurement procedure is validated by a numerical model that simulates the experiments.  相似文献   

4.
Taking Huanglong Ravine and Kangding, Sichuan, and Xiage, Zhongdian, Yunnan, as examples, the authors summarize the hydrogeochemical and carbon stable isotopic features of the geothermal CO2-water-carbonate rock system and analyze the CO2 sources of the system. It was found that the hydrogeochemical and carbon stable isotopic features of such a system are different from those of shallow CO2-water-carbonate rock system, which is strongly influenced by biosphere. The former has higher CO2 partial pressure, and is rich in heavy carbon stable isotope. In addition, such a geothermal system is also different from that developed in igneous rock. The water in the latter system lacks Ca2+, and thus, there are few tufa deposits on ground surface, but it is rich in light carbon stable isotope. Further analysis shows that CO2 of the geothermal CO2-water-carbonate rock system is a mixture of metamorphic CO2 and magmatic CO2.  相似文献   

5.
13C and ΣCO2 data from the North and South Atlantic, the Antarctic, and the North and South Pacific are given. The δ13C of the ΣCO2 in the deep water (~3000m) decreases from 1.7‰ in the North Atlantic to ?0.10‰ in the North Pacific. This change is attributed to the addition of about 158 μmoles of CO2 per kg of seawater. The in-situ oxidation of organic matter accounts for 83% of this increase in ΣCO2, while the remainder is attributed to dissolution of calcium carbonate.The δ13C of the dissolved CO2 in mid-latitude surface water samples is controlled by a quasi-steady-state equilibrium with atmospheric CO2 at a mean temperature of 16°C. The δ13C and ΣCO2 values of Antarctic surface water samples suggest that these waters are derived from a mixture of North Atlantic deep water and equilibrated surface water.  相似文献   

6.
三峡水库澎溪河消落区土-气界面CO2和CH4通量初探   总被引:1,自引:0,他引:1  
李哲  张利萍  王琳  郭劲松  高旭  方芳  蒋滔 《湖泊科学》2013,25(5):674-680
水库近岸湿地(消落区)温室气体(CO2、CH4)产汇是水库温室气体效应问题的重要组成部分.本文以三峡水库支流澎溪河的白家溪、养鹿两处大面积消落区为研究对象,于2010年6 9月水库低水位运行期间,对近岸消落区土-气界面CO2、CH4通量进行监测.白家溪消落区土-气界面CO2通量均值为12.38±2.42 mmol/(m2·h);CH4通量均值为0.0112±0.0064 mmol/(m2·h).养鹿消落区CO2、CH4通量均值分别为10.54±5.17、0.14±0.16 mmol/(m2·h).总体上,6 9月土-气界面CO2通量呈增加趋势,而CH4通量水平呈现显著的递减趋势.消落区土地出露后植被恢复,在一定程度上促进了土壤有机质含量的增加,使得6 9月CO2释放通量的总体趋势有所增加.消落区退耕后,其甲烷氧化菌的活性得到恢复,加之在土地出露曝晒过程中土壤透气性增强,使得消落区土壤对大气中CH4吸收氧化潜势增强.尽管如此,仍需进一步的研究以明晰消落区土-气界面CO2、CH4产汇的主要影响因素.  相似文献   

7.
The selection and the subsequent design of a subsurface CO2 storage system are subject to considerable uncertainty. It is therefore important to assess the potential risks for health, safety and environment. This study contributes to the development of methods for quantitative risk assessment of CO2 leakage from subsurface reservoirs. The amounts of leaking CO2 are estimated by evaluating the extent of CO2 plumes after numerically simulating a large number of reservoir realizations with a radially symmetric, homogeneous model. To conduct the computationally very expensive simulations, the ‘CO2 Community Grid’ was used, which allows the execution of many parallel simulations simultaneously. The individual realizations are set up by randomly choosing reservoir properties from statistical distributions. The statistical characteristics of these distributions have been calculated from a large reservoir database, holding data from over 1200 reservoirs. An analytical risk equation is given, allowing the calculation of average risk due to multiple leaky wells with varying distance in the surrounding of the injection well. The reservoir parameters most affecting risk are identified. Using these results, the placement of an injection well can be optimized with respect to risk and uncertainty of leakage. The risk and uncertainty assessment can be used to determine whether a site, compared to others, should be considered for further investigations or rejected for CO2 storage.  相似文献   

8.
Expeditions during the summers of 2002 and 2003 implemented continuous monitoring of near-surface (2 m height) atmospheric CO2 and H2O concentrations at the 4500 m elevation on Muztagata. The resultant data sets reveal a slight decrease of CO2 concentrations (of about 5 μmol·mol-1) and changes in the diurnal variations from the end of June to the middle August. The daily maximum CO2 concentrations occur between 02:30-05:30 AM (local time) and the minimum levels occur between 12:00-15:30 PM. The atmospheric CO2 concentrations in the summer of 2002 were around 5 μmol·mol-1 lower than those during the same period of 2003, whereas the diurnal amplitude was higher. In contrast, we found that the daily mean atmospheric H2O content in 2003 was much lower than that in 2002 and there exists a striking negative correlation between CO2 and H2O concentrations. We therefore suggest that the near-surface atmospheric CO2 concentration is affected not only by photosynthesis and respiration, but also by the air H2O content in the glaciated region around Muztagata.  相似文献   

9.
Earth degassing specifically of carbon dioxide CO2 is of increasing interest with respect to the global carbon budget, related climate effects, earthquake and volcano eruption mechanisms, as well as plant physiological reactions in gas-rich environments. Investigations in all of these disciplines require the detection of surface CO2 degassing structures and quantification of their emissions. We introduce minimal thermal change detection based on infrared imaging as a new remote sensing tool for the detection of earth surface thermal anomalies suiting among others to discover earth degassing locations of any origin. The method allows for seamless areal search and monitoring of degassing structures in any terrain. As proof of concept infrared imaging measurements were performed at the Bossoleto vent on the eastern master fault of the Siena Graben (Tuscany, Italy). It is known for the migration of a large amount of CO2-rich gas from deep geothermal reservoirs. Field data acquired confirmed the qualification of the method. Detection of CO2 degassing locations from infrared image time series worked reliably and optimal detection conditions were identified (dry, calm, cloudless weather between dusk and dawn). A simple model of heat exchange processes involved and observed was developed. In a first attempt this model was applied to determine the gas exit temperature, the area of gas thermal reach and the gas flux from recorded image series. It is the first method that allows remote areal survey of mofette fields and the associated CO2 flux quantification sole from infrared image time series.  相似文献   

10.
湖泊、河流等内陆水体是连接陆地生态系统和海洋的“长程碳环路”的重要节点,也是温室气体二氧化碳(CO2)排放源,在调节陆地、海洋间的碳迁移转换中发挥着重要作用。相对于自然水体,城市水体因面积小、水深浅且受监测方法限制,水-气界面碳通量经常被忽略。为探讨我国亚热带城市水体温室气体排放特征,本研究以湖南省长沙市典型城市水体,包括洋湖、西湖、松雅湖、月湖4个湖泊和湘江长沙段为研究对象,分别于2022年4和10月采用光化学反馈-腔增强吸收光谱法(OF-CEAS)和扩散模型法对水-气界面CO2通量进行对比测定。结果表明,长沙城市湖泊与河流春季为CO2排放源,秋季为吸收汇,河流水-气界面CO2通量呈显著季节差异。河湖之间CO2通量在春季表现为显著差异,秋季差异不显著。CO2通量与水体溶解氧、水体总氮浓度等呈显著正相关。2种方法的CO2通量对比测定在湖泊上显著相关,但对河流而言相关性不显著。研究揭示的城市湖泊与河流CO2气体的排放特征有利于深入探究城市水体碳的迁移转化,可对全面了解全球气候变化过程和河湖湿地温室气体减排和调控提供科学支撑。  相似文献   

11.
内陆水体是大气CO2收支估算的重要组成部分。农业流域分布着大量池塘景观水体,且具备蓄洪抗旱、消纳污染、水产养殖等多种功能。但是,农业流域不同功能的小型池塘CO2排放特征尚不清楚。本研究以极具农业流域代表性的烔炀河流域为研究对象,选取流域中用于水产养殖(养殖塘)、生活污水承纳(村塘)、农业灌溉(农塘)、蓄水(水塘)的4个功能不同的景观池塘,基于为期1年的野外实地观测,以明确农业流域小型池塘CO2排放特征。结果表明,不同功能池塘水体CO2排放差异显著,受养殖活动、生活污水输入和农田灌溉等人类活动影响,养殖塘((80.37±100.39) mmol/(m2·d))、村塘((48.69±65.89) mmol/(m2·d))和农塘((13.50±15.81) mmol/(m2·d))是大气CO2的热点排放源,其CO2排放通量分别是自然蓄水塘((4.52±23.26) mmol/(m2·d))的18、11和3倍。统计分析也表明,该流域池塘CO2排放变化总体上受溶解氧、营养盐等因素驱动。4个不同景观池塘CO2排放通量全年均值为(37.31±67.47) mmol/(m2·d),是不容忽视的CO2排放源,其中养殖塘和村塘具有较高的CO2排放潜力,在未来研究中需要重点关注。  相似文献   

12.
河流作为连接陆地和海洋碳库之间的通道,是全球内陆水体碳排放最主要的载体,在全球碳循环中发挥着至关重要的作用。全球河流水-气界面二氧化碳(CO2)脱气显著的时间异质性特征研究有助于深入理解其碳循环过程与机制,也为准确评估碳通量以及完善碳循环模型提供了科学支撑。本文系统梳理了国内外的相关研究成果,总结了目前河流CO2脱气通量在昼夜、季节以及多年尺度上的动态变化及其影响因素,指出其昼夜变化与季节变化存在一定的周期性,并对不同空间尺度上CO2脱气通量的时间差异进行讨论。同时分析当前研究中的不足,认为缺乏河流二氧化碳分压(pCO2)与CO2脱气系数(k)高分辨率且长期连续的直接测量,限制了河流CO2脱气通量时间尺度变化的周期性及相互之间关系的厘定,使得气候变化与人类活动对河流CO2脱气时间动态的影响仍然难以量化与预测。最后,根据目前存在的问题,展望了未来的研究重点,为全球河流水-气界面碳循环过程与机制、模型研究提供新的思路与方向,以及可以更准确地评估和预测未来河流碳排放的变化趋势。  相似文献   

13.
A numerical simulation was conducted to predict the change of pCO2 in the ocean caused by CO2 leaked from an underground aquifer, in which CO2 is purposefully stored. The target space of the present model was the ocean above the seafloor. The behavior of CO2 bubbles, their dissolution, and the advection-diffusion of dissolved CO2 were numerically simulated. Here, two cases for the leakage rate were studied: an extreme case, 94,600 t/y, which assumed that a large fault accidentally connects the CO2 reservoir and the seafloor; and a reasonable case, 3800 t/y, based on the seepage rate of an existing EOR site. In the extreme case, the calculated increase in ΔpCO2 experienced by floating organisms was less than 300 ppm, while that for immobile organisms directly over the fault surface periodically exceeded 1000 ppm, if momentarily. In the reasonable case, the calculated ΔpCO2 and pH were within the range of natural fluctuation.  相似文献   

14.
Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO2 leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO2. In situ CO2 exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO2 in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO2 concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.  相似文献   

15.
The oxygen minimum zones (OMZs) are recognized as intense sources of N2O greenhouse gas (GHG) and could also be potential sources of CO2, the most important GHG for the present climate change. This study evaluates, for one of the most intense and shallow OMZ, the Chilean East South Pacific OMZ, the simultaneous N2O and CO2 fluxes at the air–sea interface. Four cruises (2000–2002) and 1 year of monitoring (21°–30°–36°S) off Chile allowed the determination of the CO2 and N2O concentrations at the sea surface and the analysis of fluxes variations associated with different OMZ configurations. The Chilean OMZ area can be an intense GHG oceanic local source of both N2O and CO2. The mean N2O fluxes are 5–10 times higher than the maximal previous historical source in an OMZ open area as in the Pacific and Indian Oceans. For CO2, the mean fluxes are also positive and correspond to very high oceanic sources. Even if different coupling and decoupling between N2O and CO2 are observed along the Chilean OMZ, 65% of the situations represent high CO2 and/or N2O sources. The high GHG sources are associated with coastal upwelling transport of OMZ waters rich in N2O and probably also in CO2, located at a shallow depth. The integrated OMZ role on GHG should be better considered to improve our understanding of the past and future atmospheric CO2 and N2O evolutions.  相似文献   

16.
The vertical stratification of carbon dioxide (CO2) injected into a deep layered aquifer made up of high-permeability and low-permeability layers, such as Utsira aquifer at Sleipner site in Norway, is investigated with a Buckley–Leverett equation including gravity effects. In a first step, we study both by theory and simulation the application of this equation to the vertical migration of a light phase (CO2), in a denser phase (water), in 1D vertical columns filled with different types of porous media: homogeneous, piecewise homogeneous, layered periodic and finally heterogeneous. For each case, we solve the associated Riemann problems and propose semi-analytical solutions describing the spatial and temporal evolution of the light phase saturation. These solutions agree well with simulation results. We show that the flux continuity condition at interfaces between high-permeability and low-permeability layers leads to CO2 saturation discontinuities at these interfaces and, in particular, to a saturation increase beneath low-permeability layers. In a second step, we analyze the vertical migration of a CO2 plume injected into a 2D layered aquifer. We show that the CO2 vertical stratification under each low-permeability layer is induced, as in 1D columns, by the flux continuity condition at interfaces. As the injection takes place at the bottom of the aquifer the velocity and the flux function decrease with elevation and this phenomenon is proposed to explain the stratification under each mudstone layer as observed at Sleipner site.  相似文献   

17.
通过甘东南地震危险区地震宏观异常观测实例分析,系统研究CO_2气体在地震构造活动过程中的地球化学演化过程,以及发生的一系列酸碱平衡和氧化还原化学反应。结果表明地下深部CO_2气体不仅是其他微量气体Rn等向地表方向运移的载体,而且参与酸碱平衡和氧化还原反应,是地下深部生物化学反应的重要影响条件,地震前兆及宏观异常现象的发生常伴随着CO_2的异常变化。因此CO_2气体可以作为良好的示踪气体,在地震前兆观测及重大异常落实中尤其要重视对其进行监测。  相似文献   

18.
The southern Yellow Sea (SYS), located to the north of the East China Sea (ECS), was considered part of the ECS when Tsunogai et al. (1999) proposed the “continental shelf pump” (CSP) hypothesis. However, the original CSP carbon dioxide (CO2) uptake flux (2.9 mol C m−2 yr−1) appears to have been overestimated, primarily due to the differences between the SYS and the ECS in terms of their CO2 system. In this paper, we estimated air-sea CO2 fluxes in the SYS using the surface water partial pressure of CO2 (pCO2) measured in winter, spring, and summer, as well as that estimated in fall via the relationship of pCO2 with salinity, temperature, and chlorophyll a. The results indicate that overall, the entire investigated area was a net source of atmospheric CO2 during summer, winter, and fall, whereas it was a net sink during spring. Spatially, the nearshore area was almost a permanent CO2 source, while the central SYS shifted from being a CO2 sink in spring to a source in the other seasons of the year. Overall, the SYS is a net source of atmospheric CO2 on an annual scale, releasing ∼7.38 Tg C (1 Tg=1012 g) to the atmosphere annually. Thus, the updated CO2 uptake flux in the combined SYS and ECS is reduced to ∼0.86 mol C m−2 yr−1. If this value is extrapolated globally following Tsunogai et al. (1999), the global continental shelf would be a sink of ∼0.29 Pg C yr−1, instead of 1 Pg C yr−1 (1 Pg=1015 g).The SYS as a net annual source of atmospheric CO2 is in sharp contrast to most mid- and high-latitude continental shelves, which are CO2 sinks. We argue that unlike the ECS and the North Sea where carbon on the shelf could be exported to the open ocean, the SYS lacks the physical conditions required by the CSP to transport carbon off the shelf effectively. The global validity of the CSP theory is thus questionable.  相似文献   

19.
Near-surface soil CO2 gas-phase concentration (C) and concomitant incident rainfall (Pi) and through-fall (Pt) depths were collected at different locations in a temperate pine forest every 30 min during the 2005 and 2006 growing seasons (and then averaged to the daily timescale). At the daily scale, C temporal variations were well described by a sequence of monotonically decreasing functions interrupted by large positive jumps induced by rainfall events. A stochastic model was developed to link rainfall statistics responsible for these jumps to near-surface C dynamics. The model accounted for the effect of daily rainfall variability, both in terms of timing and amount of water, and permitted an analytical derivation of the C probability density function (pdf) using the parameters of the rainfall pdf. Given the observed positive correlation between daily C and soil CO2 fluxes to the atmosphere (Fs), the effects of various rainfall regimes on the statistics of Fs can be deduced from the behavior of C under different climatic conditions. The predictions from this analytical model are consistent with flux measurements reported in manipulative experiments that varied rainfall amount and frequency.  相似文献   

20.
Partial pressure of CO2 in equilibrium with sample water (pCO2) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO2 flux calculated from the pCO2 and gas transfer coefficients ranged from −0.144 to −0.0701 g C m−2 day−1 depending on which gas transfer coefficient was used. The pCO2 before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO2 was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO2 strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO2 of 35 ppm together with the highest PPFD of 1362 μmol E m−2 s−1 were observed in the afternoon on June 28 in the presence of sea ice. The very low pCO2 observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO2 released by melting sea ice early in the season.  相似文献   

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