不同饱水条件下蚀变岩边坡稳定性分析

露天矿坑蓄水后,边坡岩体长期处于浸水状态,导致岩石抗剪强度产生弱化,对边坡的稳定性产生不利影响。为分析不同饱水条件对边坡蚀变岩抗剪强度参数的影响,对仓上金矿露天矿蚀变岩试件分别进行0、8、20、35、60、100d的饱水处理。由饱水岩样的常规三轴试验结果可得,在不同酸性环境、不同饱水时间条件下,蚀变岩的内摩擦角和粘聚力产生明显的损伤弱化,饱水时间弱化作用强于浸水溶液的酸性状态。饱水时间大于60d后,抗剪强度参数的降低幅度明显减小,饱水时间产生的弱化作用是一定的。根据不平衡推力法对划分露天边坡条块,求解边坡的安全系数,随着饱水时间的增加和浸水溶液酸性的增强,边坡的安全系数呈现显著降低趋势,边坡发生滑坡的概率逐渐增大。试验与理论研究结果可以更好的为露天矿边坡的支护设计提供重要依据。     

不同温度条件下CO2水溶液对碳酸盐岩的溶蚀作用

普遍认为酸性流体的溶蚀作用是碳酸盐岩储层形成的重要制约因素。本文以一个全新的模拟实验方式对不同类型碳酸盐岩在CO2水溶液中的相对溶蚀能力进行了研究,结果发现随温度从常温至200℃,碳酸盐岩的溶蚀能力由弱变强再变弱,在60～90℃区间内溶蚀能力最强。白云岩不管在低温还在高温环境下,总比灰岩更难溶蚀,过渡类型的岩类介于二者之间,当温度大于150℃后,CO2对碳酸盐岩的溶蚀能力变得越来越弱。灰岩与白云岩的溶蚀差异也变得越来越小。这暗示碳酸盐岩在早成岩晚期—中成岩早期,CO2水溶液对灰岩的溶蚀作用有重要影响,而对白云岩的溶蚀作用影响较小,白云岩优质储层的形成可能与碳酸盐岩中钙质的流失或白云岩化作用有关。     

Reactivity of micas and cap-rock in wet supercritical CO2 with SO2 and O2 at CO2 storage conditions

Seal or cap-rock integrity is a safety issue during geological carbon dioxide capture and storage (CCS). Industrial impurities such as SO₂, O₂, and NOx, may be present in CO₂ streams from coal combustion sources. SO₂ and O₂ have been shown recently to influence rock reactivity when dissolved in formation water. Buoyant water-saturated supercritical CO₂ fluid may also come into contact with the base of cap-rock after CO₂ injection. Supercritical fluid-rock reactions have the potential to result in corrosion of reactive minerals in rock, with impurity gases additionally present there is the potential for enhanced reactivity but also favourable mineral precipitation.The first observation of mineral dissolution and precipitation on phyllosilicates and CO₂ storage cap-rock (siliciclastic reservoir) core during water-saturated supercritical CO₂ reactions with industrial impurities SO₂ and O₂ at simulated reservoir conditions is presented. Phyllosilicates (biotite, phlogopite and muscovite) were reacted in contact with a water-saturated supercritical CO₂ containing SO₂, or SO₂ and O₂, and were also immersed in the gas-saturated bulk water. Secondary precipitated sulfate minerals were formed on mineral surfaces concentrated at sheet edges. SO₂ dissolution and oxidation resulted in solution pH decreasing to 0.74 through sulfuric acid formation. Phyllosilicate dissolution released elements to solution with ∼50% Fe mobilized. Geochemical modelling was in good agreement with experimental water chemistry. New minerals nontronite (smectite), hematite, jarosite and goethite were saturated in models. A cap-rock core siltstone sample from the Surat Basin, Australia, was also reacted in water-saturated supercritical CO₂ containing SO₂ or in pure supercritical CO₂. In the presence of SO₂, siderite and ankerite were corroded, and Fe-chlorite altered by the leaching of mainly Fe and Al. Corrosion of micas in the cap-rock was however not observed as the pH was buffered by carbonate dissolution. Ca-sulfate, and Fe-bearing precipitates were observed post SO₂-CO₂ reaction, mainly centered on surface cracks and an illite rich illite-smectite precipitate quantified. Water saturated impure supercritical CO₂ was observed to have reactivity to rock-forming biotite, muscovite and phlogopite mineral separates. In the cap-rock core however carbonates and chlorite were the main reacting minerals showing the importance of assessing actual whole core.     

热液条件下CO2和H2反应合成丁烷和戊烷

热液条件下CO2和H2通过费托合成反应产生烷烃从热力学上来说是可行的,但是,前人的实验研究表明,如果没有合适的催化剂,该反应难以进行,并且烷烃产物的种类依赖于催化剂的种类和性质.在镍铁矿的催化作用下,热液中的CO2和H2能够反应形成CH4,在铬铁矿催化作用下反应能够产生CH4、C2H6和C3Ha.热液条件下,CO2和H2能否反应形成碳数大于3的烷烃,还需要进一步的催化实验加以查证.本研究在300℃、30 MPa条件下进行实验,以Fe、CoCl2和13C标识的NaH13CO3在NaCl溶液中反应.13C同位素示踪结果表明,实验反应过程中CO2和H2反应形成了丁烷和戊烷.     

CO2矿化封存条件下玄武岩溶解反应速率模型

实施CO2补集与地质封存是目前降低大气中CO2含量、减轻温室效应的有效途径。在所能利用的封存方式中,CO2矿化封存最为安全、稳定。在能实施矿化封存的岩石介质中,玄武岩封存潜力巨大,且岩石溶解反应过程是矿化沉淀过程的基础;因此,研究玄武岩溶解反应速率十分必要。在构成玄武岩的单一矿物与缓冲溶剂的反应速率模型的基础上,提出不同温度下玄武岩样品在超临界CO2水溶液中的溶解速率模型,并通过室内实验,利用采自山东省临朐县的玄武岩岩心样品,在45~100 ℃、10 MPa条件下,与超临界CO2－纯水反应,并运用最小二乘法确定模型中相关参数。同时利用57 ℃、72 ℃、92 ℃ 3个温度下的模型计算值与实验值对模型进行验证,结果证明了模型的准确性和可靠性,研究结果可直接应用于CO2地质封存条件下玄武岩溶解速率的计算。     

Dissolution of Columbia River Basalt under mildly acidic conditions as a function of temperature: Experimental results relevant to the geological sequestration of carbon dioxide

Increasing attention is being focused on the rapid rise of CO₂ levels in the atmosphere, which many believe to be the major contributing factor to global climate change. Sequestering CO₂ in deep geological formations has been proposed as a long-term solution to help stabilize CO₂ levels. However, before such technology can be developed and implemented, a basic understanding of H₂O–CO₂ systems and the chemical interactions of these fluids with the host formation must be obtained. Important issues concerning mineral stability, reaction rates, and carbonate formation are all controlled or at least significantly impacted by the kinetics of rock–water reactions in mildly acidic, CO₂-saturated solutions. Basalt has recently been identified as a potentially important host formation for geological sequestration. Dissolution kinetics of the Columbia River Basalt (CRB) were measured for a range of temperatures (25–90 °C) under mildly acidic to neutral pH conditions using the single-pass flow-through test method. Under anaerobic conditions, the normalized dissolution rates for CRB decrease with increasing pH (3 ? pH ? 7) with a slope, η, of −0.15 ± 0.01. Activation energy, E_a, has been estimated at 32.0 ± 2.4 kJ mol⁻¹. Dissolution kinetics measurements like these are essential for modeling the rate at which CO₂-saturated fluids react with basalt and ultimately drive conversion rates to carbonate minerals in situ.     

Feasibility study of CO2 geological storage in China

It has been proved to be one effective means to reduce emissions of CO2 to mitigate the worsening global climate change through lots of projects and tests about CO2 geological storage. The sites that are suitable for CO2 geological storage include coal seams that can not be mined, deep saline aquifers, oil fields, and depleted gas fields. The emission of CO2 from fuel combustion is about 3.54 Gt in China in 2003, which is the second biggest in the world. Because the energy consumption in China mainly depends on fossil fuels for a long time in the future, China will become a country with the biggest emission of CO2 in the world, which will make China have to reduce the emissions of CO2 by some methods including geological storage. Based on lots of information about the reserves of coal seam methane and the rank of coal in the 68 coal basins in China, the total CO2 storage capacity in these coal basins was estimated according to the recovery coefficient and exchange ratio of CO2 to CHa.The total storage capacity in deep saline aquifers can be regarded as the total quantity of CO2 that can be dissolved in the saline aquifers at the depth from 1000m to 3000m under ground. The quantity can be estimated by multiplying the solubility of CO2 in the saline water and the volume of the appropriate aquifers. According to the reserve and quality of crude oil in 46 main oil basins in China, the CO2 storage capacity and the quantity of enhanced oil were calculated. The storage capacity of depleted gas fields can be derived from the reserve and depth of the gas fields. The total CO2 geological storage capacity is about 196.2 Gt CO2 that is as against 55.4 times the CO2 emission from fuel combustion in China in 2003. According to the results of the finished projects and tests about CO2-EOR and CO2-ECBM, the CO2 geological storage capacities in coal seams, deep saline aquifers, oil fields and depleted gas fields will be estimated.     

我国沉积盆地CO2地质储存的地热条件适宜性评价

CO2地质储存是减少人类活动产生的CO2向大气排放的有效措施之一。目前CO2地质储存适宜性评价中仅把地热条件作为单一因子进行考虑,难以准确评价地热条件对CO2地质储存的影响,评价精度较差。为此本文采用加权法将地热条件三因素(大地热流、地温梯度与地表年均气温)进行CO2地质储存适宜性评价,提高了精度。表明:我国总体上较适宜CO2地质储存,储存空间大。2.1%(8.5×104km2)沉积盆地适宜CO2地质储存,68.6%(274.0×104km2)较适宜,24.6%(98.4×104km2)一般适宜,4.7%较不适宜(18.7×104km2),无不适宜区。     

Establishment of an assessment method for site-scale suitability of CO2 geological storage

Geological storage of CO2 (known as geological sequestration) is increasingly seen as a viable strategy to reduce the release of greenhouse gases into the atmosphere. China has become one of the largest emitters of CO2 in the world. Therefore, alongside other emissions reductions measures, the deployment of geological storage projects to capture CO2 in China is essential. This paper focuses on the establishment of qualitative and quantitative assessment methods for site-scale suitability of CO2 geological storage in deep saline formation systems. This is based on numerical modelling prior to the development a specific geological storage project, providing a more accurate selection of preferential sites from a list of potential storage locations. However, the detailed design of specific geological storage projects was not con?sidered.     

Numerical computations of rock dissolution and geomechanical effects for CO2 geological storage

The paper is motivated by the long‐term safety analysis of the CO₂ geological storage. We present a methodology for the assessment of the geomechanical impact of progressive rock dissolution. The method is based on the use of X‐ray tomography and the numerical dissolution technique. The influence of evolution of the microstructure on the macroscopic properties of the rock is analysed by using periodic homogenization method. The numerical computations show progressive degradation of all components of the stiffness (orthotropic) tensor. Moreover, the evolution of associated mass transfer properties (as tortuosity and conductivity tensors), by using the periodic homogenization method, is also calculated. The correlation between the mechanical parameters and the transfer properties during the dissolution process is presented. The results show that the highest increase of the hydraulic conductivity (in direction Y) is not associated with the highest decrease of Young modulus in this direction. Moreover, the highest decrease of Young modulus (in the direction X) is not associated with percolation in this direction. Finally, an incremental law to calculate settlement, in case of a rock with evolving microstructure, is proposed. The solution of the macroscopic settlement problem under constant stress and drained conditions showed that the geomechanical effects of the rock dissolution are rather limited. Copyright © 2014 John Wiley & Sons, Ltd.     

渗透率的非均质性对CO_2地质封存的影响

CO2地质封存可以减少化石燃料燃烧排放的CO2量,有效减缓温室效应。储层渗透率可以决定CO2通道的形成,进而改变其在储层中的运移规律,因而是影响CO2地质封存的重要因素。根据研究区基本地质数据、三维地震勘探结果和统计规律确定了渗透率的分布情况,运用储层多相流模拟软件TOUGH2-MP分析了渗透率的非均质性对CO2地质封存的影响。结果表明:(1)渗透率的分布情况对CO2储存量和注入压力的影响很大,相比于均值模型,CO2的注入总量明显减少,到达最大允许压力积聚所需的时间要比均质模型短;(2)在保证注入速率和压力积聚不超过允许最大值的双重要求下,定压和定量两种注入方案都有待改进,建议考虑如人工压裂等工程措施;(3)渗透率的非均质性使得CO2晕呈现出不规则扩散,经过20年的注入,其最大扩散距离约800m,比均质情况下小150m,须做好相应的监测工作。     

Development of detection and monitoring techniques of CO2 leakage from seafloor in sub-seabed CO2 storage

Carbon dioxide capture and storage (CCS) in sub-seabed geological formations is currently being studied as a potential option to mitigate the accumulation of anthropogenic CO₂ in the atmosphere. To investigate the validity of CO₂ storage in the sub-seafloor, development of techniques to detect and monitor CO₂ leaked from the seafloor is vital. Seafloor-based acoustic tomography is a technique that can be used to observe emissions of liquid CO₂ or CO₂ gas bubbles from the seafloor. By deploying a number of acoustic tomography units in a seabed area used for CCS, CO₂ leakage from the seafloor can be monitored. In addition, an in situ pH/pCO₂ sensor can take rapid and high-precision measurements in seawater, and is, therefore, able to detect pH and pCO₂ changes due to the leaked CO₂. The pH sensor uses a solid-state pH electrode and reference electrode instead of a glass electrode, and is sealed within a gas permeable membrane filled with an inner solution. Thus, by installing a pH/pCO₂ sensor onto an autonomous underwater vehicle (AUV), an automated observation technology is realized that can detect and monitor CO₂ leakage from the seafloor. Furthermore, by towing a multi-layer monitoring system (a number of pH/pCO₂ sensors and transponders) behind the AUV, the dispersion of leaked CO₂ in a CCS area can also be observed. Finally, an automatic elevator can observe the time-series dispersion of leaked CO₂. The seafloor-mounted automatic elevator consists of a buoy equipped with pH/pCO₂ and depth sensors, and uses an Eulerian method to collect spatially continuous data as it ascends and descends.Hence, CO₂ leakage from the seafloor is detected and monitored as follows. Step 1: monitor CO₂ leakage by seafloor-based acoustic tomography. Step 2: conduct mapping survey of the leakage point by using the pH/pCO₂ sensor installed in the AUV. Step 3: observe the impacted area by using a remotely operated underwater vehicle or the automatic elevator, or by towing the multi-layer monitoring system.     

CO2 geological storage: The environmental mineralogy perspective

Geological storage of carbon dioxide (CO₂) is one of the options envisaged for mitigating the environmental consequences of anthropogenic CO₂ increases in the atmosphere. The general principle is to capture carbon dioxide at the exhaust of power plants and then to inject the compressed fluid into deep geological formations. Before implementation over large scales, it is necessary to assess the efficiency of the process and its environmental consequences. The goal of this paper is to discuss some environmental mineralogy research perspectives raised by CO₂ geological storage.     

The recognition of hydrothermal processes in the trace element geochemistry of uranium- and thorium-enriched tuffaceous rocks, Northwest Iran

Radiometrically anomalous tuffaceous rocks occur as conformable lenses in a volcano-sedimentary sequence of Neogene age near the village of Sarkhanlu, northwest Iran. The anomalous rocks have been extensively altered by hydrothermal fluids, and kaolinization and silicification are widespread. 250 samples of the anomalous and background tuffs and other sediments have been analyzed for Fe, Mn and 18 trace elements. Enhanced levels of Ag, As, Mo, Pb, Sn, Sr, Th, U, W and Zr indicate an alkaline volcanic origin of the tuffaceous material, and the elements of this association dominate the statistical analysis of the geochemical data. Maximum U and Th values are among the highest ever recorded in extrusive volcanic rocks. A zone of kaolinization contains increased levels of U, Th, Pb and Sr relative to the unaltered country rock, although nine other elements are depleted in the zone. This association of elements is recognized in the radiometrically anomalous lithologies, particularly in the kaolinized tuffs, and indicates the availability of U in the hydrothermal fluids causing the alteration. Although U mineralization has not yet been found at Sarkhanlu, comparisons with the similar geological environment in central Italy and elsewhere suggest possible exploration criteria for the future. Distinct sedimentary U associations have been defined in tuffs with only background radioactivity and in dark, calcareous shales.     

盐岩CO2处置相关研究进展

现代工业生产排放了大量的CO2,为了缓解CO2造成的温室效应,对CO2进行捕获并进行地下处置是减少CO2排放量的一个有效可行的措施。在各种地下处置方法和介质中,利用盐岩溶腔进行CO2地下处置具有单个溶腔处置量大、注入速度快等优点。简要介绍了盐岩CO2地下处置存在的主要岩石力学问题,即溶腔内存在长期增压的过程。综述了影响溶腔内压的主要因素及其相互耦合作用的研究进展。这些因素包括：盐岩的蠕变性、CO2的高压缩性、盐岩在高应力下的渗透性、CO2沿管鞋的渗漏等。由于我国CO2排放的持续增加,结合我国层状盐岩的地质条件和力学特性,对各种因素的耦合作用的理论研究是今后的一个重要研究方向。     

深部咸水层二氧化碳封存的干化效应及选址启示

将二氧化碳注入到深部咸水层中,形成复杂的多组分、多相流系统。二氧化碳在压力梯度、浓度差作用下不断扩散,逐步带走盐溶液中的水分,导致各组分的相态变化,盐结晶析出,阻塞了咸水层孔隙通道,从而降低了二氧化碳的注入效率,研究该干化效应的影响因素并为工程选址提供依据具有重要意义。采用二维径向模型建立多相流体的流动方程,并结合相对渗透率和毛细压力方程探讨二氧化碳注入速率、咸水层含盐量、毛细压力的特征参数对干化效应的影响,干化效应可用固体饱和度值进行定量描述。结果表明：二氧化碳运移分3个区域：干涸区、气液相混合区及液相咸水区,干化效应主要发生在井周的干涸区。在毛细作用下固体饱和度随注入速率的减小而增大,随咸水层含盐量增大而增大,随毛细作用增大而增大。因此,提高二氧化碳的注入速率,向咸水层中注水稀释含盐量或选择粒径较大的均质咸水层减小毛细作用,均可降低盐结晶对孔隙通道的阻塞,提高注入效率。     

深部咸水层CO2地质储存地质安全性评价方法研究

CO2地质储存工程属于环保型工程项目,地质安全性是影响CO2长期封存的首要因素。深部咸水层CO2地质储存地质安全性影响因素主要包括盖层适宜性、场地地震安全性、水文地质条件、地面场地地质条件四个方面,其中盖层适宜性是CO2安全储存的最关键因素,场地地震安全性和水文地质条件次之,而地面场地地质条件也是影响工程施工的重要因素。本文基于CO2地质储存的地质安全性影响因素分析,建立了层次分析结构的地质安全性评价指标体系,并初步计算了评价指标的权重;提出可以利用模糊综合评价方法进行深部咸水层CO2地质储存地质安全性综合评价,为中国深部咸水层CO2地质储存的地质安全性评价方法和安全选址指明了方向。     

Modeling, parameterization and evaluation of monitoring methods for CO2 storage in deep saline formations: the CO2-MoPa project

Capture and geological sequestration of CO₂ from large industrial sources is considered a measure for reducing anthropogenic emissions of CO₂ and thus mitigating climate change. One of the main storage options proposed are deep saline formations, as they provide the largest potential storage capacities among the geologic options. A thorough assessment of this type of storage site therefore is required. The CO₂-MoPa project aims at contributing to the dimensioning of CO₂ storage projects and to evaluating monitoring methods for CO₂ injection by an integrated approach. For this, virtual, but realistic test sites are designed geometrically and fully parameterized. Numerical process models are developed and then used to simulate the effects of a CO₂ injection into the virtual test sites. Because the parameterization of the virtual sites is known completely, investigation as well as monitoring methods can be closely examined and evaluated by comparing the virtual monitoring result with the simulation. To this end, the monitoring or investigation method is also simulated, and the (virtual) measurements are recorded and evaluated like real data. Application to a synthetic site typical for the north German basin showed that pressure response has to be evaluated taking into account the layered structure of the storage system. Microgravimetric measurements are found to be promising for detecting the CO₂ phase distribution. A combination of seismic and geoelectric measurements can be used to constrain the CO₂ phase distribution for the anticline system used in the synthetic site.