黏土矿物组构对水化作用影响评价

泥页岩水化过程中黏土矿物起着主要的作用,但目前还缺少相关的定量描述研究。为此,利用SEM、X-粉晶衍射技术,对采自不同地区的泥岩和板岩在干燥状态、不同浸泡时间后的微观结构和含量进行分析及研究,分析黏土矿物的组构随浸泡时间的变化过程,并定量地分析其对水化过程的影响规律,研究泥页岩的软化过程。研究认为,（1）泥页岩、板岩中影响水化过程的内在因素是蒙脱石、高岭石、绿泥石和伊利石等黏土矿物的含量;（2）黏土矿物定向排列时水化作用效果较无序排列时的明显;（3）泥页岩的水化作用是一个渐进的过程,即在水化过程中流体介质首先使表面的黏土矿物软化,产生掉块;随着时间延长,流体沿裂缝、层理面向岩石内部渗透,黏土土矿物发生膨胀;无围岩限制作用时坍塌掉块持续发生;（4）泥浆中加入一定的无机盐有助于抑制水化过程的发生;压力增加将抑制水化过程的产生;温度升高则能促进泥页岩的水化过程。     

Thermomechanical model of hydration swelling in smectitic clays: I two-scale mixture-theory approach

A thermomechanical theory of hydration swelling in smectitic clays is proposed. The clay is treated as a three-scale swelling system wherein macroscopic governing equations are derived by upscaling the microstructure. At the microscale the model has two phases, the disjoint clay platelets and adsorbed water (water between the platelets). At the intermediate (meso) scale (the homogenized microscale) the model consists of clay particles (adsorbed water plus clay platelets) and bulk water. At the macroscale the medium is treated as an homogenized swelling mixture of clay particles and bulk-phase water with thermodynamic properties defined everywhere within the macroscopic body. In Part I, the mesoscopic model governing the swelling of the clay particles is derived using a mixture-theoretic approach and the Coleman and Noll method of exploitation of the entropy inequality. Application of this procedure leads to two-scale governing equations which generalize the classical thermoelastic consolidation model of non-swelling media, as they exhibit additional physico-chemical and viscous-type terms accounting for hydration stresses between the adsorbed fluid and the clay minerals. In Part II the two-scale model is applied to a bentonitic clay used for engineered barrier of nuclear waste repository. The clay buffer is assumed to have monomodal character with most of the water essentially adsorbed. Further, partial results toward a three-scale thermomechanical macroscopic model including the bulk phase next to the swelling particles are derived by homogenizing the two-scale model with the bulk water. A notable consequence of this three-scale approach is that it provides a rational basis for the appearance of a generalized inter-phase mass transfer between adsorbed and bulk water. Copyright © 1999 John Wiley & Sons, Ltd.     

Influence of Hematite Coating on the Activation of the Swelling Potential of Smectite-Bearing Rocks

The fraction of swelling-type clay minerals (smectites) is a first measure to estimate the swelling potential of natural rocks. This swelling potential is only activated if water can be incorporated in the sheet silicates. The samples studied in this work are volcanic rocks from the Southern Andes. According to the petrographic and mineralogical studies, the rocks are characterized as vulcanite with high content of smectite. Undisturbed samples showed minor swelling behaviour in conventional swelling tests, although X-ray diffraction and differential thermal analysis revealed swelling clay contents of more than 70 % in some samples. Powder swelling tests were performed on ground and recompacted rock samples. The results of these tests show a better agreement with those expected according to the mineralogical composition of the samples. The reason for the non-activation of the swelling potential in undisturbed samples was suspected to be the influence of the iron-oxide/hydroxide content, which was on average around 11 %. Scanning electron microscope images showed that the edge terminations of the clay particles are coated with hematite. The hydrophobic properties of hematite impede the access of water between the interlayers of the clay minerals and, in addition, hematite cementation prevents the expansion. In a further series of swelling tests water was replaced by a reducing solution (0.1 molar hydroxylammonium chloride) which removes the Fe-oxide coating. It can be shown that thus the swelling potential of the clay minerals in such undisturbed rocks can be activated.     

A Non-Isothermal Constitutive Model for Chemically Active Elastoplastic Rocks

Hydration/dehydration of water-active rocks under non-isothermal conditions is encountered in many industries, in particular the drilling industry. Water-active rocks can adsorb water on their basal crystal surfaces on both the external, and, in the case of expanding lattice clays, the inter-layer surfaces. There are two main mechanisms in which the instability may occur for a structure built in water-active rocks. First mechanism is the change in stresses resulted from mechanical, hydraulic, chemical and thermal interaction, which we formulate based on the concept of non-equilibrium thermodynamics. Second mechanism illustrates the change in mechanical properties of the rock due to physic-chemical interaction between the rock and exposed fluid. We postulate the later mechanism in terms of chemically active plastic deformation by using the modified Cam Clay model. The complete governing equations for non-isothermal chemo-poro-elastoplastic rock are therefore presented. A three-dimensional finite element model is then developed to solve the obtained governing equations. From the numerical results, it was found that the effect of temperature coupling term on stress cannot be ignored when non-isothermal conditions are encountered. However, this effect is almost trivial on pore pressure. It was also revealed that the effect of change in the shale’s mechanical properties on stability due to physic-chemical interaction is as important as change in stresses due to mechanical, hydraulic, chemical and thermal interactions.     

Clay swelling — A challenge in the oilfield

Water-based drilling fluids are increasingly being used for oil and gas exploration, and are generally considered to be more environmentally acceptable than oil-based or synthetic-based fluids. Unfortunately, their use facilitates clay hydration and swelling. Clay swelling, which occurs in exposed sedimentary rock formations, can have an adverse impact on drilling operations and may lead to significantly increased oil well construction costs. Minimizing clay swelling is therefore an important area attracting a large amount of interest from both academia and industry. To effectively reduce the extent of clay swelling the mechanism by which clay minerals swell needs to be understood so that efficient swelling inhibitors may be developed. Acceptable clay swelling inhibitors must not only significantly reduce clay hydration, but must also meet increasingly stringent environmental guidelines while remaining cost effective. The development of these inhibitors, which are generally based upon water soluble polymers, therefore represents a challenge to oilfield geochemistry. This review aims to provide a comprehensive understanding of the mechanism by which clay minerals swell and what steps have been taken in the development of effective and environmentally friendly clay swelling inhibitors.     

岩石变形对粘土矿物结晶生长影响的初步研究——以江西金山金矿为例

作为流体作用过程中水—岩反应的产物，粘土矿物可以帮助人们认识水—岩反应的机制和流体活动的特征。本文以江西金山金矿为例，通过对热液蚀变粘土矿物伊利石和绿泥石结晶度、平均结晶大小和晶格应变的测定，讨论了岩石变形对伊利石和绿泥石结晶生长差异的影响。在岩石应变较弱、水／岩比较小的糜棱岩带，伊利石的平均结晶大小与结晶度成负相关，而在岩石应变较强、水／岩比较大的超糜棱岩带，绿泥石的平均结晶大小与结晶度成正相关。由应变较弱的蚀变糜棱岩带到应变较强的蚀变超糜棱岩带，伊利石的结晶度有变小的趋势，而绿泥石的结晶度则基本保持不变。认为在成矿流体作用过程中，粘土矿物的形成和特点不仅受水／岩比的影响，而且在岩石变形过程中，岩石的应变和恢复速率也影响粘土矿物的结晶大小；伊利石和绿泥石平均结晶大小与其结晶度之间的关系可以反映岩石变形的机制和行为。     

Stability problems in water tunnels caused by expandable minerals. Swelling pressure measurements and mineralogical analysis

To improve the water supply in Bogota, Colombia, 38 km of tunnels were excavated through the Cretaceous and Tertiary sedimentary rocks. After four months in operation, a number of fall-outs and slides in the shotcrete-lined parts of the longest tunnel stopped the water flow completely. The majority of the fall-outs occurred in the Fomeque formation, which is dominated by black shales with interbedded layers of siltstone and some limestones.

Several rock samples from the Fomeque formation have been analyzed with respect to swellability and petrography/mineralogy. Swelling pressures varying from 014 MPa (siltstone) to 45 MPa (shale) have been measured on intact rock specimens. The siltstone does not show cracking or slaking after storage in water for several weeks. The shale disintegrates almost immediately when submerged. Representative samples of the two rock types were chosen for comprehensive mineralogical and textural analyses. The rocks show a marked difference in textures. The siltstone is homogeneous, massive and cryptocrystalline to fine grained, while the shale is microcrystalline to cryptocrystalline with a penetrative slaty cleavage.

Before the tunnel was filled with water, extensive draining and drying-out of the rock masses along the tunnel periphery took place. This resulted in heavy cracking and fissuring, especially along the cleavage planes of the shales. The cracking reduced the general strength of the rocks, but, more importantly, caused a dramatic increase in the permeability and in the exposed rock surface area. When the tunnel was filled, water entered all new fissures in the shales and the exposed and partly dehydrated illite/smectite started to swell. The swelling of the mixed layered silicates is believed to be the initiating factor causing most of the fall-outs and slides in the Chingaza tunnel.     

On the Time-Development of Sulphate Hydration in Anhydritic Swelling Rocks

Anhydritic claystones are among the most problematic rocks in tunnelling. Their swelling has caused serious damage and high repair costs in a number of tunnels, especially in Switzerland and southwest Germany. The swelling is usually attributed to the transformation of anhydrite into gypsum. It is a markedly time-dependent process which might take several decades to complete in nature. The present paper focusses on simultaneous anhydrite dissolution and gypsum precipitation in a closed system, i.e. disregarding the transport processes that may also be important for the evolution of the swelling process. The paper begins with a presentation of the governing equations and continues with parametric studies in order to investigate the role of the initial volumetric fractions of the constituents and the specific surface areas of the minerals involved. A simplified model for the hydration of anhydrite is also proposed, which identifies the governing process and the duration of the swelling process. Finally, parametric studies are performed in order to investigate the effect of the anhydrite surface being sealed by the formation of gypsum. The latter slows down the swelling process considerably.     

基于扫描电镜和CT成像技术的碳酸盐岩溶蚀作用微观结构和变化规律研究

为研究溶蚀作用下碳酸盐岩孔隙的演变规律及控制作用,文章选取三峡地区4种类型碳酸盐岩开展溶蚀实验。同时结合扫描电镜、CT成像对实验前后岩石的溶蚀特征及孔隙结构进行测试。结果表明:溶蚀总发生在低晶格能的矿物处且沿矿物晶体的菱形解理面以及薄弱部位发育,表现为对矿物和孔隙等结构的选择性溶解;碳酸盐岩的孔隙度对溶蚀过程影响较小,岩石的孔径大小是影响碳酸盐岩溶蚀速率的重要因素;小孔径岩石的溶蚀多在样品表面发育小型溶孔,大孔径岩石的溶蚀主要发生在孔隙隙壁且有向岩石内部溶蚀的痕迹;经溶蚀改造,孔喉半径和连通性均呈现出增长趋势。本研究对碳酸盐岩差异性岩溶作用机理及岩溶发育规律的认识有一定指导意义。      

Intergranular coesite and coesite inclusions in dolomite from the Dabie Shan: Constraints on the preservation of coesite in UHP rocks

Intergranular coesite is extremely rare in, and bears crucial information on the formation and preservation of, ultrahigh‐pressure (UHP) rocks. Here, we report the first occurrence of intergranular coesite in a metasedimentary rock, which occurs in the Ganjialing area in the Dabie Shan, east‐central China, and contains abundant coesite inclusions in both garnet and dolomite. We investigated the content of structural water in these minerals with Fourier transform infrared spectroscopy. Our new results undermine the ubiquity of the “pressure‐vessel” model and highlight the role of reaction kinetics in preserving coesite due to the availability of water in UHP rocks.     

A strontium isotopic study of formation waters from the Illinois basin, U.S.A.

The isotopic composition of Sr has been measured in 73 formation-water samples from Paleozoic strata in the Illinois basin; ⁸⁷Sr/⁸⁶Sr ratios range from 0.7079 to 0.7108. With the exception of four samples, the waters are more radiogenic than corresponding Paleozoic sea-water values. The relatively narrow range of slightly elevated ⁸⁷Sr/⁸⁶Sr rations is uniformly distributed in waters throughout the stratigraphic column and in Silurian waters across the basin. Isotopic analyses of core samples from reservoir rocks show an absence of water-rock Sr isotopic equilibration. Basin lithology and analyses of detrital rock units indicate that clay minerals in shales and in quartz sandstone matrices represent the only significant source of radiogenic Sr for the waters. Silurian and Devonian water show a two-component mixing relation which suggests that they comprise a single hydrogeological system that evolved when radiogenic water from New Albany shales entered Silurian-Devonian carbonate rocks and mixed with marine interstitial water. Regional migration of the waters and associated petroleum within the Silurian-Devonian strata, proposed in other studies, is consistent with the Sr isotopic data. Under favorable circumstances subsurface waters are capable of retaining a Sr isotopic recor of their evolution.     

西秦岭地区钙碱质火山岩中石榴石的发现及其地质意义

在西秦岭钙碱质火山岩中首次发现富铁铝成分的石榴石，成分与国外已有资料相比明显地富Ca。在证据表明，区内火山岩中石榴石不是外来捕获晶或残留相，而是偏“干”的岩浆处于早期高压环境下的结晶相。石榴石晶体周边生长的斜长石晶环并不是岩浆反应产物，而是岩浆在温压突变条件下以被消融残留的石榴石为中心从岩浆中直接晶出的。依据地质和实验岩石学资料推断，西秦岭中生代含石榴石钙碱质火山岩浆可能起源于50km以下的地壳基底。     

渝东北地区龙马溪组页岩吸水特性及对其力学性质的影响

页岩中含有一定量的黏土矿物，在与水基压裂液接触后会表现出与泥岩相同的膨胀特性和强度弱化效应，进而引起套管外载增加，在页岩储层压裂过程中套管出现不同程度的变形问题。以渝东北地区龙马溪组页岩为研究对象，开展不同溶液体系下页岩的自吸、膨胀特性物理实验，分析页岩水化对其岩石力学特性的影响。结果表明:页岩吸水量与时间呈对数递增关系，在不同溶液体系中，吸水量大小表现为蒸馏水 > 地层水 > 滑溜水，含有减阻剂浓度小的滑溜水体系更利于减弱页岩的吸水能力；页岩膨胀率与时间呈逐渐增长趋势，黏土矿物含量、围压和溶液体系对页岩膨胀率影响明显，相对于黏土含量，围压对膨胀率影响更加明显，页岩在溶液体系中的膨胀性能表现为蒸馏水 > 地层水 > 滑溜水；页岩的抗压强度和弹性模量都随着水化时间的增加整体呈线性递减规律。研究结果对完井过程套管强度设计具有一定的指导意义。      

烃源岩催化酯生烃动力学研究——以东营凹陷沙河街组三、四段烃源岩为例

烃源岩生烃动力学广泛应用于含油气盆地烃源岩评价与勘探中。为模拟低成熟烃源岩的实际沉积环境,实验选取了抽提有机质后的东营凹陷下第三系沙河街组三、四段烃源岩为矿物催化剂,以十八烷酸甲酯为模型化合物,在高压下做矿物低温催化脂肪酸酯脱羧生烃动力学实验。求取了化学反应的动力学参数,并分析了烃源岩层段的pH值与Eh值。结果表明,矿物对脂肪酸酯的脱羧生烃具有明显的催化作用,用连串反应模型处理脂肪酸酯的水解反应基本上为一级反应,而生烃反应则基本上为零级反应。认为对于同一类型的烃源岩,其所处的氧化还原环境对有机质的生烃有较大的影响;而对于不同的烃源岩,矿物的组成则起着非常重要的作用。     

裂谷盆地的火山热液活动和油气生成

我国东部裂谷盆地主力烃源岩中均不同程度地发育有玄武岩和辉长岩等基性火成岩,并且伴有规模不等的热液活动。火山热液活动会给烃源岩带来热量,促使有机质快速生烃和异常成熟。玄武岩活动期间的热液作用为烃源岩提供了大量矿物质和养料,使周围泥质岩富含碳酸盐和有机质,可以形成优质烃源岩;热液活动向烃源岩提供了大量过渡金属元素,作者的实验证明了过渡金属对有机质生烃具有强烈的催化作用,使烃源岩在较低温度下生成较多数量的油气;火成岩周围的烃源岩可以提前进入生烃门限。     

柴达木盆地西部第三系盐湖相有效生油岩的识别

柴达木盆地西部第三系发现了储量可观的油气资源,但是总体上讲这里的生油层钙质含量高、有机质丰度低;如何识别有效生油岩,正确评价油气资源潜量,成为这里油气勘探和地球化学的首要问题。通过上、下干柴沟组生油岩的沉积特征和地球化学分析,可发现盐湖相存在许多有机质丰度较高的生油岩;利用热解和模拟实验等方法确定出有效生油岩的有机碳含量下限为 0.4%。这样既为该区生油岩提供了评价标准,又找到大量有效生油岩,解决了研究区油气资源预测的基本问题.     

Major and trace element compositions (including REE) of mineral,thermal, mine and surface waters in SW Germany and implications for water–rock interaction

The near-surface water cycle in a geologically complex area comprises very different sources including meteoric, metamorphic and magmatic ones. Fluids from these sources can react with sedimentary, magmatic and/or metamorphic rocks at various depths. The current study reports a large number of major, minor and trace element analyses of meteoric, mineral, thermal and mine waters from a geologically well-known and variable area of about 200 × 150 km in SW Germany. The geology of this area comprises a Variscan granitic and gneissic basement overlain in parts by Triassic and Jurassic shales, sandstones and limestones. In both the basement and the sedimentary rocks, hydrothermal mineralization occurs (including Pb, Cu, As, Zn, U, Co and many others) which were mined in former times. Mineral waters, thermal waters and meteoric waters flowing through abandoned mines (mine waters) are distributed throughout the area, although the mine waters concentrate in and around the Schwarzwald.The present analyses show, that the major element composition of a particular water is determined by the type of surrounding rock (e.g., crystalline or sedimentary rocks) and the depth from which the water originates. For waters from crystalline rocks it is the origin of the water that determines whether the sample is Na–Cl dominant (deeper origin) or Ca–HCO₃ dominant (shallow origin). In contrast, compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite (Ca–HCO₃ dominant), halite (Na–Cl dominant) or gypsum (Ca–SO₄ dominant). Major element data alone cannot, therefore, be used to trace the origin of a water. However, the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid–rock interaction processes. Accordingly, trace element analyses showed, that:

• −Ce anomalies can be used as an indicator for the origin of a water. Whereas surface waters have negative or strongly negative Ce anomalies, waters originating from greater depths show no or only weak negative Ce anomalies.
• −Eu anomalies can be used to differentiate between host rocks. Waters from gneisses display positive Eu anomalies, whereas waters from granites have negative ones. Waters from sedimentary rocks do not display any Eu anomalies.
• −Rb and Cs can also be indicators for the rock with which the fluid interacted: Rb and Cs correlate positively in most waters with Rb/Cs ratios of ∼2, which suggests that these waters are in equilibrium with the clay minerals in the rocks. Rb/Cs ratios >5 indicate reaction of a water with existing clay minerals, whereas Rb/Cs ratios <2 are probably related to host rock alteration and clay mineral formation.

The chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements (REEs), Rb and Cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements.     

某铁路隧道底鼓段粉砂质泥岩微宏观物理力学特性研究

西南地区YD隧道在运营期间隧道底部多段发生隆起变形,造成无砟轨道板开裂,导致轨道结构受损不稳定,影响行车安全。为了探明其底鼓原因,现对底鼓段紫红色缓倾层状粉砂质泥岩进行微宏观工程特性研究,分析其对隧道底鼓的影响。采用室内试验的方法,对该处粉砂质泥岩的物质组成成分、微观结构、膨胀性、抗剪抗压强度、压缩变形等围岩性质开展全面试验,并对围岩地应力、水文地质条件进行现场调查。试验和调查结果表明:研究区围岩根据岩石质量评价标准可以判定为Ⅳ级围岩;其岩石成分主要为伊利石、石英、绿泥石等,不含蒙脱石这种膨胀性黏土矿物,自由膨胀率最大为1.96%,不具备膨胀性;岩石的层理面上分布有2~8 μm大小的孔隙,岩石内部存在长度为3~8 μm的原生裂纹;岩石的单轴饱和抗压强度为11.3~21.8 MPa,属于较软岩;岩石的物理力学参数受含水量的影响较大,随着含水量的增加,内聚力缩减50%,抗压强度缩减了45%~55%,弹性模量缩减了50%。研究结果显示研究区岩体在水理作用下岩石强度会大幅度降低,但不含膨胀性矿物,不具备膨胀性。且根据现场监测,地下水位无变化,因此地下水和膨胀性不是隧道底鼓的直接诱因。     

碾子山晶洞碱性花岗岩矿物-水氧同位素交换反应动力学

对黑龙江碾子山碱性花岗岩的全岩及其主要单矿物进行了氧同位素分析，结果表明，全岩和单矿物不仅δ^18O 值变化范围较大（全岩－2．4－2．0‰，石英0．0－5．8‰，碱性长石－3．8－0．1‰，磁铁矿－8．5－1．0‰），而且强烈亏损^18O。共生矿物之间表现出明显不平衡的氧同位素分馏特征，指示在花岗岩侵位之后与水之间发生了同位素交换，根据锆石和现代大气降水的氧同位素组成，对岩石与外来流体的δ^18O值进行了估计，多维矿水－岩反应时限约为0．3－3Ma，水／岩比（氧摩尔比）介于0．11－1．02之间。水－岩反应温度较高（约400度）和反应时间较长是导致石英δ^18O值降低的主要原因。     

Provenance and Palaeoweathering Attributes of Proterozoic Rock Formations from the Son Valley,Central India

The characteristics of source rocks and weathering of Palaeoproterozoic phyllitic rock of Mahakoshal Group and Mesoproterozoic shales and siliciclastics of Vindhyan Supergroup exposed in Son Valley, Central India have been investigated by analyzing their chemical compositions. The investigations pertaining to the relationship between major-elements were carried out along Parshoi, Chitrangi, and Markundi areas of Son valley, Central, India. The studied rock strata have been classified into three categories namely phyllitic rocks, shales and sandstone.The A-CN-K ternary diagram, CIW, CIA, MIA, and ICV values indicate about the similar provenance or source rocks subjected to severe chemical weathering, under dry and hot-humid climates in a basic and acidic environment with changing lower to higher PCO₂ of continental flora. Various geochemical discriminantts diagrams, elemental ratios suggest that rocks are derived from post-Archaean-Proterozoic igneous source. The igneous source was mainly granite with a minor contribution of granodioritic rock, in a passive margin setting. The sediments responsible for formation of shale and sandstones were most likely deposited in the interglacial period in between the Mesoproterozoic and Neoproterozoic glacial times. Compositionally the sandstones is distinctive of cratonic environments with their passive continental margin setting. However, the phyllities of Mahakoshal Group suggests their formation under lower weathering conditions in dry climatic conditions which were operating on more intermediate to basic igneous rocks with abundance of mafic minerals.