岩石断裂作用的复杂性和混沌动力学

断裂是一个复杂的动力学体系,受到岩石结构、反应、流体迁移、应力、岩石变形和力学等多种地质因素和过程的耦合控制。本文建立了断裂体系的反应-输运-力学耦合动力学模型并编制了模拟程序。以湖南水口山矿区为例,通过动力学模拟表明不同地层岩性的断裂渗透率大小和演化特征存在显著差异,断裂作用促使岩石渗透率的空间非均匀性增强,从而有利于流体的局部汇聚和矿体的形成。断裂中压力随时间呈现出非周期振荡变化,反映了断裂演化的混沌特征。     

构造-流体-成矿体系的反应-输运-力学耦合模型和动力学模拟

建立了一个综合的构造流体成矿体系的反应输运力学耦合动力学模型。利用有限元方法求解岩石变形、断裂作用和断裂网络统计动力学、流体流动、有机和无机地球化学反应及成岩成矿作用、压力溶液和其它压实力学、热迁移的方程组 ,可以对构造流体成矿体系的动力学演化过程进行 1～ 3维数值模拟。模拟的主要内容是在各种过程耦合作用下描述构造流体成矿体系的主要变量的时空演化 :( 1)与成矿流体的形成和性质有关的变量 ,如地层中矿物 (包括成矿物质 )的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等 ;( 2 )与构造变形和流体运移有关的各变量 ,如应力与变形速率、岩石孔隙度、构造 (断裂 )渗透率等 ;( 3 )与沉淀成矿有关的变量 ,如矿物 (金属矿物和脉石矿物 )的成核速率、各矿物的沉淀量等 ;( 4 )上述各有关变量间的时空耦合关系 ,如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。以湖南沃溪金锑钨矿床为例 ,应用该模型和方法对成矿动力学过程和动力学机制进行了初步的模拟与分析。     

北方岩溶区断裂带水文地质性质及结构模型

断层带结构和内部流体流动特性是水文地质研究领域的难点问题。石油地质领域,在油气运移与成藏方向已形成较成熟的断层封闭性定量评价技术手段。相比较,断裂的水文地质性质研究尚停留在断裂的力学性质对断层导水、阻水特性的定性评价阶段,尚未详细开展断裂带结构、渗透性各向异性等方面的研究工作。文章梳理总结国外断裂带水文地质性质研究中关于结构组成、断裂带演化、渗透率影响因素等方面的研究成果,引入断裂带渗透率结构模型,并以中国北方岩溶区碳酸盐岩与碎屑岩互层含水岩组为例,构建断裂带水文地质结构模型。断裂带研究尺度和精度不同、断裂带发育部位不同,导致其结构及水文地质性质亦不相同,如何建立起精确、典型的断裂带水文地质结构模型,需要各领域数据共享及多学科融合共同开展研究工作。      

Influence of host lithofacies on fault rock variation in carbonate fault zones: A case study from the Island of Malta

Relatively few studies have examined fault rock microstructures in carbonates. Understanding fault core production helps predict the hydraulic behaviour of faults and the potential for reservoir compartmentalisation. Normal faults on Malta, ranging from <1 m to 90 m displacement, cut two carbonate lithofacies, micrite-dominated and grain-dominated carbonates, allowing the investigation of fault rock evolution with increasing displacement in differing lithofacies. Lithological heterogeneity leads to a variety of deformation mechanisms. Nine different fault rock types have been identified, with a range of deformation microstructures along an individual slip surface. The deformation style, and hence type of fault rock produced, is a function of host rock texture, specifically grain size and sorting, porosity and uniaxial compressive strength. Homogeneously fine-grained micrtie-dominated carbonates are characterised by dispersed deformation with large fracture networks that develop into breccias. Alternatively, this lithofacies is commonly recrystallised. In contrast, in the coarse-grained, heterogeneous grain-dominated carbonates the development of faulting is characterised by localised deformation, creating protocataclasite and cataclasite fault rocks. Cementation also occurs within some grain-dominated carbonates close to and on slip surfaces. Fault rock variation is a function of displacement as well as juxtaposed lithofacies. An increase in fault rock variability is observed at higher displacements, potentially creating a more transmissible fault, which opposes what may be expected in siliciclastic and crystalline faults. Significant heterogeneity in the fault rock types formed is likely to create variable permeability along fault-strike, potentially allowing across-fault fluid flow. However, areas with homogeneous fault rocks may generate barriers to fluid flow.     

构造成矿非线性动力学:2.湘西金矿研究实例

应用递增应力流变学方法对湘西沃溪金矿成矿过程中构造变形、应力、流体流动、地球化学反应及成岩成矿作用等多过程间的耦合作用和非线性特征进行了模拟和分析。构造压溶作用对矿源层中成矿物质的溶解与迁移起了重要作用。断裂作用可以产生比原岩渗透率高近4个数量级的断裂渗透率,从而促进流体的流动、组分扩散和在断裂中的汇聚成矿。不同岩性对断裂作用和断裂渗透率的演化有重要影响,并且构造、流体、岩石之间存在强烈的非线性耦合作用,马底驿组中段是最有利的构造成矿层位。     

断层内部结构及其对封闭性的影响

先前的研究多考虑断层封堵和开启的2种极端状态,近来的研究认为,在多数情况下断层处于2种之间的状态,只有在静止期具有封闭能力的断层,才有可能对油气起封堵作用。分析断层对流体运移的影响,需要分析断层在演化过程中的内部结构特征。断层可以划分出破碎带、诱导裂缝带和围岩3部分,断层岩和伴生裂缝构成破碎带的主体部分。常见的断层岩包括断层角砾岩、断层泥和部分碎裂岩,它们充填在断层裂缝空间中,断层内部结构受断层形成时的构造应力性质、断层活动强度和围岩岩性因素的控制。从动态角度看,随着断距增加,断层活动伴随着裂缝的发育和岩石的破碎混杂,可用泥质源岩层厚度和断距的比值来划分不同的发育阶段。断层活动期为油气运移通道,在静止时表现出差异性的封闭,通常用断层渗透率和排替压力2个参数来定量评价断层的封闭程度。断层岩渗透率主要受断距、泥质含量、埋深等因素的控制;断层排替压力的预测方法有2种:一种是从断层岩成岩角度分析的"等效埋深法",另一种是分析实测排替压力与主控地质因素的"拟合法"。通过简化的断层模型,建立了渗透率、排替压力与主控因素的预测关系。和储层类似,流体在断层中的运移遵循多孔介质的渗流特征。利用断层两侧的流体压力和油气柱高度并不能直接评价封闭性能,还必须考虑油气充注史和流体压力变化历史。     

新疆阿尔泰地区断裂控矿的多重分形机理

新疆阿尔泰地区断裂构造非常发育并对热液成矿有重要控制作用。分形分析表明该区断裂和矿床的空间分布均为多重分形分布,断裂的奇异指数为1.597～2.403,多重分维谱值为0.551～1.706;矿床的奇异指数为0.925～2.287,分维谱值为0.138～1.363。断裂的高的奇异指数和分维谱值表明该区断裂构造具有较高的成熟度和连通性,有利于提高岩石渗透性、促进流体流动和热液矿床的形成。断裂构造的多重分形分布导致该区热液成矿作用的多重分形分布。断裂体系演化过程中不同断裂部位变形和渗透性存在明显差异,数值模拟表明断裂与岩性和流体之间存在强烈的耦合作用并导致不同岩性的断裂具有明显不同的断裂渗透率。断裂-脉体系演化是一个自组织过程,元胞自动机模拟表明只有在分形渗透临界以上连通性较好的脊骨断裂部位是最有利于流体流动和成矿作用的。因此只有在部分有利的断裂部位才能形成矿床,并导致了断裂构造的奇异指数和多重分维谱值明显高于矿床。     

含油气盆地分析中流体输导系统的研究

盆地分析研究中流体输导系统的研究是一个重要的方面。在沉积盆地中,烃类流体从源岩到圈闭的过程整个是一个动态的过程。因此,在进行流体导系统的研究时,必须考虑油气源岩、流体输导层、封闭层在时空上的配置关系,然后才能建立起流体输导系统的整体格架,论述了流体输导系统的研究流程,包括源岩分析、构造格架和断层的分析、水动力学的研究等,并进一步强调了动态分析的方法来研究流体输导系统的必要性。最后,给出了流体输导系     

断层破碎带突水突泥演化特征试验研究

为了研究富水断层破碎带隧道突水突泥灾害演化机制,自行研制了一套可考虑质量迁移及地应力状态的大型室内突水突泥试验系统。利用该装置开展了不同水压加载方式、不同破碎带介质参数等条件的断层破碎带突水突泥灾害演化过程模拟试验。结果表明：（1）断层破碎带突水突泥灾害演化是渗流?侵蚀强耦合过程,在水压作用下,破碎带介质中的细颗粒首先发生迁移,导致充填介质孔隙结构增加,进而加速细颗粒流失,促使涌水率不断增长,随着细颗粒不断迁移流失,水流流态由层流转换为紊流,最终诱发突水突泥灾害;（2）破碎带介质初始孔隙率和施加水压越大越易诱发突水突泥,介质渗流演化特征越明显,渗流场参量如渗透率、孔隙率、雷诺数增加越快,且渗流场参量演化曲线出现突增现象;（3）梯度水压加载模式下断层破碎带介质较恒定水压加载条件下突水突泥演化特征更明显,介质发生突水突泥的临界水压更小。在此基础上,基于涌水率?时间（Q-t）、水力梯度?涌水率（i-Q）关系的流态转换分析和基于渗透率?水力梯度（k-i）关系的渗透性演化特征,建立了断层破碎带渗透演化特征概化模型。该研究结果对于断层破碎带突水突泥灾害演化机制与防治措施具有一定的理论指导价值。     

Experimental Researches on Hydro-Mechanical Properties of Altered Rock Under Confining Pressures

Altered rock, as the abutment materials of Xiaowan Hydropower Station in China, is a kind of geological defective rock mass. It is loosely structured and its strength is low, with some development of pores and cavities. Research on the hydro-mechanical coupling of the altered rock are of important significance to hydropower projects. In this study, the advanced fully automatic triaxial fluid flow-rheological test servo system is employed to study the hydro-mechanical coupling characteristics of the altered rock, and the water pressures and confining pressures in the laboratory tests are set to simulate the conditions of excavation and impoundment of Xiaowan Hydropower Station. Based on the test results, the stress–strain laws of the rock specimens under the effect of complete hydro-mechanical coupling, as well as the lateral strain and volumetric strain characteristics, are studied. The fluid flow laws of the rock specimens and the effects of the confining pressures on the fluid flow are analyzed. The fluid flow failure characteristic under the effect of the complete hydro-mechanical coupling is discussed. The research achievements show that with the change of the stress states, the permeability of the rock also changes, and the permeability evolution shows the phase characteristic during the process of stress and strain. The impacts of the confining pressures on the strength and deformation and permeability of the altered rock are obvious. The failure behaviours of the rock specimens under the effect of coupling relates to the confining pressures, including two kinds of splitting failure and shear failure. The fluid flow failure characteristic of the rock specimens depend upon the initiation, growth and coalesce of micro-cracks, heterogeneity, confining pressures and properties of the rock.     

断裂在纯净砂岩中的变形机制及断裂带内部结构

以纯净砂岩为对象,考虑了影响断裂变形的主要因素,包括成岩阶段、孔隙度、温度和围压,系统剖析了不同性质砂岩的断裂变形机制、微构造特征及形成断裂带的内部结构,对研究砂岩内断裂封闭性具有重要的指导意义。研究表明：纯净的砂岩在未固结-半固结成岩阶段发生断裂,变形机制为颗粒边界摩擦滑动,导致颗粒旋转和滚动,即为颗粒流,形成的微构造为解聚带,孔渗性同母岩比没有明显降低,断裂带尽管具有断层核和破碎带二分结构,但渗透率比母岩高,为流体垂向运移的通道;在固结成岩阶段（孔隙度大于15%）发生断裂,变形机制为碎裂作用,颗粒边界摩擦滑动导致颗粒旋转,即为碎裂流,形成的微构造为碎裂带,渗透率同母岩比一般降低1～3个数量级,形成侧向有一定封闭能力、垂向渗透的断裂带;固结阶段（孔隙度小于15%）发生断裂,开始由于破裂作用,形成断层角砾岩,伴随着碎裂流发生,形成碎裂岩,因此早期形成高渗透断裂带,后期断层逐渐封闭。固结成岩的砂岩在抬升过程发生断裂,变形机制为破裂作用,形成无内聚力的角砾岩,为高渗透断裂带。在不同成岩阶段发生变形,形成多类型变形构造的叠加,对于一条晚期形成的断层而言,由于不同深度变形机制及微构造类型不同,导致油气选择性充注,碎裂带和压溶胶结碎裂带阻止油气向高孔隙度砂岩中充注,解聚带会成为油气运移的通道,裂缝有利于油气优先充注。因此,高孔隙性砂岩中孔隙度较低的储集层由于碎裂带不发育常常含油气性最好,而低孔隙性砂岩由于裂缝产生含油气性较好。     

The role of dewatering in the progressive deformation of a sandy accretionary wedge: constraints from direct imagings of fluid flow and void structure

Geological investigation of the deformation structures and sedimentary setting of the Emi Group, a Miocene sand-rich accretionary complex, central Japan, revealed a six stage-structural evolution during shallow level accretion in a subduction zone. The early deformation (stage 1) is characterized by independent particulate flow in layer parallel faults, scaly cleavages and web structures, and upward dewatering in dish-and-pillar structures and breccia injections, while later deformation (stages 2–6) involve mappable scale folding, meso- to macro-scopic thrusts and web structures with cataclastic flow. Based on microscopic analyses of these structures, the early faulting with independent particulate flow (stage 1 deformation) is associated with dilatancy and preferred orientation of void space, whereas the later faulting with cataclastic flow (stage 2 deformation) occurs with compaction and crude preferred orientation. The former features imply more permeable fluid migration pathways, supported by the permeability measurements and direct imaging of fluid flow by X-ray CT. On the other hand, the later fault zone has lower permeability and porosity than intact rock, and plays as fluid sealing. Thus, in the early stage (stages 1), fluid flow occurs as focused flow through dilatant fault zones with independent particulate flow or fluid migration by upward dewatering forming dish-and-pillar structures and breccia injections, whereas no evidence of fluid flow is recognized at the later stages (stages 2–6). Namely the fault zones focus fluid flow during primary accretion in shallow levels, and the fluid flow is strongly controlled by the deformation mechanism. Furthermore, the change of the deformation mechanism could be effected by progressive increment of the confining pressure, accompanied with accretion and lithification in the accretionary prism. In the shallow, dilatant-faulting regime where the deformation mechanism is independent particulate flow, focused flow dominates, whereas in the deep, cataclastic regime distributed flow may play a main conduit rather than the focused flow.     

碳酸盐岩内断裂带结构及其与油气成藏

以野外观察描述为手段,系统研究了碳酸盐岩断裂变形机制的影响因素及断裂带结构演化过程,剖析了碳酸盐岩地层中断裂带结构与流体运移的关系。研究表明,影响碳酸盐岩内断裂变形机制的因素包括岩性、孔隙度、变形深度、温度、胶结作用、先存裂缝等,控制断裂带结构形成的因素包括滑动位移和破裂模式等。低孔隙度碳酸盐岩以裂缝发育为主,高孔隙度碳酸盐岩变形早期产生变形带,带内裂缝联接逐渐发育成断层带。随着埋藏深度的增加,断裂带结构不同：埋藏深度小于3 km,断层核主要发育无内聚力的断层角砾岩和断层泥;埋藏深度大于3 km,断层核普遍发育有内聚力的断层角砾岩和碎裂岩,破碎带发育多种成因的裂缝。随着位移的增加,破裂模式从早期的破裂作用变为后期的碎裂作用,最终形成碎裂流。断裂带演化是一个四维过程,断层核和破碎带发育情况直接影响断层对油气的运移和封闭的作用。断裂变形机制、断裂带内部结构以及与流体运移关系的研究,都可为封闭性提供重要的理论依据。     

构造成矿非线性动力学:1.递增应力流变学模型

本文提出了构造成矿作用动力学研究的递增应力流变学方法。利用该方法将构造变形、应力、流体流动、地球化学反应及成岩成矿作用等多过程耦合起来，可以从多种地质过程的耦合与反馈作用对构造成矿的动力学演化过程进行１～３维数值模拟。模拟的主要内容是在各种过程耦合作用下，以下描述构造成矿体系的主要变量的时空演化：（１）与成矿流体的形成和性质有关的变量，如地层中矿物（包括成矿物质）的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等；（２）与构造变形和流体运移有关的各变量，如应力与变形速率、岩石孔隙度、构造（断裂）渗透率等；（３）与沉淀成矿有关的变量，如矿物（金瞩矿物和脉石矿物）的成核速率、各矿物的沉淀量等；（４）上述各有关变量间的时空耦合关系，如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。     

采动煤岩渗透率演化模型及数值模拟

为描述采动煤岩渗透率演化过程,引入强度退化指数,基于Hoek-Brown强度准则,建立了考虑围压影响的煤岩应变软化力学本构模型。给出了体积应变和渗透率的关系方程,结合应变软化模型建立了采动煤岩渗透率演化模型,并在FLAC下予以实现。通过数值模拟研究了不同围压下圆柱岩样的峰后应变软化力学行为和某煤矿工作面开采过程中煤岩的渗透率演化过程,结果表明：（1）该模型能较好地反映围压对煤岩峰后应变软化行为的影响;（2）随着工作面推进,越来越多的煤岩单元破坏,渗透率也不断增长,逐渐成为瓦斯等流体运移的主要通道。（3）模型能再现采动煤岩渗透率演化的动态过程,从而为煤与瓦斯共采、煤层瓦斯抽放和瓦斯灾害防治提供指导。     

A numerical model simulating reactive transport and evolution of fracture permeability

A numerical model is presented to describe the evolution of fracture aperture (and related permeability) mediated by the competing chemical processes of pressure solution and free‐face dissolution/precipitation; pressure (dis)solution and precipitation effect net‐reduction in aperture and free‐face dissolution effects net‐increase. These processes are incorporated to examine coupled thermo‐hydro‐mechano‐chemo responses during a flow‐through experiment, and applied to reckon the effect of forced fluid injection within rock fractures at geothermal and petroleum sites. The model accommodates advection‐dominant transport systems by employing the Lagrangian–Eulerian method. This enables changes in aperture and solute concentration within a fracture to be followed with time for arbitrary driving effective stresses, fluid and rock temperatures, and fluid flow rates. This allows a systematic evaluation of evolving linked mechanical and chemical processes. Changes in fracture aperture and solute concentration tracked within a well‐constrained flow‐through test completed on a natural fracture in novaculite (Earth Planet. Sci. Lett. 2006, in press) are compared with the distributed parameter model. These results show relatively good agreement, excepting an enigmatic abrupt reduction in fracture aperture in the early experimental period, suggesting that other mechanisms such as mechanical creep and clogging induced by unanticipated local precipitation need to be quantified and incorporated. The model is applied to examine the evolution in fracture permeability for different inlet conditions, including localized (rather than distributed) injection. Predictions show the evolution of preferential flow paths driven by dissolution, and also define the sense of permeability evolution at field scale. Copyright © 2006 John Wiley & Sons, Ltd.     

Dissimilar properties within a carbonate-reservoir's small fault zone,and their impact on the pressurization and leakage associated with CO2 injection

This paper focuses on a small fault zone (too small to be detected by geophysical imaging) affecting a carbonate reservoir composed of porous and low-porosity layers. In a gallery located at 250 m depth, the hydraulic properties of a 20 m thick section of the reservoir affected by the studied fault are characterized by structural measurements and hydraulic injection into boreholes. We conducted electrical tomographies before and after an 18 hour-long injection, to image the fluid flow through the fault zone. Our main finding is that the damage zone displays contrasting permeability values (up to two orders of magnitude) inherited from the differential alteration of the intact rock layers. To characterize the impact of these hydraulic-property variations on the fluid flow, we carried out numerical simulations of water and supercritical CO₂ injections, using the TOUGH2 code. Two damage-zone models were compared, with heterogeneous (Model 1) and homogeneous (Model 2) hydraulic properties. In Model 1, injected fluids cannot escape through the fault zone; they generate a high fluid overpressure, located in the damage-zone layers having the highest permeability and storativity. In Model 2, fluids can easily migrate; the overpressure is lower and located in the host rock along the fault zone.     

Review and classification of structural controls on fluid flow during regional metamorphism

Mechanisms for kilometre-scale, open-system fluid flow during regional metamorphism remain problematic. Debate also continues over the degree of fluid flow channellization during regional metamorphism, and the mechanisms for pervasive fluid flow at depth. The requirements for pervasive long-distance fluid flow are an interconnected porosity and a large regional gradient in fluid pressure and hydraulic head (thermally or structurally controlled) that dominates over local perturbations in hydraulic head due to deformation. In contrast, dynamic or transient porosity interconnection and fluid flow accompanying deformation of heterogeneous rock suites should result in moderately to strongly channellized flow at a range of scales, of which there are many examples in the literature. Classification of fluid flow types based on scale and degree of equilibration between fluid and rock, wallrock permeability, and mode of fluid transport contributes to an understanding of key factors that control fluid flow. Closed-system fluid behaviour, with restricted fluid flow in microcracks or cracks and limited fluid–rock interaction, occurs over a range of strains and crustal depths, but requires low permeabilities and/or small fluid fluxes. Long-distance, open-system fluid flow in channels is favoured in heterogeneous rocks at high strains, moderate (but variable) permeabilities, and moderate to high fluid fluxes. Long-distance, broad, pervasive fluid flow during regional metamorphism requires that the rocks are not accumulating high strains and have high permeabilities, low permeability contrasts, and high fluid fluxes. The ideal situation for such fluid flow is in situations where the rocks are undergoing stress relaxation immediately after a major deformation phase. In the mid-crust, fairly specific conditions are thus required for pervasive fluid flow. During active orogenesis, structurally controlled fluid flow (with focused open systems surrounding regions of closed-system behaviour) predominates in most, but not all, regional metamorphic situations, at a range of scales.     

流体输运,化学反应与交代作用

在成矿及变质作用过程中， 体运移促使热量发生传输及周围岩石发生化学反应和交代作用。流体输过一化学反应耦合动力学方程能定量评价热液系统组分浓度、温度和流量函数的人演化，对于区域变质和交代韧性断裂带等变质系统，还可通过流体运称方向和时间积分流体能量来定量描述流体输运一化学反应耦合客观变持地体中水力破裂的形成与流体运移和失挥发分反应耦合过程有关。     

Fracture analysis in the south-western Corinth rift (Greece) and implications on fault hydraulic behavior

This paper reviews the data concerning the fracture network and the hydraulic characteristics of faults in an active zone of the Gulf of Corinth. Pressure gap measured through fault planes shows that in this area the active normal faults (Aigion, Helike) act, at least temporarily and locally, as transversal seal. The analysis of the carbonate cements in the fractures on both the hangingwall and the footwall of the faults also suggests that they have acted as local seals during the whole fault zone evolution. However, the pressure and the characteristics of the water samples measured in the wells indicate that meteoric water circulates from the highest part of the relief to the coast, which means it goes through the fault zones. Field quantitative analysis and core studies from the AIG-10 well have been performed to define both regional and fault-related fracture networks. Then laboratory thin section observations have been done to recognize the different fault rocks characterizing the fault zone components. These two kinds of approach give information on the permeability characteristics of the fault zone. To synthesize the data, a schematic conceptual 3D fluid flow modeling has been performed taking into account fault zone permeability architecture, sedimentation, fluid flow, fault vertical offset and meteoric water influx, as well as compaction water flow. This modeling allows us to fit all the data with a model where the fault segments act as a seal whereas the relays between these segments allow for the regional flow from the Peloponnese topographic highs to the coast.