缝合线研究的新进展——以湖北大冶铁山地区为例

为深入研究碳酸盐岩中的压溶作用,加深对压溶作用的认识和理解,以常见的缝合线构造为例,结合前人的研究成果和现代科技手段对湖北大冶铁山地区的缝合线构造进行了全面深入的研究,得到以下研究成果:丰富了缝合线类型;结合计算机技术获得了缝合线的三维形态;总结了缝合线形成中的一些主控因素;论述缝合线在应力分析、应变测量等传统领域及在能源资源等新领域的应用;对缝合线研究中存在的问题及分歧进行了评述并指出今后几年的研究重点。认为缝合线构造其实是一种不规则的压溶曲面;缝合线的形成是各种主控因素相互间复杂作用的结果;有关各主控因素的作用地位和特点方面的研究结果又可以为缝合线构造的实际应用提供理论依据。     

缝合线成因新认识

传统观点认为,碳酸盐岩中的缝合线是在岩石负载或构造应力作用下压溶形成的,是一种化学压实作用的产物。对缝合线进行综合研究,发现其具有“四性特征”,即完整性、亲烃性、排孔性及胀裂汇聚性。综合以上“四性”认为,缝合线主要是岩石在负重或构造应力作用下烃类（或泥质）使岩石发生胀裂形成的一种锯齿状裂缝,是烃类（或泥质）开辟的排烃通道,压溶作用对缝合线的贡献还有待研究。与碳酸盐岩相比,泥岩不发育缝合线,主要在于泥岩优势孔隙半径较大,烃类可以通过微孔以渗透方式向外排放,不需要形成缝合线。通过缝合线形成机理探讨,查明了碳酸盐岩与泥岩排烃方式的区别,进而对碳酸盐岩与泥岩封盖性进行对比。     

压溶角砾岩及其与铀成矿的关系

压溶角砾岩出现征构造带的较深部位并与构造角砾岩伴生,它是碳酸盐岩石构造破碎的一种特殊型式。压溶角砾岩由不同方向的缝合线发育而成,胶结物主要是碳酸盐岩的不溶残余物。碳酸盐岩中的铀含量主要与不溶残余物有关。在压溶作用发育过程中,岩层中的铀被活化、渗滤,在有利的物化环境中被炭、泥等吸附而富集,也可与其它成矿作用叠加而成矿。     

影像云纹法及GIS在缝合线三维重构中的应用

利用影像云纹法和GIS恢复了天然缝合线的三维形态,通过结果与标本的对比分析,证明了此套技术在实验室小构造分析中的实用性.通过处理缝合面的高程文件得到了各种形态的二维数字剖面,这些剖面更加全面地反映了标本的二维形态信息,且与天然缝合线的相似性较大.基于三维数字信息可以提取各种缝合线特征数据,如沟谷密度、搬运量大小、粗糙度等,这些数据可以反映缝合线在形成过程中的应力状况及物质迁移情况.     

碳酸盐岩压溶埋藏史和排烃数值模拟模型初步探讨

压溶作用产生的缝合线是烃富集的场所及初次运移的通道。碳酸盐岩烃源岩压溶过程,随着地层厚度和体积的减小,未熟和低熟油气会伴随孔隙流体一同排出。根据碳酸盐岩埋藏与压溶机理,提出了压溶的碳酸盐岩缝合线或溶解缝厚度恢复及其古厚度恢复的数学模型,同时结合碳酸盐岩基质和缝合线孔度随深度的变化曲线建立了定量计算碳酸盐烃源岩压溶排烃量的数学模型。上述数学模型的关键是确定压溶作用开始和结束的深度和时间,缝合线的厚度     

北特鲁瓦油田缝合线分布特征及主控因素分析

正缝合线是在地层上覆压力的作用下,接触的沉积物颗粒间发生选择性溶解而形成的裂缝,可形成于从沉积成岩到深埋的各个阶段。缝合线可以发育于各种岩性中,在碳酸盐岩储层中发育十分普遍,是碳酸盐岩储层中常见的地质构造。前人对缝合线的研究主要集中在成因、缝合线分类、物质组成、缝合线几何形状的定量化分析、地层压溶损失以及对于油气地质的意义等方面,极少对控制缝合线分     

运用显微构造分析方法讨论西秦岭某铀矿床矿化活动的构造环境

本文运用显微构造分析方法,讨论成岩期后铀矿化活动的构造环境。文中指出:矿化活动的首要条件是构造扰动;铀源质量改善和其后的叠加富集是矿化过程中的两次重要事件;吸附着铀的炭经构造重结晶作用从晶体中排出,从而改善了铀源质量;获释的炭和铀沿张性、张扭性裂隙聚集形成矿体;构造的作用在于提供了改变铀源的动力条件和矿化富集的空间场所。 方解石变形双晶、压溶缝合线等显微构造分析结果,一致表明区内引起变形的主应力近于水平。由压溶和重结晶前后矿物总表面积的变化推算的矿物表面能的变化为0.133J/cm3,以衡量应力强度。由动态重结晶颗粒粒度法估算的贮存着矿体的断裂的差异应力(σ_1-σ_3)为24—51MPa,且铀量随差异应力的增大而增加。     

碳酸盐岩中的压溶组构及其研究意义——以陕南—川北地区二叠—三叠系碳酸盐岩为例

<正> 压溶作用是碳酸盐沉积物在成岩作用阶段始终都存在的极为重要的作用。碳酸盐沉积物(岩)经压溶作用所产生的组构,最常见的是缝合线,此外还有羽状晶(压力影)、“角砾”、“瘤状”、“层纹”等构造。本文拟通过对陕南—川北地区二叠—三叠系碳酸盐岩中压溶组构的野外观察和室内鉴定工作,对压溶作用在碳酸盐岩中所产生的一些组构特征及其与原生组构的区别加以综合论述。     

缝合线形成的条件

缝合线是碳酸盐岩中又常见又醒目的一种构造。它的成因有很多假说,流行的是压溶说。笔者重点观察研究了华蓥山煤田和南桐煤田二叠系、三叠系灰岩的缝合线。 1.线合线成因缝合线主要由围岩、缝合面、缝合膜三要素组成。围岩是缝合线两侧的岩石;缝合面是围岩溶解凹凸不平的复杂面;缝合膜是由围岩溶解残留物在线合面上聚集压实而成的薄膜。围岩与缝合膜的矿物成分对比如表1。     

藏北羌塘盆地羌资5井二叠系碳酸盐岩储层特征及影响因素

羌资5井位于藏北羌塘盆地,该井钻遇二叠系龙格组及展金组。储层主要是龙格组及展金组中的碳酸盐岩,其主要岩性是微晶灰岩、粒屑灰岩、生物屑灰岩、角砾灰岩以及粉/细晶白云岩。储集空间主要为孔隙,另发育裂缝。孔隙可分为粒间孔、粒间溶孔、粒内溶孔、晶间孔及晶间溶孔、沿缝合线发育的溶孔;裂缝可分为构造缝、压溶缝和溶蚀缝。物性数据显示,孔隙度变化范围在0.3%~2.3%,平均值为1.31%;渗透率变化范围在(0.0034~0.0062)×10-3μm2,平均值为0.0044×10-3μm2,储层评价为差。影响碳酸盐岩储集物性的因素主要是成岩作用和构造作用。有利成岩作用主要是压溶作用、溶蚀作用、白云石化作用;不利的影响因素是压实作用、胶结作用、重结晶作用、硅化作用等。     

鲁西古生代碳酸盐岩中的垂直缝合线及其在华北板块构造演化中的意义

笔者在山东省淄博市博山区中奥陶统马家沟群白云岩和上石炭统本溪组石灰岩中识别出垂直缝合线。垂直缝合线都借助于平面X剪节理发育,缝合面上的“牙齿”与缝合面本身多呈斜交状态,其延伸方向代表着变形期最大主压应力轴（σ1）方向。根据垂直缝合面“牙齿”的突出方向判别：以山东博山地区为代表的华北东部地区在古生代中期和末期先后两次受到NNE—SSW方向的水平挤压作用。其中第一次挤压事件与遍布华北东部的中奥陶统—上石炭统（C2—O2）平行不整合抬升相关,而第二次则与华北东部古生代末期的褶皱隆起相联系。本文的研究为垂直缝合线在盆地构造演化研究中的应用提供了良好的研究实例。     

Compaction-formed platy limestone from the Middle Cambrian Zhangxia Formation (Western Hills,China): towards a new classification for bedded limestone

Remarkable bedding features occur in Middle Cambrian platy limestone of the Western Hills close to Beijing in NE-China, which are intercalated in a sequence of shallow water carbonates (mudstones, storm deposits, oolitic grainstones). The platy limestone beds (up to 5 cm thickness) have undergone complex diagenetic compaction and pressure solution. Varying facies types are characterized by wavy, stylolitic boundaries with different thickness of clay accumulation and common lateral pinch out. Cross-cutting relationships of stylolites commonly destroy primary bed-surfaces. This indicates an intimate interfingering resulting in an indenting fabric of primary separated facies types. Nevertheless, primary sedimentary boundaries can be recognized. There occur varying types of compaction features documented by different stylolite types with varying amplitudes and thickness of clay-enrichments (parallel clay seams, stylolamination, stylo-nodular and stylo-brecciated structures with multi-grained seams). Bedded limestone of the type documented, generally belong to the limestone family of Plattenkalk, Lithographic Limestone or platy limestone, which can form in different environments. Consequently, using these names without detailed data on some specific parameters (e.g. thickness, surface morphology, composition of allochems, particle and crystal size) results in more confusion and hinders the comparison of Plattenkalk, Lithographic Limestone and platy limestone from different locations throughout the earth history. Therefore, a classification is proposed here which is based on macroscopic, microscopic, and sub-microscopic parameters. Plattenkalk and platy limestone are considered to form the two main groups. Plattenkalk beds are laterally consistent and have parallel, horizontal surfaces. Platy limestone can pinch out laterally and reveals irregular and inclined bed surfaces. Single beds in both can have different thickness, internal structure (e.g. micritic, microsparitic) and fabric (e.g. homogeneous, nodular), particle content and other variations (e.g. chemical, mineralogical). These parameters should be added to the basic name and used in a system similar to Folk’s limestone classification. Lithographic Limestone is defined as a subgroup of Plattenkalk with well-defined parameters. A consequent use of this classification will also help to understand fossil preservation and/or non-preservation in different types of Plattenkalk, Lithographic Limestone, and platy limestone.     

塔河地区鹰山组灰岩白云石化成因及其对储层的影响

白云石化是碳酸盐典型的成岩作用类型之一,中-下奥陶统鹰山组浅海碳酸盐岩是塔河地区重要的含油气储层,普遍发育多种类型的白云石化作用。本文针对塔河地区鹰山组灰岩中沿缝合线分布这一特定类型的白云石化进行了研究。岩石学基础上的阴极发光分析、⁸⁶Sr/⁸⁷Sr比值以及δ¹³C-δ¹⁸O 的研究表明,这种类型的白云石化发育于相对还原的浅埋藏成岩环境,孔隙中的残留海水是主要的白云石化流体来源,碳酸盐矿物(主要是高镁方解石)稳定化过程中释放的Mg²⁺ 可能是白云石化主要的物质来源,而埋藏过程中逐渐升高的温度一定程度上也促进了白云石化的发生。成岩流体及Mg²⁺ 有限的供给量限制了白云石化作用的整体规模。显微结构与岩石物性分析表明,该类白云石化对储层物性参数的绝对贡献相对有限,但可能成为小规模油气运移以及深部热流体活动的潜在通道。     

石灰岩裂隙摩擦强度愈合的压力溶解和应力腐蚀模型研究

为模拟试验中观察到的石灰岩裂隙摩擦强度愈合现象,提出用压力溶解和应力腐蚀相结合的综合模型来模拟裂隙摩擦强度的愈合。综合模型可同时考虑压力溶解和应力腐蚀对裂隙接触面的改造作用,通过裂隙接触面积的变化表征摩擦强度的愈合。模拟结果表明：压力溶解模型低估了短控制时间内摩擦强度的愈合量,通过进一步的参数敏感性分析发现,随着控制时间的增长,温度的升高显著地提高了压力溶解模型的模拟值,而有效应力的增加对模拟值的影响相对较小;应力腐蚀模型则主要反映应力压缩引起的裂隙接触面积增长;压力溶解模型和应力腐蚀模型结合则能较好地模拟裂隙摩擦强度的愈合。因此,用压力溶解模型模拟裂隙摩擦强度愈合时,特别是在模拟短控制时间内和低温条件下力学占主导作用的愈合时,应考虑应力腐蚀引起的裂隙接触面积变化。     

The Development of Stylolites in Carbonate Formation: Implication for CO2 Sequestration

The impact of CO2 sequestration on the host formation is an issue occurring over geologic time. Laboratory tests can provide important results to investigate this matter but have limitations due to a relatively short timeline. Based on literature review and core sample observation, naturally occurred geological phenomena, stylolites are studied in this paper for understanding CO2 sequestration in deep carbonate formations. Stylolites are distinctive and pervasive structures in carbonates that are related to water-assisted pressure solution. Pressure solution involving stylolitization is thought to be the main mechanism of compaction and cementation for many carbonates. In parallel, CO2 sequestration in carbonate formation involves extensive chemical reactions among water, CO2 and rock matrix, favoring chemical compaction as a consequence. An analogue between stylolites and CO2 sequestration induced formation heterogeneity exists in the sense of chemical compaction, as both pressure solution in stylolites and CO2 enriched solution in CO2 sequestration in carbonate formations may all introduce abnormal porous regions. The shear and/or tension fractures associated with stylolites zones may develop vertically or sub-vertically; all these give us alert for long-term safety of CO2 sequestration. Thus a study of stylolites will help to understand the CO2 sequestration in deep carbonate formation in the long run.     

Strain partitioning and deformation mode analysis of the normal faults at Red Mountain, Birmingham, Alabama

In a low-temperature environment, the thin-section scale rock-deformation mode is primarily a function of confining pressure and total strain at geological strain rates. A deformation mode diagram is constructed from published experimental data by plotting the deformation mode on a graph of total strain versus the confining pressure. Four deformation modes are shown on the diagram: extensional fracturing, mesoscopic faulting, incipient faulting, and uniform flow. By determining the total strain and the deformation mode of a naturally deformed sample, the confining pressure and hence the depth at which the rock was deformed can be evaluated. The method is applied to normal faults exposed on the gently dipping southeast limb of the Birmingham anticlinorium in the Red Mountain expressway cut in Birmingham, Alabama. Samples of the Ordovician Chickamauga Limestone within and adjacent to the faults contain brittle structures, including mesoscopic faults and veins, and ductile deformation features including calcite twins, intergranular and transgranular pressure solution, and deformed burrows. During compaction, a vertical shortening of about 45 to 80% in shale is indicated by deformed burrows and relative compaction of shale to burrows, about 6% in limestone by stylolites. The normal faults formed after the Ordovician rocks were consolidated because the faults and associated veins truncate the deformed burrows and stylolites, which truncate the calcite cement. A total strain of 2.0% was caused by mesoscopic faults during normal faulting. A later homogenous deformation, indicated by the calcite twins in veins, cement and fossil fragments, has its major principal shortening strain in the dip direction at a low angle (about 22°) to bedding. The strain magnitude is about 2.6%. By locating the observed data on the deformation mode diagram, it is found that the normal faulting characterized by brittle deformation occurred under low confining pressure (< 18 MPa) at shallow depth (< 800 m), and the homogenous horizontal compression characterized by uniform flow occurred under higher confining pressure (at least 60 MPa) at greater depth (> 2.5 km).     

藏北羌塘盆地羌资2井中侏罗统布曲组碳酸盐岩岩石学及储集物性特征

本文讨论了羌塘盆地羌资2井中侏罗统布曲组碳酸盐岩岩石学及储集物性特征。碳酸盐岩主要有亮晶鲕粒灰岩、白云岩、泥晶灰岩, 以及他们之间的过渡类型; 储集空间主要有孔隙与裂缝两种类型, 表现为孔隙—裂缝组合。孔隙可分为粒间溶孔、粒内溶孔、晶间孔、晶间溶孔、沿缝合线等分布的溶孔; 裂缝可 分为构造缝、构造—溶解缝、压溶缝和溶蚀缝。亮晶鲕粒灰岩孔隙度平均值1.084%, 渗透率平均值0.0319× 10-3 mm2; 白云岩孔隙度平均值1.77%, 渗透率平均值0.1591×10-3 mm2; 储集物性特征均为低孔低渗、高排替压力、微-细喉道、分选中等-不好的负偏态细歪度特征。泥晶灰岩和过渡类型灰岩的储集物性特征与亮晶鲕粒灰岩和白云岩相似。最后, 讨论了成岩作用对碳酸盐岩储集物性的影响, 并认为成岩作用对储集物性的不利影响明显大于有利影响。     

全球奥陶系碳酸盐岩油气藏综述

奥陶系碳酸盐岩油气田主要分布于北美、北欧、中国和澳大利亚。在北美,油气藏主要分布于下奥陶统El-lenburger组选择性白云岩化和经喀斯特改造的碳酸盐岩层系中;上奥陶统的Trenton-Black River灰岩,特别是Trenton灰岩段的构造破碎和白云岩化作用是影响油气成藏的主控因素;Red River组油藏则受控于构造圈闭。北欧哥特兰岛Klasen灰岩储集空间则以灰泥丘原生孔隙和断裂、缝合线为主。中国奥陶系油气藏分布于鄂尔多斯盆地和塔里木盆地,成藏条件相对复杂:在鄂尔多斯盆地,主要与膏云岩经大气淡水淋滤作用形成的风化壳密切相关,也有白云岩、生物礁等多种储集体;而塔里木盆地塔中地区储集体集中于礁滩相,还包括台地灰岩和台缘浅滩白云岩等其他相带,沉积间断面上的古喀斯特作用是成藏的主控因素。澳大利亚的坎宁盆地是较新的勘探区,其油气聚集方式与北美Ellenburger组相似。     

水化学溶液下灰岩力学特性及神经网络模拟研究

基于水化学溶液浸泡的饱和灰岩三轴压缩试验结果,分析了影响灰岩变形及强度等力学特性的主要因素,认为随溶液酸碱度增加,弹性模量及峰值强度均有降低的趋势;相同pH值,Na2SO4溶液、蒸馏水和CaCl2溶液对灰岩强度的弱化程度依次降低;随着围压的增加,岩石强度逐渐增大,岩石到达峰值强度时的轴向变形也越来越大,塑性变形明显增加。考虑应力路径和化学溶液的影响,利用遗传算法优化神经网络结构,建立了进化神经网络本构模型。通过样本学习模型能较好地描述化学环境下灰岩的力学性能,5种不同化学环境下的力学试验验证了进化神经网络模型模拟结果的可靠性,该方法可以推广到化学环境下其他岩石的力学试验模拟。