鄂尔多斯盆地延安地区马五段上组合细粒白云岩储层特征及有利储层控制因素

针对鄂尔多斯盆地延安地区马五段上组合（马五4至马五1亚段） 细粒致密白云岩储层天然气勘探取得新突破,展开对 低孔低渗白云岩储层特征及孔隙的成因研究。通过岩心观察、薄片分析及阴极发光等测试,结合岩石物性分析,明确了细 粒白云岩储层的储渗特征、有利储层的演化过程及控制因素。结合地球化学及地球物理数据分析认为,研究区马五段上组 合储层岩性主要包括含膏模白云岩、细晶白云岩和岩溶角砾岩等,储集空间以膏模溶孔、晶间（溶） 孔、非选择性角砾间 溶蚀孔洞为主,局部裂缝发育,属低孔低渗孔隙型储集层;位于高古地势、经多期岩溶（准同生期、表生期和埋藏期岩 溶） 叠加改造的膏晶模云坪是研究区细粒白云岩有利储层的主要分布区。     

广西菜子岩剖面中上泥盆统界线附近沉积相与海平面变化*——兼论华南吉维期中期的海退及时间

广西菜子岩剖面处于台地边缘地带,含有底栖生物及浮游生物化石。综合岩相、生物相等资料,按牙形石带时限讨论了该地区吉维期—弗拉斯期早期主要的海平面变化历史。吉维期早期(相当于东岗岭组)经历了持续的海侵,大致下varcus带末期可能出现短暂的海退;“谷闭组”下部岩性复杂,海平面波动强烈,其中较大规模的包括了发生于上varcus带的海退(即吉维期中期海退)及下hermanni-cristatus带初期的海侵。吉维期晚期地层含有丰富的床板珊瑚以及其他礁体生物碎屑,产层孔虫、海百合等,意味着这个时期研究区可能处于礁前的上斜坡部位。“谷闭组”上部（牙形石falsiovalis带至transitans带下部）的岩性为中—薄层与厚层的灰岩互层,以正常的底栖生物为主,反映了由原来的礁前到滩前的变化,但水体深度在中—晚泥盆世界线前后可能总体相似。融县组(底部)以浅灰、灰白色的中—薄层至厚层—块状灰岩为特征,其沉积始于牙形石transitans带中部,证据表明此时海水可能变深。菜子岩剖面的白云岩位于上varcus带的下部,主要为细—中晶结构,见有灰岩残余以及正常海相生物碎屑。横向上与其他剖面对比表明,广西地区上varcus带可能出现了区域性的海退事件。     

贵州赤水地区中三叠统雷口坡组的成岩作用和储集性

赤水地区中三叠统雷口坡组的气藏是１９９１年初发现的，其储层主要发育在雷一＾１中段。储集岩主要为溶孔粉晶云岩，储集空间为晶间孔、晶间溶孔及溶孔。受沉积环境控制，成岩早期的淡水溶蚀作用是形成储集性的主要原因，导致雷一＾１亚段的储层具明显的成层性，而印支期抬升引起的风化淋滤作用进一步改善了储集性。成岩期的石膏充填则是使储集空间遭破坏的主要因素。本文通过“四性研究”，充分利用岩石学、岩石地球化学及各种微电     

渤海湾盆地北塘凹陷古近系沙河街组三段白云岩中方沸石的特征及成因

渤海湾盆地北塘凹陷古近系沙河街组三段白云岩中有多种矿物,X射线衍射(XRD)分析识别出的主要矿物有白云石、方沸石、石英、长石、黏土矿物、黄铁矿及方解石等,其中方沸石平均含量达38.8%。根据钻井岩心、岩石薄片、扫描电镜、电子探针和地球化学分析等资料,对沙三段白云岩中方沸石的矿物特征进行详细描述并探究其成因。结果表明,沙三段白云岩中的方沸石有2种分布样式,分别是纹层型和充填型,其中前者多与白云石互层、呈纹层状,偶见似结核状;后者形成较晚,方沸石以填隙物形式充填在裂缝、孔隙之中。这2种方沸石的存在形式、晶体形态、伴生矿物各不相同,其中纹层型方沸石多与白云石共生,晶体粒径小于0.04,mm,为泥晶结构;充填型方沸石多与黄铁矿、有机质共生,晶体粒径大于0.04,mm,为粉晶结构。根据主、微量元素及碳、氧同位素分析结果,计算出古盐度平均为28.8‰,Sr/Ba值平均为2.93,表明渤海湾盆地北塘凹陷沙河街组三段沉积时期为碱—咸溶液沉积环境,具备形成方沸石的条件。电子探针测试的Si/Al值表明,这2类方沸石母质来源不同,纹层型方沸石母质为黏土矿物,而充填型方沸石母质与热液有关。与国内含方沸石白云岩的盆地进行对比,并从岩石学特征、形成温度等方面进行分析,认为研究区方沸石有2种成因,其中纹层型方沸石是同生成岩阶段的产物,而充填型方沸石则受到热液流体的影响。     

白云鄂博矿床碳酸岩墙/脉和赋矿白云岩中流体包裹体研究

Fluid inclusion study has been carried out for the carbonatite dykes/veins and the ore-hosted dolostone of the Bayan Obo superlarge REE-Fe-Nb deposit in order to provide the evidence and constraint for their origin. Based on the detailed geological observation and mineralogical investigation, the heating and cooling stage and laser Raman spectroscopy were mainly used for the laboratory work of this study. Following results have been obtained： （ 1 ） The discovery of melt and melt-fluid inclusions from carbonatite dykes/veins in the Dulahara and Jianshan Mountains, combined with the fine-grained （aplitic） texture of rocks, as well as the types and features of fluid inclusions such as CO2 enrichment, higher homogenization temperature, provides a direct evidence for the magmatic origin of these dykes/veins. （2） The carbonatite dykes/veins distributed in two regions, nearby the axis of the Kuangou anticline and in the east to Bayan Obo town, mainly show coarse-grained texture. No melt inclusion was found, and the fluid inclusions possess features of less CO2, lower homogenization temperature and higher salinity. They are tentatively identified as veins formed by some carbonate-rich hydrothermal solution. （3） Bedding carbonate layers/lens within the hanging wall and foot wall of ore-hosted dolostone, previously recognized as of magmatic origin, mainly composed by dolomite. The existence of single phase pure aqueous inclusions with very low homogenization temperature indicates their sedimentary origin. （4） The ore-hosted dolostone possesses apparent bedding and laminated structures. No melt inclusion was found, but, both single phase pure aqueous inclusions and CO2 bearing muhi-phase fluid inclusions coexisted in dolostones. In the direction towards ore-bodies, the homogenization temperature and CO2 contents of fluid inclusion show an increasing tendency. It indicates the sedimentary origin of dolostone superimposed by late fluid metasomatism.     

贵州施秉云台山白云岩地球化学特征及成因探讨

贵州省施秉县云台山景区喀斯特地貌主要由寒武纪白云岩组成,其白云石含量多在90%以上,无论是基底中的白云石,还是内碎屑中的白云石均呈自形-半自形晶体。白云岩中CaO的平均含量为30.4%,MgO的平均含量为21.7%,与白云岩的理想含量相当。白云岩Sr的平均含量为72.4×10^-6,Sr/Ba比值大于1,反映其为海相沉积。白云岩的稀土总量低,仅为12.54×10^-6,Eu具较弱负异常,Ce基本无异常,稀土配分模式为轻稀土富集的右倾型。白云岩的形成环境总体表现为局限台地上的泻湖潮下环境,水体较浅,水流不畅,水动力弱-中等。成岩环境以弱还原-还原条件为主,干燥炎热是其古气候条件的特点。在干燥炎热的气候条件下,先期形成的碳酸钙沉积物,经强烈蒸发而形成泻湖卤水,通过向海方向的渗滤回流被交代而形成白云岩,属准同生期-早成岩阶段近地表的交代白云岩。     

新疆三塘湖盆地中二叠统芦草沟组湖相白云岩成因*

新疆三塘湖盆地中二叠统芦草沟组发育湖泊背景下的白云岩、灰岩、黑色泥岩、页岩及碎屑岩的互层沉积。白云岩主要有两类：一类为粉—泥晶白云岩,主要由含量约70％的泥晶白云石和含量约30％的粉晶白云石构成,白云石有序度为0.48,扫描电镜下主要有菱形、他形、球状和管状4种微形态,自形程度较好的菱形晶体多为含铁白云石;另一类为方沸钾长白云岩,主要由晶粒为0.08～0.35mm的细粒方沸石、泥晶钾长石（透长石）、泥晶白云石和铁白云石构成,个别为粗晶白云石,白云石有序度0.58。与粉—泥晶白云岩中的白云石相比,方沸钾长白云岩中的白云石以高的铁、锰含量为特征,扫描电镜下多为半自形的菱形晶体。两类白云岩中白云石的有序度均较低,且均为富Sr白云石,内部均缺乏次生交代证据。通过对两类白云岩成分、微量元素及稳定同位素的差异性分析,认为尽管两类白云岩都形成于浅—半深湖相强还原沉积环境,但是它们的形成机制有所不同,粉—泥晶白云岩具有原生沉淀白云石的特征,其中球状及管状的白云石可能与微生物吸附作用有关,而他形及菱形的白云石为直接沉淀的原生白云石;另一类方沸钾长白云岩中的白云石及铁白云石可能与湖底热泉的喷流沉积作用有关。     

塔东北库鲁克塔格地区中上寒武统白云岩类型与孔隙演化*

对塔东北库鲁克塔格隆起的乌孜里塔格剖面中上寒武统白云岩的岩石学、成岩作用、裂隙—孔隙发育与充填等特征研究认为：可划分为有序度逐渐增加的粉晶白云岩、粉细晶白云岩、中细晶白云岩和中粗晶白云岩及晶洞中的中粗晶、巨晶和鞍形白云石等4种类型;分别对应于早期准同生—浅埋、中浅埋藏、中等埋藏和构造断裂—热液（热卤水）作用4期的成岩阶段;其中,沿走滑断裂—裂隙带、呈不规则的“侵入体” 具有斑点状、条纹—条带、雁行状—斑马、角砾状和不规则状结构的中粗晶、粗晶、巨晶（部分为鞍形）白云岩（石）,一般不发光或呈昏暗的暗红色,具有与加拿大西部盆地典型的热液白云岩相似的特征;中上寒武统白云岩存在4～5期构造裂隙和3期以上的充填作用;热液白云岩中以晶间孔、晶间溶孔（洞）、裂隙及沿裂隙的扩溶孔洞为主,主要有二世代的白云石和方解石和少量沥青、石英、微量硬石膏和重晶石等多期充填作用。与西加盆地寒武系部分或全部交代充填缝洞及角砾构造、受来自落基山造山带的晚白垩世至古近系拉腊米（Laramide）构造的被排驱的热液流体交代形成的典型热液白云岩稍有不同,海西晚期（晚二叠世）及燕山—喜马拉雅期（晚白垩世—第四纪）沿挤压—走滑断裂排驱的地层热卤水循环—扩散与交代作用可能是本区热液白云岩的主要成因,储集空间主要由中、晚期构造断裂—裂隙（溶蚀）所致,但不排除成岩早期埋藏或晚期大气水作用对其影响。     

重庆綦江观音桥剖面观音桥层的岩性新认识*

重庆綦江观音桥剖面是上奥陶统观音桥层(组)的建层(组)剖面。该剖面上奥陶统和下志留统地层连续,在前人研究中被广泛提及。观音桥层是奥陶系顶部层位,含较多特征明显的赫南特贝化石,可能反映了赫南特冰期海平面下降。在前人相关文献中均提及观音桥剖面观音桥层的岩性为灰岩,但本次研究发现,对观音桥层岩石滴稀盐酸时一般起泡较微弱,显微薄片、扫描电镜、阴极发光测试均显示观音桥层白云石含量通常大于50%,呈微晶—粉晶结构,自形晶—半自形晶,方解石含量常小于15%,因此所观察到的观音桥剖面观音桥层的岩性是(灰质)白云岩。进一步分析表明: 在阴极发光下白云石不发光,方解石呈现较强的红色光; 扫描电镜测试显示白云石多为含铁白云石; 显微薄片显示白云岩中少量白云石发生去云化作用,被方解石交代; 碳、氧同位素测试显示白云石碳同位素较腕足类化石及方解石脉偏负,腕足类化石碳、氧同位素与同期海水不一致。上述分析表明观音桥层碳酸盐岩经历了较强的成岩作用影响,推测观音桥层白云石化主要发生于成岩期。这一认识与80多年来关于綦江观音桥剖面观音桥层岩性的认识不一致,对白云岩的识别有助于更深刻认识奥陶纪—志留纪界限地质事件及环境变化。     

Characterization of the Microbial Dolomite of the Upper Sinian Dengying Formation in the Hanyuan Area of Sichuan Province, China

The algal dolostone of the Upper Sinian Dengying Formation (corresponding to the Ediacaran system) in the Upper Yangtze Platform of China possesses a rich diversity of microorganisms and is an ideal site for the study of ancient microbial dolomite. We focused on algal dolostone and its microbial dolomite in the Hanyuan area of Sichuan Province, China. The macroscopic petrological features, microscopic morphology, texture characteristics of the fossil microorganisms and microbial dolomite, and geochemical characteristics were investigated. We found rich fossil microorganisms and microbial dolomites in the laminated, stromatolithic, uniform and clotted (algal) dolostones. The microorganisms present were mainly body fossils of cyanobacteria (including Renalcis, Girvanella, Nanococcus, and Epiphyton) and their trace fossils (including microbial mats (biofilms), algal traces, and spots). In addition, there was evidence of sulfate-reducing bacteria (SRB), moderately halophilic aerobic bacteria, and red algae. The microbial dolomites presented cryptocrystalline textures under polarizing microscope and nanometer-sized granular (including spherulitic and pene-cubical granular) and (sub) micron-sized sheet-like, irregular, spherical and ovoidal morphologies under scanning electron microscope (SEM). The microbial dolomites were formed by microbially induced mineralization in the intertidal zone and lagoon environments during the depositional and syngenetic stages and microbially influenced mineralization in the supratidal zone environment during the penecontemporaneous stage. The microbial metabolic activities and extracellular polymeric substances (EPS) determined the morphology and element composition of microbial dolomite. During the depositional and syngenetic stages, the metabolic activities of cyanobacteria and SRB were active and EPS, biofilms and microbial mats were well-developed. EPS provided a large number of nucleation sites. Accordingly, many nanometer-sized pene-cubical granular and (sub) micron-sized sheet-like microbial dolomites were formed. During the penecontemporaneous stage, SBR, cyanobacteria, and moderately halophilic aerobic bacteria were inactive. Furthermore, nucleation sites reduced significantly and were derived from both the EPS of surviving microorganisms and un-hydrolyzed EPS from dead microorganisms. Consequently the microbial dolomites present nanometer-sized spherulitic and micron-sized irregular, spherical, and ovoidal morphologies. Overall, the microbial dolomites evolved from nanometer-sized granular (including spherulitic and pene-cubical granular) dolomites to (sub) micron-sized sheet-like, irregular, spherical and ovoidal dolomites, and then to macroscopic laminated, stromatolithic, uniform, and clotted dolostones. These findings reveal the correlation between morphological evolution of microbial dolomite and microbial activities showing the complexity and diversity of mineral (dolomite)-microbe interactions, and providing new insight into microbial biomineralization and microbial dolomite in the Precambrian era.