板桥-合水地区长63储层成岩相孔隙结构特征及优质储层分布

利用铸体薄片、扫描电镜、常规压汞、恒速压汞及相渗等资料,研究了板桥-合水地区长6₃储层成岩相类型及其微观孔隙结构特征,总结了不同成岩相的测井响应特征,确定了纵向及平面分布规律。结果表明优质成岩相的展布受沉积相、成岩作用与孔隙结构共同控制,尤其是喉道分布才是控制砂岩储层渗透性的主要因素。水云母胶结-残余粒间孔相和水云母胶结-长石溶蚀相储层主要分布于半深湖相重力流复合水道浊流沉积中,细-微细喉道发育,孔喉连通性好,渗流能力最好,油水呈相对均匀的渗流,孔隙内的油气极易通过喉道被开采出来;绿泥石胶结相、水云母胶结弱溶蚀相储层位于分支水道边缘,呈孤岛状分布,孔喉半径小但分布均匀,渗流能力中等-差;碳酸盐胶结相、碳酸盐+水云母胶结相储层主要发育在分支水道间,孔隙结构发育程度差,喉道细小且孔喉连通性差,富集于孔隙中的油气难以通过小喉道,采收率低。     

The deep-lake deposit in the Upper Triassic Yanchang Formation in Ordos Basin, China and its significance for oil-gas accumulation

The deep-lake facies of the Yanchang Formation represents a large outflowing lake basin in the Ordos area. Its deposition can be divided into four stages lake genetic and expanding stage, peak stage, inversion stage and dying stage. All the stages are obviously consistent with the evolution of depositional environment and the paleoclimate in the region. The study indicates that the lake basin has evolution fluctuations from highstand to lowstand for four times in its evolution history, and the deposition center of the lake has not obviously moved, staying along the Huachi-Yijun belt. The deep lake sedimentary system mainly consists of deep water deltas and turbidite fans during the entire evolution course of the lake basin in the Late Triassic. The former mainly developed on the slope of steep shore of the delta in the early period of the deep-water expansion and gradually experienced a big shift from deep-water deltas to shallow-water platform delta. And the latter appeared almost in all the above stages and had two types of turbidite fans, slope-moving turbidite fans and slump turbidite fans. The slope-moving turbidite fans have relatively complete facies belts overlapping one another vertically and consist of the slope channel of inter fans, the turbidite channel, inter turbidite channel and turbidite channel front of middle fans and outer fans (or lakebottom plain). However, the slide-moving turbidity fans are formed in the deep lake with their microfacies difficult to be distinguished, and only the center microfacies and edge microfacies can be determined. The two types of the turbidity fans are similarly distributing in the near-root-slope and far-root-slope regions. The deep-lake deposition governs the distribution of the hydrocarbon and reservoir, while the slope-moving turbidite fans are excellent reservoirs for oil-gas exploration due to their great thickness, widespread distribution and accumulation properties.     

Microbialite of anoxic condition from Permian-Triassic transition in Guizhou,China

Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.     

俯冲型和碰撞型含矿斑岩地球化学组成的差异

Cu-Mo-Au含矿斑岩不仅可以形成于与洋壳俯冲相联系的弧环境,而且也产于碰撞造山带内。通过对比俯冲型和碰撞型含矿斑岩的地球化学特征,发现它们特别在微量元素上具有较大差别,暗示它们有着不同的物源区组成或形成机制。同冈底斯带碰撞型含矿斑岩相比,太平洋东岸俯冲型含矿斑岩有着明显高的HREE和Y含量,低的Sr/Y、(La/Yb)_N以及(Dy/Yb)_N比值,表明其物质源区不含或含有少量的石榴子石并可能以角闪石组成为主。统计发现这些俯冲型含矿斑岩部分样品具有埃达克岩地球化学特征,但大部分样品却显示出具有与正常岛弧系列火山岩相似的特征,它们很可能是板片释放流体交代地幔楔形成的熔体并在后期经历MASH过程的产物。冈底斯带碰撞型含矿斑岩具有典型埃达克岩地球化学特征,指示其形成条件达到了石榴子石相变,可能形成于增厚的下地壳,其物质源区很可能与前期的洋壳俯冲有着密切的联系。普朗-雪鸡坪含矿斑岩具有与俯冲型含矿斑岩十分相似的地球化学特征,它们有可能是西向俯冲的甘孜-理塘洋发生断离,进而诱发前期俯冲流体交代的富集地幔楔发生部分熔融的产物,而并非是俯冲洋壳直接发生部分熔融的产物。     

华南晚古生代末超高温变质作用:以十万大山花岗岩中麻粒岩包体为例

广西东南部大容山-十万大山地区过铝质(S型)花岗岩中包含丰富的副变质麻粒岩包体.部分麻粒岩包体保留了尖晶石+石英、斜方辉石+夕线石±石英等超高温变质矿物组合,指示这些麻粒岩包体曾经历了超高温变质作用.矿物温压估算结果显示:峰期温压条件为7.5～8.0kbar,950～1000℃,峰后退变质温压条件为3.2～3.7kba...     

东北地区晚古生代-中生代I型和A型花岗岩Nd同位素变化趋势及其构造意义

中国东北地区位于中亚造山带巨型增生陆缘的东段,分布着巨量的具有新生特征的显生宙花岗岩和火山岩。本文对东北地区晚古生代-中生代I和A型花岗岩年代学和Nd同位素组成开展了综合分析和研究。东北地区的I型花岗岩有两种Nd同位素变化趋势:一是以额尔古纳和兴安地块为代表,其εNd(t)随着年龄变新而增大,与造山带垮塌、软流圈上涌的幔源熔体或蒙古-鄂霍茨克洋的俯冲交代地幔楔熔体加入引起的地壳增生作用相关。二是以松嫩地块西南区和张广才岭为代表,εNd(t)随着年龄变新而下降,反映花岗岩的熔融源区有从早期的新生岛弧中、下地壳向晚期含更多再循环物质的中、上地壳迁移的趋势。A型花岗岩侵位时代主要有三期,总体上具有正的εNd(t)值,绝大部分tDM21.0Ga,反映了东北地区强烈的地壳增生作用。晚古生代A型花岗岩主要沿着贺根山-黑河断裂分布,可能与兴安和松嫩地块碰撞后伸展作用相关;早中生代A型花岗岩主体分布于张广才岭,与松嫩、佳木斯和兴凯地块的碰撞后伸展作用相关;早白垩世A型花岗岩遍布整个东北地区,可能与古太平洋板块俯冲、后撤导致的区域性伸展作用相关。晚古生代-中生代花岗岩的Nd二阶段模式年龄(tDM2)与侵位年龄(t)的对比展示了东北各构造单元地壳增生作用的差异。与华北北缘中生代花岗岩的特征相似,额尔古纳和佳木斯地块的花岗岩表现出tDM2t+1000Ma的特征,表明这两个地块具有古老的结晶基底。兴安地块、松嫩地块西南区和张广才岭花岗岩的tDM2和侵位年龄差值集中在300~1000Ma,反映不同属性(年轻vs.古老)的地壳物质对熔融源区的贡献。东北地区tDM2和侵位年龄差值小于300Ma的花岗岩岩体极少,仅有乌兰浩特的查干岩体一例,可能由新近增生的新生地壳熔融形成。由Nd同位素特征显示,晚古生代-中生代东北地区显著的地壳增生作用主要发生在缝合带和岩石圈规模的断裂带,幔源岩浆沿断裂带上升到地壳不同深度并形成高εNd(t)和低tDM2的中酸性火成岩。除几个特殊岩体表现出过于亏损或富集Nd同位素的特征,早白垩世东北地区酸性火成岩的Nd同位素组成相近,εNd(t)值集中在0~+3之间,可能暗示此时期东北地区的中、下地壳成分组成趋于一致并与同时期的古太平洋俯冲作用有关。我们的结果显示东北地区晚古生代-中生代花岗岩的起源与古亚洲洋、蒙古鄂霍茨克洋和古太平洋的构造演化相关。这三个古大洋的扩张和俯冲作用提供了大量新生地壳物质,而新生和再循环地壳物质的重熔形成了东北地区大规模的显生宙花岗岩及其对应成分的喷出岩。     

Community replacement sequences and paleoenvironmental changes in reef areas of South China from Late Permian to Early Triassic exemplified by Panlongdong section in northeastern Sichuan Basin

The well-known Permian Changhsingian calcisponge reef located at Panlongdong section,Xuanhan county,northeastern Sichuan Basin has attracted wide attention.Due to severe dolomitization and poor quality of the fossils,the P-T boundary in this section is difficult to determine.This study,for the first time,recognized six communities in the Upper Permian Changhsingian Changxing Formation through the Lower Triassic Induan Feixianguan Formation of the Panlongdong section.They are Bryozoan-Archaeolithoporella-calcisponge Community,Calcareous green algae-foraminifer-crinoid Community,Microgastropod-foraminifer Community,Ostracod-microgastropod-cystic microbe Community,Ostracod-small brachiopod Community,and Non-calcified cyanobacteria Community.By using community replacement and palaeoenvironmental analysis,for the first time,we set the P-T boundary of the Panlongdong section at the middle of the calcimicrobialite containing cystic microbes.The community replacement sequence in the Panlongdong section is similar to that in other contemporaneous sections in reef areas of South China,indicating universal palaeoenvironmental changes during the Permian-Triassic transition.The results show that:(1)Changhsingian calcisponge reefs in South China generally vanished before the mass extinction and may be related to the large regression in the Late Permian.(2)The Calcareous green algae-foraminifer-crinoid Community replaced reef community and continued till the mass extinction.The mass extinction was probably related to the global sea-level drop.(3)The first aftermath community was dominated by specialized microgastropods,followed by the microbes,and then by the specialized microgastropods and small brachiopods.The succession of the three communities reflected the change in environmental conditions from dysoxic to anoxic and again to dysoxic.(4)In the Early Triassic,the relict community in shallow sea had very low diversity and low abundance,and was dominated by crinoids,gastropods,and bivalves.     

重庆二叠系-三叠系界线地层微生物岩新认识

通过对重庆老龙洞二叠系-三叠系界线附近的微生物岩的研究,认为微生物岩的树枝状构造的形成有两种控制因素:(1)成岩作用,成岩流体对碳酸盐沉积物颗粒之间的孔隙及化石内部的孔隙的胶结作用,以及碳酸盐沉积物组分的重结晶作用,使受成岩作用影响的区域因晶体较粗在露头上表现为深颜色的树枝状和斑点状构造;(2)微生物的影响。在微生物富集的地方,微生物死亡腐烂后形成孔隙,成岩流体易于在这些区域运移,在孔隙中形成胶结物,使这些区域成为露头上颜色较深的树枝状和斑点状构造。岩石中的微生物化石形态不规则,在薄片上呈蝴蝶状、云朵状、不规则圆形的或者新月形等形状,大小在100～600μm之间,内部被方解石胶结物充填,没有保存任何内部构造。根据形态和大小,推测这种化石可能是某种细菌的菌落形成的。     

The deep-lake deposit in the Upper Triassic Yanchang Formation in Ordos Basin,China and its significance for oil-gas accumulation

The deep-lake facies of the Yanchang Formation represents a large outflowing lake basin in the Ordos area. Its deposition can be divided into four stages: lake genetic and expanding stage, peak stage, inversion stage and dying stage. All the stages are obviously consistent with the evolution of depositional environment and the paleoclimate in the region. The study indicates that the lake basin has evolution fluctuations from highstand to lowstand for four times in its evolution history, and the deposition center of the lake has not obviously moved, staying along the Huachi-Yijun belt. The deep lake sedimentary system mainly consists of deep water deltas and turbidite fans during the entire evolution course of the lake basin in the Late Triassic. The former mainly developed on the slope of steep shore of the delta in the early period of the deep-water expansion and gradually experienced a big shift from deep-water deltas to shallow-water platform delta. And the latter appeared almost in all the above stages and had two types of turbidite fans, slope-moving turbidite fans and slump turbidite fans. The slope-moving turbidite fans have relatively complete facies belts overlapping one another vertically and consist of the slope channel of inter fans, the turbidite channel, inter turbidite channel and turbidite channel front of middle fans and outer fans (or lakebottom plain). However, the slide-moving turbidity fans are formed in the deep lake with their microfacies difficult to be distinguished, and only the center microfacies and edge microfacies can be determined. The two types of the turbidity fans are similarly distributing in the near-root-slope and far-root-slope regions. The deep-lake deposition governs the distribution of the hydrocarbon and reservoir, while the slope-moving turbidite fans are excellent reservoirs for oil-gas exploration due to their great thickness, widespread distribution and accumulation properties.