皖南地区荷塘组页岩气成藏条件及有利区预测

通过野外实地观察、样品采集及系列实验分析发现,皖南下扬子区下寒武统荷塘组页岩在研究区内分布广泛,沉积厚度大(约60~360 m),有机质丰度高(达0.5%~7.2%),热演化程度较高(Ro为2.0%~5.5%),达高-过成熟阶段晚期,具有较好的生烃潜力;储集层孔隙度平均为0.716%,为游离气提供了一定的储存空间,等温吸附实验测得吸附气含量平均为0.443 cm3/g,表明研究区页岩具有较强的吸附能力。通过综合研究认为,石台—黟县—泾县—宁国一带为今后的有利勘探区,分布面积约9 100 km2.     

Long‐term fish assemblages of inner bends in a large river

We sampled fishes at 17 inner bend sites on the Wabash River in 2008 to compare with collections from 1977 to 1997. We used the same seine collection methods as previous years and collected a total of 37 species. Mean site Shannon‐Wiener diversity, species richness, evenness and abundance for all years were similar. We used multivariate analyses to test for patterns in fish assemblage structure among all sites and all years. The multivariate analyses resulted in distinct assemblages for each collection‐year, suggesting shifts in assemblage composition among years. We used separate multivariate analyses to examine fish assemblage variation within individual years. Variation that corresponded to an upstream–downstream pattern was present in 1977 and 2008, but not in 1997. A hydrologic analysis based on daily discharge revealed that eight large flood events occurred from 1928 to 2007, with four of these events during the recent 20 years. We quantified substrate variation at the 17 sites in 2008 and identified a longitudinal gradient in dominant substrate categories with gravel upstream and sand downstream that was correlated with the first axis of the 2008 fish assemblage ordination. We suggest that observed changes in fish assemblages in decadal periods were from hydrologic impacts of large floods on local habitats. Copyright © 2010 John Wiley & Sons, Ltd.     

Using habitat guilds to develop habitat suitability criteria for a warmwater stream fish assemblage

The diversity of fish species found in warmwater stream systems provides a perplexing challenge when selecting species for assessment of instream flow needs from physical habitat analyses. In this paper we examined the feasibility of developing habitat suitability criteria (HSC) for the entire fish community of a warmwater stream using habitat guilds. Each species was placed a priori into a guild structure and habitat data were collected for depth, velocity, Froude number, distance to cover, embeddedness and dominant and subdominant substrate. Correct guild classification was tested with linear discriminant analysis for each species. Correct classification based on habitat‐use data was highest for riffle and pool‐cover guilds, whereas the fast‐generalist and pool‐run classes, the broader niche guilds, were more frequently misclassified. Variables most important for discriminating guilds were Froude number, velocity and depth in that order. Nonparametric tolerance limits were used to develop guild suitability criteria for continuous variables and the Strauss linear index was used for categorical variables. We recommend the use of a wide array of variables to establish more accurate habitat analysis. Additionally, guild HSC can be developed with similar effort to that needed to develop HSC for a small number of individual species. Results indicate that a habitat guild structure can be successfully transferred to another river basin and that habitats for a diverse fish assemblage can be adequately described by a small number of habitat guilds. This approach represents an alternative for incorporating entire fish assemblages into habitat analyses of warmwater stream systems. Copyright © 2010 John Wiley & Sons, Ltd.     

鄂尔多斯盆地奥陶系中组合白云岩储层及圈闭成藏特征

鄂尔多斯盆地下古生界天然气勘探长期以来以奥陶系顶部的古风化壳地层圈闭气藏为目标,近期通过对白云岩成藏机制的深化研究,在古隆起东侧发现了奥陶系中组合新型岩性气藏,其储层主要发育于马家沟组五段5亚段（简称马五₅）白云岩中,储层特征明显不同于奥陶系顶部的风化壳储层。受沉积环境控制,中组合马五₅白云岩呈SN向带状展布,其中靖边西白云岩带由于临近古隆起,水动力条件强,滩相沉积发育,后期经白云石化后形成的白云岩具有“分布面积广、厚度大、岩性纯,南北向连片展布”的特点,且晶间孔发育,为有利的储层。加里东末期,由于盆地整体抬升造成古隆起东侧中组合地层遭受剥蚀,从而与上古生界煤系烃源岩接触,构成良好的源-储配置关系。受岩性相变控制,中组合马五₅滩相白云岩在空间上形成岩性圈闭,有利于油气聚集成藏。     

鄂尔多斯盆地靖西地区奥陶系中组合天然气成因与成藏主控因素

鄂尔多斯盆地靖边气田扩边勘探过程中,在靖西地区下古生界奥陶系中组合白云岩储层中发现了多个含气区,但各含气区及各含气层段天然气的富集程度差异明显,目前尚不清楚造成上述差异的原因。为此,依据天然气组分、碳同位素值等地球化学资料,对比分析了该区奥陶系中组合天然气的成因·与来源,并研究了天然气成藏的主控因素。结果表明:①该区奥陶系中组合天然气与奥陶系上组合、上古生界天然气的成因与来源相似,均以上古生界生成的煤型气为主,但混有一定量的油型气;②受煤系烃源岩生烃中心和源储接触关系的影响,平面上由北向南、纵向上从下奥陶统马家沟组马五_(10)亚段到马五_5亚段,煤型气所占比例依次增大。结论认为,靖西地区奥陶系中组合天然气成藏主要受控于以下因素:①供烃窗口处天然气的充注能力决定了天然气的富集程度;②马五_5—马五_(10)亚段输导通道的差异控制了天然气的纵向运移及分布:③构造与储层叠合关系控制了天然气的横向运移方向及成藏范围。     

大庆长垣中部扶杨油层断裂对储层的控制作用

通过对大庆长垣中部杏树岗、高台子和太平屯构造扶杨油层的断裂和砂体展布特征分析认为,扶杨油层的断裂与砂体具有相互作用关系,即同沉积断裂对砂体的展布具有控制作用,而河道沉积的砂体对断裂形成具有制约作用。断裂与砂体的相互作用对扶杨油层油气运移和成藏具有重要意义,同沉积断裂控制的砂体以垂向向下排烃为主,形成低部位成藏模式,河道砂体与其诱导的断裂共同构成了垂向向上和侧向运移的通道,形成高部位成藏模式。     

浊积砂体油气成藏主控因素的定量研究

东营断陷盆地沉积中心广泛发育了浊积砂体,它与烃源岩间存在密切的成生关系,有利于形成岩性油气藏,但对其含油气性难以定量预测.对该地区大量已钻探浊积砂体油气藏特征进行了剖析.在此基础上,结合测试和模拟试验资料分析,对浊积砂体油气成藏的主控因素进行了研究,并给出了定量评价和预测浊积砂体含油气性的相关界限参数.结果表明,浊积砂体围岩的排烃强度是决定砂体成藏的关键因素.在油源充足的情况下,其含油性则主要受砂体的储集属性和成藏动力及阻力条件的影响.其中,围岩排烃强度大于20×10⁴t/km²、且成藏动力指数大于15%时,易于形成高充满度的油气藏;而厚度小于2m、孔隙度小于12%的砂体则不利于成藏.     

南堡凹陷源上成藏组合油气勘探潜力

南堡凹陷源上成藏组合包括E3d1及Ng、Nm,是目前冀东油田公司增储上产的主力层组.通过构造解析、油气藏解剖、成藏期次确定、成藏过程模拟,揭示源上成藏组合油气成藏机制,分析勘探潜力.指出油气成藏具有两期充注,印Nm沉积早期和晚期;油源断层是源上成藏组合油气成藏的关键要素,在强大源-储剩余压力差作用下,油气沿断层向上运移,为油气成藏提供充足油源.源上成藏组合油气富集受控于油源断层及其相关的构造圈闭.在压扭应力作用下,共轭剪切带形成有利的区带,勘探潜力巨大,是油气勘探的重点.图7表2参15     

陆相断陷盆地层序地层与成藏单元类比分析——以济阳坳陷为例

陆相断陷盆地不同级别的层序地层是不同层次构造运动形式的物质体现，也以不同的方式对应着不同类型的石油地质要素。盆地不同级别成藏单元成因划分的基础是不同层次的成藏要素类型及其作用，通过不同级别层序地层、地质要素及其作用内在联系的分析，认为不同级别的层序地层单元与成藏单元之间可以建立起成因类比关系，一级层序、二级层序、三级层序分别以不同的方式对应于含油气盆地、含油气系统或复式油气聚集带、成藏组合体．从而更加深入地反映陆相断陷位地等时成因地层格架与成藏单元结构间的内在成因联系。     

松辽盆地南部扶余油层低渗透油藏形成机制

从沉积储层特点、烃源岩超压、油气运移动力、油水分布特征等方面深入剖析了松辽盆地南部扶余油层的成藏机制, 据此建立了扶余油层低渗透储层垂向输导、超压控藏大型岩性油气藏成藏模式。预测坳陷区扶余油层低渗透油藏的勘探潜力巨大, 指导勘探取得明显效果。