Facies and seismic analysis of the Late Carboniferous–Early Permian Finnmark carbonate platform (southern Norwegian Barents Sea): An assessment of the carbonate factories and depositional geometries

The late Palaeozoic buried Finnmark platform, in the Norwegian Barents Sea, is a depositional system which developed under major modifications of palaeoclimatic and palaeoceanographic conditions, given by the northward drifting of the Arctic depositional domain beyond the tropical belt, the activity of the Gondwanan icecaps, and the gradual closure of the Eastern European seaway. In this study, detailed core/microfacies analysis from the explorations wells 7128/4-1 and 7128/6-1, combined with new 2D seismic sections and available dataset from previous studies in the eastern Finnmark area, have allowed a re-evaluation of the depositional scenarios associated with the Ørn and Isbjørn/Polarrev Formations. The late Asselian–early Sakmarian depositional record of the Ørn Formation, followed by the middle Sakmarian transition to the Isbjørn/Polarrev Formations, shows depth-related variations in sedimentation modes and a change of the platform morphology.In particular, a shift from Chloroforam to Bryonoderm sedimentation mode took place through a stratified water column during the deposition of the Ørn Formation, over what we suggest was a distally steepened ramp. In the late Sakmarian, the deposition of the Isbjørn/Polarrev Formations, characterised by a full Bryonoderm sedimentation mode, took place through a cooler non stratified water column, leading to the gradual instauration of a homoclinal ramp profile.Among the other results, our integrated study suggests the development of subtidal heterozoan mounds associated with the Ørn Formation, predating the formation of the larger, stacked and well-known heterozoan distal complexes of the Polarrev Formation. Given the good potential of the Ørn Formation within the Finnmark depositional domain, our results may help to improve the assessment of future evaluations of reservoir properties in the area, which are closely associated with the depositional style and their post-depositional modifications.     

陕西定边张韩区块延长组长2储层流动单元研究

利用孔隙度和渗透率参数,将陕西定边张韩区块油藏储层分为4类流动单元.分析各流动单元的物性特征,阐明不同级别流动单元分布特点及其与沉积微相的关系,获得各类流动单元物性特征参数.     

柴达木盆地西北缘现代冲积扇沉积特征及石油地质意义

柴达木盆地处于古亚洲构造域和特提斯－喜马拉雅构造域的结合部，构造应力大而复杂，导致盆内地势起伏大，加上西南暖湿气流受喜马拉雅山系阻隔难以进入境内，盆内气候干旱，最终导致盆地内冲积扇极为发育。通过对大柴旦地区大头羊煤矿、鱼卡河、波门河和八里沟四个冲积扇的实地考察，共观测到3个亚相8个微相：扇根亚相沉积物最粗，分为古沟道、主水道和主水道间微相；扇中亚相沉积物偏细，成熟度增高，分为辫状水道、辫状水道间和纵坝微相；扇缘亚相沉积物最细，流体能量最低，分为水道径流和片流微相。不同沉积微相其沉积特征差异较大，认为古沟道、主水道和辫状水道微相具有较好的储集性能。勘探表明，冲积扇沉积与储层有着密切的关系，其内形成的油藏具有“自我保护”的能力；另外，冲积扇的形成很可能导致上覆地层形成扇背斜油藏，也可能导致下伏基岩形成基岩风化壳油藏。     

沉积学研究中的地层倾角测井资料解释

地层倾角测井资料中包含着丰富的地质信息,它不仅可以反映地层的岩性界面,而且对于地层的时间当量层理面也有所响应,即当地层的沉积构造发生变化时,与之相应的地层倾角和侧向也将随之发生变化。在地展倾角矢量图上,根据倾角矢量随深度的变化关系可以将其划分为五种颜色模式：蓝模式、红模式、绿模式、黄模式和白模式,这五种颜色模式分别反映不同的沉积构造。砂岩体在倾角矢量图上主要表现为三种矢量图模式：ａ.古水流模式—水流层理、顺流加积和进积;ｂ.底线模式—侧向加积和冲蚀接触;ｃ.地层形状模式—压实模式、古水流模式和底线模式可以指示以水流为其搬运介质的沉积砂体,如河道沉积和三角洲沉积,压实模式可以指示岩礁或砂坝。综合分析地层倾角矢量图、地层倾斜方位频率图和画有横向对比线的地层倾角极板曲线图可以研究如下所述的地层沉积学问题：１）地层的形状特征,如地层的厚度、地层的延伸方向和延伸范围、地层面形状。２）地层界面特征,即相邻地层的接触关系,是渐变接触还是突变接触。３）层理特征,如块状层理、纹层状层理和非均质层理。４）沉积旋回和韵律。５）古水流方向和砂体加厚方向。６）砂体微相,即当大的沉积环境（如三角洲沉积环境）已知的条件下,可以识别（如分流河道砂体、河口坝砂体等)砂体微相。     

微相分析在高分辨率层序分析中的运用

以科学合理采出的岩心或露头样品中所获得的微相标志,可提供古水深的线索。微相标志可以有效识别作为建立碳酸盐岩三级层序地层格架基础的陆上暴露面、淹没不整合面、初次海泛面以及最大海泛面等层序界面,还可以识别和解释多种类型的准层序。     

Slope sediments of a Paleocene ramp-to-basin transition in NE Egypt

Received: 9 November 1998 / Accepted: 6 October 1999     

湖南慈利江垭剖面二叠系-三叠系界线层序的沉积微相类型、沉积环境和海平面变化

本文对湖南慈利江垭剖面二叠系-三叠系界线层序(大隆组顶部9.4m和大冶组底部7.5m)进行了详细的沉积微相分析,划分出八种微相类型,并结合露头和光面上的沉积特征,对每种微相的成因和沉积环境进行了分析和讨论。在此基础上,研究了界线附近的沉积环境和相对海平面变化。大隆组顶部层序沉积于相对海平面持续上升阶段,随着相对海平面的上升,沉积环境逐渐由盆地边缘向盆地内部迁移。在大隆组最顶部,相对海平面有一快速的大幅度下降,沉积环境由深水盆地突然转变为浅水台地。之后自大冶组底部向上,相对海平面又逐渐上升,沉积盆地依次经历了滞流盆地、半循环盆地和循环盆地的转换;在距离大冶组底部约7m处,相对海平面开始下降,气候变得极为干燥,沉积盆地转变为蒸发盆地。值得指出的是,大隆组-大冶组界线处的快速海退面正好对应于二叠纪末生物灭绝面,从而表明大海退很可能是造成二叠纪末生物大灭绝的重要原因。     

The rock-avalanche of February 1995 at Claix (French Alps)

The sedimentology of a rock-avalanche involving ca. 7·10³ m³, that happened on February 1995 at Claix, the French Alps, is analysed here. The talus shows a proximal depression due to the impact of the debris, then a grooved area with few, mainly sandy silt deposits and a downslope accumulation of coarse debris that reaches up to 3 m in thickness. The material underwent mass movement as demonstrated by the steep distal front, the strong fabric strength and the thrust planes. The greatest part of the deposits consists of a clast-supported to partially openwork debris with angular clasts over a sheared matrix-supported basal layer. The largest blocks, often more than 1 m in length, are concentrated at the surface and the front. The overall sedimentological characteristics are similar to those of the small dry grain flows that occur usually on rockfall talus, except for the abundance of fine-grained particles that results from intense cataclasis during flow. It is suggested that the deposits of such medium-scale rock-avalanches, probably not uncommon in seismic regions, may have been confused in previous studies with other slope mechanisms such as debris flow and rockfall.     

克拉通盆地不同级次构造—岩相古地理编图思路与实践：以鄂尔多斯盆地早古生代为例

构造—沉积分异思想在地球内部构造地质作用与地球表面沉积响应间建立起了有机联系,可划分为不同序次系统,体现了地球系统思维。以该思想为指导编制了鄂尔多斯盆地早古生代构造—岩相古地理图。盆—山系统级次编图主要体现了不同构造—沉积分异作用对古地理面貌的控制,揭示了古地理演化的动力学机制,反映了不同时期地球深部活动在地表系统的响应;隆—坳系统级次编图揭示出海平面波动过程中不同构造单元沉积环境及充填沉积物的差异;凸—凹系统级次编图清晰展现出东部坳陷内古地貌差异引起的沉积环境分异及生、储、盖物质的分布规律与组合关系。不同级次的构造—岩相古地理图更好地解释了古地理面貌“所以然”的原因,更清晰地揭示了油气成藏物质空间分布规律及其控制因素,从而能更有效指导油气勘探实践。

     

Paleoecology and paleoenvironment of the Middle–Upper Jurassic sedimentary succession,central Saudi Arabia

Four Middle–Upper Jurassic sections from central Saudi Arabia have been investigated to evaluate microfacies types and macro-invertebrate paleocommunities and to interpret their paleoecology and paleoenvironments. The studied Jurassic successions are part of the Middle–Upper Callovian Tuwaiq Mountain Limestone and the Middle–Upper Oxfordian Hanifa Formation. Three main facies were recorded, including mud-supported microfacies, grain-supported microfacies and boundstones. A data matrix comprising 48 macrobenthic species in 35 samples collected from four sections were grouped into fifteen assemblages and one poorly fossiliferous interval by means of a Q-mode cluster analysis. The recorded macrofaunal assemblages have been subdivided into low-stress and high-stress on the basis of hydrodynamic conditions, substrate type, nutrient supply and hypoxia. The low-stress assemblages occur in (a) high-energy paleoenvironments with firm substrates; (b) high-energy shoals with unstable substrates of low cohesion and in (c) low-energy open marine environments with soft-substrates. The moderate- to high-stress assemblages occur in (a) oligotrophic environments with reduced terrigenous input in shelf lagoonal or in restricted inner ramp settings; (b) low-energy, soft substrate environments with hypoxia below the sediment–water interface; and, in (c) high-energy shoals and shelf lagoonal environments. The temporal distribution patterns of epifaunal and infaunal bivalve taxa are controlled by variations in water energy, substrate characteristics and productivity level. The reported litho- and biofacies confirmed that the Callovian Tuwaiq Mountain Limestone and the Oxfordian Hanifa Formation were deposited across wide spectrum of depositional environments, ranging from restricted lagoon to moderately deeper open marine basin, and providing the perfect conditions for macrofossils.