鄂尔多斯盆地环江地区长7储层沉积相研究

环江地区长7储层底部广泛发育张家滩高阻泥岩,为中生界优质烃源岩,源储接触关系明显,砂体含油饱和度高,是勘探开发的重要储层。以岩心观察的岩石相标志及测井相分析为基础,通过地层砂地比、单井相剖面的相序分析,对鄂尔多斯盆地环江地区长7储层沉积相类型及发育规律进行综合研究。结果表明:环江地区长7期主要沉积体系属于河流三角洲相和湖泊相沉积体系,发育三角洲前缘亚相和浊积扇亚相,主要沉积微相类型包括有水下分流河道、水下天然堤、分流间湾、浊积水道、浊积水道前缘、浊积水道间。根据沉积微相展布和演化规律可以得出研究区的沉积模式。     

The lowermost Mississippi River: a mixed bedrock‐alluvial channel

In this study, the distribution of channel‐bed sediment facies in the lowermost Mississippi River is analysed using multibeam data, complemented by sidescan sonar and compressed high‐intensity radar pulse seismic data, as well as grab and core samples of bed material. The channel bed is composed of a discontinuous layer of alluvial sediment and a relict substratum that is exposed on the channel bed and sidewalls. The consolidated substratum is made up of latest Pleistocene and Early Holocene fluvio‐deltaic deposits and is preferentially exposed in the deepest thalweg segments and on channel sidewalls in river bends. The exposed substratum commonly displays a suite of erosional features, including flutes that are quantitatively similar in form to those produced under known laboratory conditions. A total of five bed facies are mapped, three of which include modern alluvial deposits and two facies that are associated with the relict substratum. A radius of curvature analysis applied to the Mississippi River centreline demonstrates that the reach‐scale distribution of channel‐bed facies is related to river planform. From a broader perspective, the distribution of channel‐bed facies is related to channel sinuosity — higher sinuosity promotes greater substratum exposure at the expense of alluvial sediment. For example, the ratio of alluvial cover to substratum is ca 1·5:1 for a 45 km segment of the river that has a sinuosity of 1·76 and this ratio increases to ca 3:1 for a 120 km segment of the river that has a sinuosity of 1·21. The exposed substratum is interpreted as bedrock and, given the relative coverage of alluvial sediment in the channel, the lowermost Mississippi River can be classified as a mixed bedrock‐alluvial channel. The analyses demonstrate that a mixed bedrock‐alluvial channel boundary can be associated with low‐gradient and sand‐bed rivers near their marine outlet.     

Alluvial fan and wetland interactions: evidence of seasonal slope wetlands from the Silurian of south central Wales,UK

Distal environs of the Ludlow‐age Trichrug Formation from south central Wales (UK) detail deposition on the outer fringe of an ephemeral debris flow‐dominated alluvial fan. Debrites and subordinate sheetflood deposits are interbedded with sporadic thin sandstone‐dominated heterolithic units deposited in shallow, ephemeral ponds in the axial valley. The latter slope wetland system fringed the permeable alluvial fan deposits, being maintained by streamflow, precipitation and ground water recharge. A prolonged high water table is indicated by low chroma intervals interpreted as the result of gleying. A variety of redoximorphic indicators, including colour mottling and ferricrete concretions, are evidence of iron mobilization and concentration associated with a seasonally fluctuating water table. The slope wetlands were colonized periodically by Skolithos‐generating organisms, most likely to have been arthropods. The widespread occurrence of redoximorphic indicators and ferricrete contrasts markedly with calcrete Vertisols in penecontemporaneous continental deposits (Lower Old Red Sandstone) of the region. It is likely that the alluvial fan‐toe area was the site of a wetland depression, which maintained a high, though fluctuating, water table. In contrast the alluvial channel reaches of the surrounding drainage network were significantly better drained, with floodplains prone to wetting and drying and Vertisol palaeopedogenesis.     

Tectonic and climatic controls on Holocene channel migration,incision and terrace formation by the Rio Grande in the Palomas half graben,southern Rio Grande rift,USA

In order to evaluate potential effects of tectonics and climate change on the behaviour of the axial Rio Grande in the Rio Grande rift, a 16·5 km stretch of modern floodplain and Holocene terraces were mapped in the tectonically active Palomas half graben, south‐central New Mexico, USA. In addition, 51 cores and natural exposures were logged and 20 radiocarbon dates were obtained from charcoal, bulk organic matter, mollusc shells and pedogenic calcite. The Holocene alluvium comprises four terraces above the modern floodplain, each of which formed by a period of river incision followed by stability and renewed floodplain construction to a level below that of the previous terraces. Estimated times of incision between Terraces I and II, II and III, and III and IV are after 12 400, 8040 to 5310, and 760 to 550 yr bp , respectively, whereas the incision between Terrace IV and the modern floodplain occurred within the last 260 years. Although there is some evidence for tectonic control on river behaviour in the southern part of the basin, terrace formation is interpreted as being related to climate change, with periods of incision corresponding to times of increased aridity and low sediment/water discharge ratio in the Rio Grande. This process may have resulted from a reduction in intensity and magnitude of summer storms which supply sediment to the axial river, coupled with an increase in spring discharge peak caused by snowmelt in upstream mountain catchments.     

Impact of the magnitude and frequency of debris‐flow events on the evolution of an alpine alluvial fan during the last two centuries: responses to natural and anthropogenic controls

The dynamics and the surface evolution of a post‐LGM debris‐flow‐dominated alluvial fan (Tartano alluvial fan), which lies on the floor of an alpine valley (Valtellina, Northern Italy), have been investigated by means of an integrated study comprising geomorphological field work, a sedimentological study, photointerpretation, quantitative geomorphology, analysis of ancient to modern cartography and consultation of historical documents and records. The fan catchment meteoclimatic, geological and geomorphological characteristics result in fast rates of geomorphic reorganization of the fan surface (2 km²). The dynamics of the fan are determined by the alternation of low‐return period catastrophic alluvial events dominated by non‐cohesive debris flows triggered by extreme rainstorms which caused aggradation and steepening of the fan and avulsion of its main channel, with periods of low to moderate streamflow discharge punctuated by low‐ to intermediate‐magnitude flood events, causing slower but steady topographic reworking. The most ancient parts of the fan surface date back at least to the first half of the 19th century, but most of the fan surface has been restructured after 1911, mainly during the debris‐flow‐dominated events of 1911 and 1987. Phases of rapid fan toe incision and fan degradation have been recognized; since the 1930s or 1940s, the Tartano fan has been subjected to a state of deep entrenchment and narrowing of the main trunk channel and distributary area. Post‐Little Ice Age climate change and present‐day surface uplift rates have been considered as possible explanations for the observed geomorphic evolution, but tectonic or climatic controls cannot account for the order of magnitude of the erosional pace. Anthropogenic controls plausibly override the natural ones: in particular, the building of a dam in the late 1920s, about 2 km upstream of the fan, seems to have triggered fan dissection, having altered the sediment discharge through sediment retention. Copyright © 2011 John Wiley & Sons, Ltd.     

惠民凹陷孔店组末端扇沉积及其储层特征

惠民凹陷孔店组为末端扇沉积,中部亚相是其沉积砂体的主体.根据岩芯观察并结合地震资料,将末端扇中部亚相划分为分流河道、河道漫溢和泥滩三种沉积微相.孔店组砂岩类型主要为中细粒的长石砂岩和岩屑长石砂岩.末端扇储层中发生了多种类型的成岩作用,主要的自生矿物包括黏土矿物、碳酸盐、石英和长石等.孔店组砂岩主要受到埋藏成岩作用的影响...     

徐家围子断陷下白垩统营城组四段层序地层与沉积体系发育特征

徐家围子断陷下白垩统营城组四段是裂谷盆地火山喷发背景下发育的粗碎屑岩地层,是天然气储层。利用该区钻井、岩芯、测井和高分辨率三维地震资料,按照层序地层的原理对营四段层序地层进行了分析,以岩相分析为基础确定了营四段沉积体系类型。研究表明徐家围子断陷营四段发育营四下层序（Sq1）和营四上层序（Sq2）两个三级层序。营四下层序...     

东营凹陷盐22块沙四上亚段砂砾岩粒度概率累积曲线特征

在岩芯观察和沉积相分析基础上,利用粒度分析资料对东营凹陷北部陡坡带盐22块沙四上亚段近岸水下扇砂砾岩体的粒度概率累积曲线进行了研究。研究表明,该地区近岸水下扇砂砾岩中的粒度概率累积曲线主要包括：＂上拱弧形＂、＂简单一段式＂、＂准牵引流型＂等3种基本类型和＂近似上拱弧形＂、＂台阶状多段式＂、＂低斜率两段式＂、＂低斜率三段...     

荔湾3-1井区珠江组深水扇高分辨率层序分析及应用

以高分辨率层序分析为指导思想,以岩芯和测井分析为基础,结合地震资料对荔湾3-1井区珠江组下部深水扇沉积层序界面和海泛面成因类型进行综合研究,探讨了深水扇短期旋回结构类型和分布规律,建立了主要产层时间—地层格架,并对地层格架中的小层砂体进行劈分和等时追踪对比,讨论了不同基准面旋回条件下储层发育特征。通过层序—岩相古地理编...     

Mixing of geothermal and non-geothermal fluids in shallow aquifers in the Germencik-Nazilli area,Büyük Menderes Basin (SW Turkey)

This study observes groundwater hydrochemical characteristics during mixing between geothermal and non-geothermal fluids in Germencik–Nazilli area in the Büyük Menderes Basin (SW Turkey). Hydrogeochemical features of 32 non-geothermal, geothermal and surface samples were studied. The mean temperatures of the geothermal reservoirs are calculated to be 150–240 °C in Germencik field, based on Na-K-Mg geothermometry. Hydrochemical characteristics of Germencik geothermal fluid differ from non-geothermal fluids, mainly Na-Cl-HCO₃-type geothermal fluid, while non-geothermal fluid is mostly Ca-Mg-HCO₃-SO₄ type. High contents of some minor elements in geothermal fluids are most likely sourced from prolonged water-rock interaction, reflecting the signals of flow paths and residence times. A mass-balance approach was used to calculate mixing ratios between geothermal and non-geothermal fluids based on B, Cl and Na concentrations. Germencik field is considerably characterised by rising geothermal fluids and overlying non-geothermal fluids. The amount of water stored in the Quaternary aquifer evolved from a deep thermal source is low in Germencik (.5–40% geothermal fluid in non-geothermal wells). Mixing between geothermal and non-geothermal fluids has been caused by groundwater utilisation practices and is increased close to active faults. Irrigation of the shallow groundwater composition is considered as influx of low-temperature geothermal fluid.