OpendTect系统在层序地层研究中的应用

在等时层序格架建立的基础上,利用地震资料研究各体系域内部沉积体的空间展布、叠置样式和沉积演化过程,进而预测各体系域中砂体的分布,是层序地层学应用于勘探实践的重要内容.OpendTect系统在三维地震倾角扫描的基础上,①以地震采样点空间信息为导向,实现了层序界面控制下的地震小层自动追踪,可以精细刻画出体系域内部沉积体地震反射结构和空间展布;②通过对各层序单元内部地震小层追踪结果进行层拉平,实现了时间域到Wheeler域的自动变换,可以更加直观地分析地层沉积演化历史;③通过沿沉积体内部小层面提取地震属性,实现了等时地层切片的提取,减少了地震属性多解性,提高了预测精度.OpendTect系统提供了一种新的基于层序地层的地震综合解释技术和思路.     

南黄海Heuksan盆地的地震地层学研究

南黄海中的南HEUKSAN盆地是一个介于矩形到菱形之间、大小大致为32 km×13 km的盆地.这个盆地有两个最厚的沉积中心;一个在盆地西部中央,地震双程到时2.2 s的部位;另一个在盆地东部中央位置.二者之间以中央隆起相隔.盆地的地震剖面可以进一步划分为古生代到三叠纪时期的前地堑相沉积,新生代的地堑充填沉积及中新世到上新世时期的的内凹沉积.地堑充填时期的沉积可以分为两个地震层序A和B.层序A和B又可以进一步划分为3到4个亚层序.在南HEUKSAN盆地利用地震层序学的方法对上始新统地震剖面进行了较为详细的分析.认为古水流大部分是从盆地的西部流入的.因此推断其沉积物源主要来自西北部地区,其次来自于盆地的北部.顶积层为三角洲相.根据反射地震剖面的连续性、振幅和反射频率等在上始新统的地震剖面上划分出4个地震相带.地震相A区主要位于两大沉积中心部位.为三角洲前缘泥砂.相带B位于沉积区的西北边缘为平坦三角洲的沙砾.相带C2沿着南部的盆地边缘断裂带分布,为冲积扇.结论认为:始新统的地震解释剖面表明当时主要为三角洲沉积.主要沉积物来自西北的陆源区和南HEUKSAN盆地的西北部.在盆地的南部边缘,沿着盆地的边界断层发育有冲积扇的沉积环境.     

Bed diversity in the shallow water environment of Pappas lagoon in Greece

<正>Acoustic classification systems and the Sediment Trend Analysis method were used to identify and map the bed diversity in a very shallow(3.0m),coastal lagoon,Pappas lagoon,Western Greece. Analogue acoustic data,collected by means of a 100 kHz side scan sonar system,were digitized and classified into six acoustic classes using recently developed acoustic classification systems (SonarClass,TargAn).By comparing the acoustic classes to ground truth data consisting of sediment grain size and visual inspection of the lagoon-bed,it is demonstrated that the six acoustic classes correlate well with the predominant surface sediment types and vegetation.Thus the spatial distribution of the classes can be considered to represent the spatial pattern of the sedimentary assemblages of the lagoon.The grain size trend analysis identified three dominant sediment pathways and directional trends which could be related to the predominant wind direction,the sediment influx through the inlets and the sediment supply from a small stream in the southern part of the lagoon.The integration of acoustic and sedimentological data together with advanced data processing systems leads to a better understanding of the sedimentary,morphological and biological processes in a shallow lagoon in different spatial and temporal scales and will therefore be beneficial to both sedimentological and biotic-diversity studies.     

Establishing the sediment stratigraphy of reservoirs in the southern Pennines,UK

Abstract

Reservoirs in the southern Pennines have been investigated to determine their potential for reconstructing a history of atmospheric pollution. A selection procedure has been used to identify sites with the best chance of obtaining a usable sedimentary record prior to sample collection. Five reservoirs were selected for core collection and sediment analysis using magnetic susceptibility (χlf), particle size, spheroidal carbonaceous particle (SCP) analysis and radiometric dating. Analysis reveals that largely undisturbed sedimentary records exist in the deepest zones of these reservoirs, thus reservoir sediments represent a valuable resource for investigating pollution histories in the southern Pennines.     

大庆台网震级测定偏差研究

对大庆台网深井摆和ＤＫ－１仪器测定的震级偏差进行了研究。发现井下摆测定震级偏低，原因主要是井下摆记录穿透波缺少地面反射产生的二倍效应。ＤＫ－１测定震级偏高，产生偏差原因有两点：冲积层谐振引起地动位移放大；地层结构变化导致位移放大     

Occurrence conditions of hyperpycnal flows, and their significance for organic-matter sedimentation in a Holocene estuary, Niigata Plain, Central Japan

River floods influence sedimentary environments and ecosystems from the terrestrial to the deep-marine. This study documents the occurrence conditions of hyperpycnal flows generated by river floods and related organic-matter sedimentation for Holocene sediments of the Niigata Plain, Central Japan, based on detailed sedimentary facies, total sulfur and total organic carbon content, diatom assemblages and organic-matter composition. Holocene sediments of the Niigata Plain consist of sand, mud and gravel that were deposited in estuarine and fluvial systems during a sea-level rise (15 000–6800 years BP) and stillstand (after 6800 years BP) following the Last Glacial Maximum. Hyperpycnites are present in the upper part of the estuarine lagoon sediments. The depositional age is considered to be about 5000 years BP. The hyperpycnites comprise two successions of a top fining-up unit and a basal coarsening-up unit, and include abundant terrigenous organic matter and freshwater diatoms. A large volume of freshwater is inferred to have flowed into the lagoon during deposition of the upper part of the lagoon sediments. In consequence, hyperpycnal flows may have readily formed in the lagoon, because the halocline was weak. The hyperpycnal flows also produced a layer of concentrated terrigenous organic matter in the uppermost part of the hyperpycnites. The abundant organic matter on the estuarine floor is inferred to have produced anoxic bottom conditions owing to oxidative decomposition by benthic bacteria.     

3D S-wave velocity structure of the Ningdu basin in Jiangxi province inferred from ambient noise tomography with dense array

The Ningdu basin, located in southern Jiangxi province of southwest China, is one of the Mesozoic basin groups which has exploration prospects for geothermal energy. A study on the detailed velocity structure of the Ningdu basin can provide important information for geothermal resource exploration. In this study, we deployed a dense seismic array in the Ningdu basin to investigate the 3D velocity structure and discuss implications for geothermal exploration and geological evolution. Based on the dense seismic array including 35 short-period (5 s-100 ?Hz) seismometers with an average interstation distance of ～5 ?km, Rayleigh surface wave dispersion curves were extracted from the continuous ambient noise data for surface wave tomographic inversion. Group velocity tomography was conducted and the 3D S-wave velocity structure was inverted by the neighborhood algorithm. The results revealed obvious low-velocity anomalies in the center of the basin, consistent with the low-velocity Cretaceous sedimentary rocks. The basement and basin-controlling fault can also be depicted by the S-wave velocity anomalies. The obvious seismic interface is about 2 ?km depth in the basin center and decreases to 700 ?m depth near the basin boundary, suggesting spatial thickness variations of the Cretaceous sediment. The fault features of the S-wave velocity profile coincide with the geological cognition of the western boundary basin-controlling fault, which may provide possible upwelling channels for geothermal fluid. This study suggests that seismic tomography with a dense array is an effective method and can play an important role in the detailed investigations of sedimentary basins.     

Progressive changes in lithological association of the Sanbagawa metamorphic complex,Southwest Japan: Relict clinopyroxene and detrital zircon perspectives

The main tectono‐stratigraphic unit (Shirataki unit) of the Sanbagawa metamorphic complex in central Shikoku is characterized by abundant mafic schist layers that show the mid‐ocean ridge basalt (MORB) affinity. These MORB‐derived schist layers are absent in a southern (structurally lower) domain within the unit. Instead, sporadic occurrences of small metabasite lenses that contain relict igneous minerals (Ti‐rich augite and kaersutite) indicative of alkali basalt magmatism are newly recognized in the southern domain. Compositions of relict clinopyroxene in metabasalt are useful to identify the tectonic setting and origin of the protolith basalt, and those in each unit of the Sanbagawa metamorphic complex are presented. The metamorphic grade of the Shirataki unit generally increases structurally upwards in the southern side of the highest‐grade zone, and metamorphic zonation is subparallel to lithostratigraphic succession. The protolith assemblage of the Shirataki unit shows a distinct change from the southern low‐grade domain (lower Shirataki subunit) composed of terrigenous sedimentary rocks (mudstone and sandstone) with minor alkali basalt to the northern higher‐grade domain (upper Shirataki subunit) consisting of terrigenous and pelagic sedimentary rocks with abundant MORB. The youngest detrital zircon U–Pb ages (ca 95–90 Ma) suggest that both domains have Late Cretaceous depositional ages at the trench. Progressive peeling of oceanic plate stratigraphy during subduction can account for the observed change of lithological association in the Shirataki unit.     

Onshore and offshore seismic and lithostratigraphic analysis of a deeply incised Quaternary buried valley system in the Northern Netherlands

High-resolution seismic data (onshore and offshore), geophysical borehole data as well as detailed lithofacies from airlift boreholes were acquired in northern Netherlands on and around the island of Ameland. Marine and land seismic data combined with information from land boreholes have been explored with the objective of providing a sedimentary model. Qualitative seismic facies analysis of the valley fill commonly shows a thin unit with high amplitude reflectors at the base. Thick units of variable seismic facies (transparent to high amplitude) occur higher up in the sequence. Onlap is common at mid–upper levels within the sandy valley fill (with clay in mm layering), and a transparent seismic facies, corresponding to firm clays, is common at the top. Almost all lithological unit boundaries recognised within core parameters correspond with seismic unconformities within error margins. Subunits contain multiple cyclical trends in gamma ray and grain size. Cyclical trends show lower order fluctuations in gamma radiation on a scale of less than 1 m. Gamma-ray pattern variability between units, e.g. in general coarsening-up or fining-up units, suggests migration of subaqueous outwash fans or ice margin fluctuations. Seismic results could support a headward excavation and backfilling process suggested by Praeg [Morphology, stratigraphy and genesis of buried Elsterian tunnel valleys in the southern North Sea basin [PhD thesis]: University of Edinburgh, 207 pp.; Journal of Applied Geophysics, (this volume)] as being responsible for the formation of buried valleys. On a lithological scale, a more complicated, detailed and cyclical pattern arises. Catastrophic processes are considered unlikely as being responsible for the infill sequence because of the observed small-scale facies variability and because of the presence of diamicton layers. Diamicton layers at the base of basal unconformities as well as higher in sequence could suggest subglacial deformation by grounded ice before and during the valley-fill process.     

A detailed receiver function image of the sedimentary structure in the Bohai Bay Basin

If the site at which receiver functions are constructed is filled by sediments, then the waveforms from these receiver functions are dominantly controlled by the sedimentary structures within the first few seconds after the direct P arrival. Based on this observation, waveform data collected at 44 temporary seismic stations have been used to image the sedimentary structure of the Bohai Bay Basin, a major continental petroliferous basin in Eastern China. An adapted hybrid global waveform inversion method was applied to the receiver functions to extract structural information beneath each of the stations. The derived S-velocity structure provides for the first time, a basin-scale seismic image of detailed sedimentary stratification. The sedimentary cover of the basin is about 2-12 km thick, consisting of Cenozoic, Mesozoic, and Paleozoic strata from top to bottom. The structural features presented in the S-velocity image coincide quite well with the depression-uplift type of tectonic system in the Bohai Bay Basin. The reconstructed morphology of the sedimentary layers provides seismological evidence for the two-stage evolution of the intracontinental basin that were caused by an intensive tectonic regime transition in late Mesozoic immediately following the lithospheric reforming of the Eastern China continent.     

Distribution and ecological relevance of fine sediments in organic-enriched lagoons: the case study of the Cabras lagoon (Sardinia, Italy)

In organic-enriched sedimentary systems, like many Mediterranean coastal lagoons, a detailed analysis of sediment grain size composition and partitioning within the muds is crucial to investigate sedimentological trends related to both hydrodynamic energy and basin morphology. In these systems, sediment dynamics are particularly important because the partitioning and transport of fine sediments can strongly influence the redistribution and accumulation of large amounts of organic matter, and consequently the distribution of benthic assemblages and the trophic status and functioning of a lagoon. Nevertheless, studies on benthic-sediment relationships have been based mainly on a rather coarse analysis of sediment grain size features. In muddy systems, however, this approach may impede a proper evaluation of the relationships and effects of the distribution of fine sediment and organic matter on the biotic benthic components. Here we show that the distribution of sedimentary organic matter (OM) and total organic carbon (TOC) in the Cabras lagoon (Sardinia, Italy) can be explained (i.e., predicted) as a function of a nonlinear increase in the amount of the cohesive fraction of sediments (< or = 8 microm grain size particles) and that this fraction strongly influences the structure, composition and distribution of macrobenthic assemblages. Even in such a homogeneously muddy system, characterized by "naturally" occurring impoverished communities, impaired benthic assemblages were found at < or = 8 microm, OM, TOC contents of about 77%, 11% and 3.5%, respectively. A review of studies conducted in Mediterranean coastal lagoons highlighted a lack of direct integrated analysis of sediment features and the biotic components. We suggest that, especially in organic-enriched coastal lagoons, monitoring programs should primarily investigate and consider the cohesive fraction of sediments in order to allow a better assessment of benthic-sediment relationships and ecological quality of the system.     

地层学的进展对盆地研究的意义

地层学是地质研究的基本问题.从传统地层学发展到地震地层学及层序地层学,地层学的研究发生了一个极大的飞跃.其重要意义可与板块学说的问世相比拟.地震记录仪器的更新换代,地震学和地震勘探技术的发展,是层序地层学得以诞生的基础之一.运用层序地层学理论和方法确切地识别沉积相、沉积环境,建立完整的沉积体系,预测油气的生储盖组合,更易追踪对比的目标层.因此,它对于盆地研究具有非常重要的意义.     

Assessing tectonic and climatic causal mechanisms in foreland‐basin stratal architecture: insights from the Alborz Mountains,northern Iran

The southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3‐km‐thick sequence of Miocene sedimentary rocks, constituting three basin‐wde coarsening‐upward units spanning a period of 10⁶ years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment‐provenance data to characterize the relationships between tectonically‐generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S > 1, typical of each basal unit (17.5–16.0, 13.8–13.1 and 10.3–9.6 Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S < 1 (13.8 and 13.8–11 Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra‐basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S < 1, at 11–10.3 Ma and 9‐6–7.6 Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically‐induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. Copyright © 2013 John Wiley & Sons, Ltd.     

南海西南次海盆NH973-1测线地震解释

针对973项目“南海大陆边缘动力学与油气资源潜力”2009年新采集的多道地震剖面NH973-1测线进行了研究分析,获得以下初步认识:(1)西南次海盆深海平原南端下伏巨厚沉积体,表明陆坡坡脚不是洋陆边界的位置,深海平原南端为陆壳分布区,也可解释为洋陆过渡带.这种情况在南海的洋陆边界确定过程中应加以考虑.(2)西南次海盆洋...     

Cenozoic tectonic and sedimentary evolution of southern Qaidam Basin,NE Tibetan Plateau and its implication for the rejuvenation of Eastern Kunlun Mountains

The Eastern Kunlun Mountains play an important role in the growth and eastward extrusion of the Tibetan Plateau. Tectonic and sedimentary study of the Cenozoic Qaidam Basin, especially the southern part, provides key evidence for understanding their evolution. Here we present evidence including isopach maps, seismic sections and sedimentary analysis of single well to illustrate the sedimentary development of the basin and the structural features of its southern margin. The Qaidam Basin extended across Qiman Tagh-Eastern Kunlun Mountains in the early Cenozoic and withdrew northward at ca. 35.5 Ma, and then buckled as an EW striking elliptical depression since ca. 14.9 Ma, with the main depocenter migrating eastward. Our results support the view that the Kumukol and Hoh Xil basins joined the Qaidam Basin in the early Cenozoic time and we propose the Eastern Kunlun Mountains uplifted in the mid-Miocene.     

Cenozoic stratigraphy and sedimentation history of the northern Philippine Sea based on multichannel seismic reflection data

Abstract To clarify the regional distribution and characteristics of the sedimentary deposits in the northern part of the Philippine Sea, multichannel seismic reflection surveys of 26 864 km in total length were performed. The seismic reflection data were interpreted and correlated with available Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) data and a general stratigraphic framework of the area was established. The sedimentary deposits in this area were divided into five layers; Units I, II, III, IV and V in ascending order. Their approximate geological ages are the Early Eocene, Middle to Late Eocene, Oligocene, Miocene and Pliocene‐Pleistocene, respectively. Seismic records were classified into three seismic facies, Facies A, B and C, on the basis of their characteristics. They were judged to represent pelagic and hemipelagic sediments of non‐volcanic origin, fine pyroclastic sediments and coarse pyroclastic or volcanic sediments, respectively, by comparing them with lithological data in the DSDP/ODP holes. From the thickness and facies distributions of these sediments, a sedimentary history in the area was reconstructed as follows. The oldest sediments in the study area, Unit I, interfinger with some parts of the Daito Ridge (acoustic basement) in the Minami Daito Basin. The geological age of the unit is estimated by microfossils in the sediment and supports the idea that this part of the Daito Ridge is composed of the Early Eocene oceanic basalt. Later, a fair amount of sediments were deposited in the Minami Daito Basin in the Middle to Late Eocene age. A large volume of volcanic materials was supplied from the Paleo‐Kyushu‐Palau Ridge in the Kita Daito Basin in the Eocene and Oligocene ages. The eastern part of the Shikoku and Parece Vela basins is characterized by volcanic sediments supplied from the Nishi Shichito and West Mariana Ridges in the Miocene age. However, pelagic and hemipelagic sediments prevail in the northern part of the Shikoku Basin in the Miocene or later. In short, the area of principal sedimentation has generally shifted from west to east through geological time, reflecting the evolution of the island arc systems with the same trend in the northern Philippine Sea.     

济阳坳陷东营凹陷早始新世构造体制转换与油气成藏

以东营凹陷孔店组和沙四段沉积建造和构造特征为研究对象,依托高精度三维地震反射资料,通过地震反射界面确认、沉积层厚度和构造形迹精细解剖、探讨了东营凹陷在早始新世构造变形的特点,指出孔店组晚期——沙四下段沉积期是区域应力环境发生大转折期,由此提出了油气勘探的“立交桥”式思路,勘探意义重大.     

南海东南部陆缘地壳结构特征及其构造意义

南海东南部海域沉积厚度较大,礁体发育,构造演化复杂,导致深部结构探测不清楚,制约了对南部陆缘地壳结构的认识.本文通过对新采集和重新处理的多道地震剖面解释,结合钻井、拖网资料,对浅部地层和构造进行约束,同时利用附近海底地震(OBS)测线的速度结构,对深部结构和界面解释约束;在此基础上,开展了重震联合反演,分析地壳密度空间分布特征,结合重力梯度特征对构造单元进行识别.通过对东西两条测线的上下和全地壳厚度、拉伸因子比较,发现南海东南部的东西部深部结构存在差异性;礼乐断裂可能是礼乐和郑和地块的分界,并控制了两个地块在南海扩张时期的相对运动.     

High-Resolution Seismic Characterization of Shallow Gas Accumulations in the Southern Shelf of Marmara Sea,Turkey

High-resolution seismic survey was conducted to investigate acoustic characteristics of gassy sediments along the southern shelf of the Sea of Marmara. The acoustic turbidity zones outlined within the study area are generally below 2–9 m (2-10 ms TWT) the seafloor whilst this vertical distance varies between 9 and 21 m (10–25 ms TWT) for acoustic blanket type reflections. The gassy sediments cover an area of sea floor of about 45, 110, and 75 km² in front of Gönen River, Kocasu River, and Gemlik Bay, respectively. The gassy sediments in the center of Gemlik Bay exhibited an elliptical geometry similar to its basin while the others have deltaic forms in front of the rivers. The sea bottom and near surface sedimentary units are made-up of organic-rich sediments, mostly transported by the southern rivers. The gas observed in sediments is thought to be of biogenic origin, which may be caused by degradation of organic matter in the sediment.     

Seismic wave velocities in the sedimentary cover of Poland: Borehole data compilation

A knowledge of seismic wave velocities in the sedimentary cover is of great importance for interpreting reflection and refraction seismic data, deep seismic soundings and regional and global seismic tomography. This is particularly true for regions characterized by significant thicknesses and a complex sedimentary cover structure. This paper presents the results of an analysis of seismic P-wave velocities in the sedimentary cover of Poland, a complex area of juxtaposition of major tectonic units: the Precambrian East European Craton, the Palaeozoic Platform of Central and Western Europe, and the Alpine orogen represented by the Carpathian Mountains. Based on vertical seismic profiling data from 1188 boreholes, the dependence of velocity versus depth was determined for regional geological units and for successions from the Tertiary and Quaternary to the Cambrian. The data have been approximated by polynomials, and velocity-depth formulas are given down to 6000 m depth. The velocities in the sedimentary cover have been compared with those from other areas in Europe.