准噶尔盆地玛湖凹陷三叠系源上砂砾岩扇—断—压三控大面积成藏模式

准噶尔盆地玛湖富烃凹陷下三叠统百口泉组新近发现了我国首个源上大面积连续型砂砾岩油藏群,是对全球"连续型"油气藏研究的新补充,但其成藏机理和模式并不很清楚。为加强对其的理论认识,并为下步勘探提供参考,基于油气生、储、盖、圈、运、保等基础石油地质条件,并结合油气藏特征,进行了成藏条件与成藏模式的综合研究。结果表明,优质充足的下二叠统风城组碱湖油气来源、规模有效的扇三角洲前缘砂砾岩储层、多重组合的扇三角洲平原致密砾岩、泥岩和断裂封盖保存、沟通良好的高角度断裂输导体系、平缓连续的构造背景奠定了大面积连续成藏的地质基础。在此背景下,高成熟的风城组所生成油气,在切穿烃源灶和储层的高角度压扭性断裂沟通下,优先充注物性相对好的扇三角洲前缘水下河道砂岩和砂质细砾岩,并且在地层异常高压促进下,控制着油气富集程度,使得油气成藏表现为大型缓坡浅水扇三角洲沉积控制下的源上扇-断-压三控大面积"连续型"。百口泉组油气藏具有的油质轻且含气、微裂缝广泛发育,以及异常高压等,决定了砾岩储层虽总体低孔低渗,但依旧能够高产。在油源断裂沟通的斜坡区上倾方向,叠合地层异常高压以及扇三角洲前缘水下河道砂砾岩的区域是下步有利勘探方向。     

湖南常德南斗姆湖地区早更新世砾石层砾组分析与沉积特征研究

为了查明洞庭盆地西缘早更新世砾石层沉积特征及沉积环境,在1:5万地质调查基础上,对常德南斗姆湖地区几处第四系砾石层剖面进行了较系统的测量与统计。结果表明: 砾石成分主要来源于寒武纪或前寒武纪地层。砾石分选系数S_a 为1.16~1.64,部分测点S_a>1.40,反映砾石形成时水动力很强,部分砾石层为快速堆积。砾石扁度F为2.06~2.32,大于2.0,砾石以扁平状为主。砾石普遍弱—中等风化,部分砾石强风化,反映砾石在沉积搬运过程中存在风化暴露。砾向分析显示古水流主要来源于SWW—NW向,表明砾石层形成时期古地貌与现有地貌有较大差异。剖面对比得出,区内砾石层是在冲洪积扇基础上发育的以辫状河相为主的沉积体。对研究区砾石层沉积相及古地貌的新认识,为区内金刚石原生矿床的找矿工作提供支撑。     

海盆沉积“源-汇”系统分析:南海北部珠江海谷-西北次海盆第四纪深水浊积扇

运用近年来采集的高分辨率地震资料和多波束测深数据,在珠江海谷及西北次海盆深海平原区发现大规模发育的第四纪重力流沉积体系,该沉积体系沿珠江海谷以北西-南南东方向贯穿整个北部陆坡,进入西北次海盆后呈扇形展开,形成珠江海谷-西北次海盆大型深水浊积扇系统。据沉积体系空间展布特征差异,将珠江海谷划分为北、中、南三段,北段为过路侵蚀和水道下切,中段以水道充填和天然堤沉积为主,南段以水道-天然堤和朵叶体沉积共存为特征,揭示出北部陆坡珠江海谷是珠江口外陆缘物质输送海盆深海平原的主要通道;海盆区总体以朵叶体发育为特色,呈扇形展布。深水扇系统可分为三期次沉积体,其区域结构记录了重力流沉积物从侵蚀、卸载到南海海盆作为限制性盆地接收陆源沉积物的全过程,为“源-渠-汇”的研究构建了一个完美的范例。本文以珠江海谷-西北次海盆第四纪深水浊积扇沉积体系为例,完整地揭示了水道-扇体的组构和特征,清晰呈现了陆坡-海盆砂体展布的规律,可为建立南海北部新近纪早期深水扇形成模式提供参考,有助于指导南海深水油气勘探工作。     

A comparison of the effectiveness of the roots of two grass species in reducing soil erosion on alluvial fans in south-east China

The effects of root systems on soil detachment by overland flow are closely related to vegetation types. The objective of this study was to quantify the effects of two gramineous roots (Paspalum mandiocanum with shallow roots and Pennisetum giganteum with deep roots) on soil detachment capacity, rill erodibility, and critical shear stress on alluvial fans of benggang in south-east China. A 4-m-long and 0.12-m-wide flume was used. Slope steepness ranged from 9% to 27%, and unit flow discharge ranged from 1.39 × 10⁻³ to 4.19 × 10⁻³ m² s⁻¹. The mean detachment capacities of P. mandiocanum and P. giganteum lands were 18% and 38% lower than that of bare land, respectively, and the effects of root on reducing soil detachment were mainly reflected in the 0- to 5-cm soil layer. The most important factors in characterizing soil detachment capacity were root length density and soil cohesion, and soil detachment capacity of the two grass lands could be estimated using flow shear stress, soil cohesion, and root length density (NSE = 0.90). With the increase in soil depth, rill erodibility increased, whereas shear stress decreased. The mean rill erodibilities of P. mandiocanum and P. giganteum lands were 81% and 61% as much as that of bare land, respectively. Additionally, rill erodibilities of the two grass lands could be estimated as an exponential function by root length density and soil cohesion (NSE = 0.88). The mean critical shear stress of P. mandiocanum and P. giganteum lands was 1.29 and 1.39 times that of bare land, respectively, and it could be estimated with a linear function by root length density (NSE = 0.76). This study demonstrated that planting of the two grasses P. mandiocanum and P. giganteum could effectively reduce soil detachment and enhance soil resistance to erosion on alluvial fans, with the deep roots of P. giganteum being more effective than the shallow roots of P. mandiocanum. The results are helpful for understanding the influencing mechanism of root systems on soil detachment process.     

恒河深海扇东北区域晚第四纪气候和海平面变化对沉积作用的控制

通过对恒河深海扇沟道间均质细粒沉积物的氧同位素地层划分,本文讨论了晚更新世以来冰川—气候旋回和海平面变化对印度洋北部大陆坡地带各种活跃的沉积因素（陆源和碳酸盐物质的沉积通量、浊流活动的强度和频度、粘土矿物分布、碳酸盐浓度和钙质生物壳的溶解度）的控制作用和因素间的相互关联。     

广丰松峰盆地的扇三角洲特征

本文通过对盆地岩性组合和沉积的构造特点的分析,得出丰松峰盆地的沉积体系为扇三角洲。     

湖盆扇三角洲河口坝发育程度及粒度韵律特征:以滦平盆地桑园剖面下白垩统西瓜园组为例*

扇三角洲作为重要的油气储集场所,其成因单元类型及分布特征控制着油气的差异分布及采出效率。关于扇三角洲分流河道沉积特征已有共识,但河口坝沉积特征尤其是韵律特征尚存在争议。以滦平盆地桑园剖面下白垩统西瓜园组湖盆扇三角洲沉积体为例,通过人工实测及无人机观测相结合的方法,对河口坝沉积特征、尤其是韵律特征进行研究,利用水槽模拟实验阐明河口坝韵律特征的形成机理。结果表明,河口坝在整个剖面中占砂(砾)岩体的45.27%,分流河道和席状砂分别占53.42%和1.31%。河口坝在剖面上呈底平顶凸状,通常由多期增生体组成。当增生体主要由砂岩组成时,呈粒度反韵律特征; 而当增生体主要由砾岩组成时,呈粒度正韵律特征。河口坝整体韵律受控于增生体的垂向叠置样式,既可呈反韵律特征又可呈正韵律特征。当流量、沉积底形坡度等地质条件一定时,河口坝内部增生体韵律性主要受沉积物粒度控制。当沉积物粒度较细时,河口水流扩散模式为底床摩擦力主控,增生体呈现反韵律特征; 而当沉积物粒度较粗时,河口水流扩散模式为惯性力主控,河口坝增生体则呈现正韵律特征。     

RIVERS' FEATURES ON ALLUVIAL FANS IN NORTHWEST CHINA

IINTRODUCTIONAlluvialfanisakindofsedimentogeniclandform,whichisdevelopedwhereriverflowsoutofmountain.Holdingapositionalongfootsofmostmountains,itconstittltestheimportantpartofthefluvialsedimentarysystem.Hooke(1967)describedtraditionalriverformonalluvialfans.Riversinciseandformdeepstableandunstablechannelsonupperpartsofalluvialfans.Andbelowtheintersectionpoints,riversflowoutofthevalleysinformofbraidedchannelanddepositsmallsecondaryajlluvialfansonthesurfaceofthefan.Lobeck(1939,fromRochocki…     

古冲沟冲积扇体地震反射资料研究

利用地震资料研究古冲沟冲积扇体的反射特征、内部结构、剖面特征和分布特征等问题,研究结果为识别和确认古冲沟冲积扇体油气藏提供依据     

Late Eocene–early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

There are many large-scale Cenozoic sedimentary basins with plentiful river deltas, deep-water fans and carbonate platforms in the southern South China Sea. The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene, and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area. However, systematic analyses are still lacking regarding its sediment composition and potential source suppliers. No consensus has been reached yet on the provenance evolution and sedimentary infilling processes, which seriously impeded the oil-and-gas exploration undertakings. By combining with sedimentary-facies identification, heavy mineral assemblages, elemental geochemistry and detrital zircon U-Pb dating, this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan. In general, the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity. The continual southward subduction of the proto-South China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo. The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts. From the late Eocene to the early Miocene, the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland. The Zengmu Basin was widely deposited with delta plain and neritic facies sediments, while the Brunei-Sabah Basin, to the farther east, was ubiquitously characterized by turbiditic sequences. The Crocker Fan successions are overall thick layers of modest-grained sandstones, which formed high-quality reservoirs in the southern South China Sea region.