【作者】 刘晖；

【导师】 姜在兴；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2011， 博士

【摘要】 大兴砾岩位于渤海湾盆地廊固凹陷西部大兴断层下降盘,其与大套成熟烃源岩相接触或为后者所包围,有着巨大的资源潜力。综合地震、测井、岩心、薄片等资料,对大兴砾岩的古地质背景、成因类型及其沉积特征进行了研究。大兴砾岩主要发育于盆地强烈断陷期,构造演化和断层活动对大兴砾岩的形成和分布具有明显的控制作用,前古近纪构造控制物源类型,古近纪构造控制了砾岩体的分布层系,大兴断层的幕式活动及迁移特征控制了砾岩体类型及演化。沙三下亚段沉积之前,大兴凸起上主要发育蓟县系白云岩、寒武系-奥陶系灰岩地层,局部发育中生界碎屑岩地层;沙三下亚段沉积之后,大兴凸起之上发育的地层主要为蓟县系白云岩和寒武系灰岩地层,奥陶系灰岩分布范围减小;沙三中亚段沉积之后,大兴凸起之上主要发育蓟县系白云岩地层,局部发育寒武系灰岩地层。在凸起古地质背景的控制下,大兴砾岩岩石类型以杂基支撑砾岩和颗粒支撑砾岩,砾石组分主要为白云岩和灰岩,沉积构造类型单一,主要以反映重力流沉积特征的块状层理和同生变形构造为主。在沉积背景研究的基础上,结合岩心相、地震相、测井相等,建立了三种主要的砾岩体成因模式。重力流水道主要由颗粒支撑砾岩和杂基支撑砾岩组成,在垂向层序上自下而上表现为主水道、次水道叠加的正韵律组合,在Sp、Rt曲线主水道表现为高幅的箱形,次水道表现为齿化箱形或钟形;在地震剖面上,重力流水道在横向上表现为楔状的下凹充填、具有侧积或近乎水平的上超结构,在纵向上体现为明显的前积结构。碎屑流近岸水下扇岩石类型主要为颗粒支撑砾岩,在垂向上自下而上依次发育内扇、中扇和外扇,表现为向上变细的正旋回水进序列,在测井曲线上表现为箱形或齿化箱形组合,具“低Gr、高Rt”的特征,在地震剖面上表现为强振幅的向湖盆延伸的楔状体。泥石流近岸水下扇主要的岩石类型为杂基支撑的砾岩,在垂向层序上,和碎屑流型近岸水下扇一样,也是自下而上表现为内扇-中扇-外扇的水进型沉积序列,在Sp和Rt曲线上表现为齿化的钟形或箱形组合,在地震剖面上,砾岩体内部表现为强振幅的杂乱反射特征,边缘与湖相泥岩反射呈指状接触,扇体向湖盆延伸范围较小。在砾岩组分、岩石结构、砾岩成因与相带等因素的控制下,砾岩体孔渗特征和油气产能由好到差分别为:碎屑流型近岸水下扇、重力流水道和泥石流型近岸水下扇,因此,三种砾岩体成因模式的建立,对于廊固凹陷大兴砾岩的精细勘探具有重要的现实意义。更多还原

【Abstract】 Daxing Conglomerate is located on the downthrown side of Daxing Fault in the westernLanggu Depression of Bohai Bay Basin. It is contacted or surrounded by a big set of maturehydrocarbon source rocks and has the huge resource potential. In this paper, the geologicalbackground, genetic types and sedimentary characteristics of the Daxing conglomerate in thethird member of the Oligocene Shahejie Formation (Es3) in the Langgu Depression werestudied in detail based on seismic profiler, logging, cores, petrographic thin-sections andscanning electron microscope (SEM) photos. Daxing Conglomerate was mainly developed inthe intensively faulting period of Langgu Depression. The structure evolution and faultactivity controlled the formation and distribution of Daxing Conglomerate. The pre-Paleogenetectonic movement controlled the source types of conglomerate, the Paleogene tectonicmovement controlled the vertical distribution of conglomerate, and the episodic activity andmigration controlled the genetic types and evolution. The stratum on the Daxing Bulge weremainly dominated by dolomites in Jixian System, Cambrian and Ordovician limestones andlocal Mesozoic clastic rocks before the deposition of the lower submember of the Es3. Thestratum on the Daxing Bulge were mainly characterized by dolomites in Jixian System,Cambrian limestones and local Ordovician limestones after the deposition of the lowersubmember of the Es3. The stratum on the Daxing Bulge were mainly dominated bydolomites in Jixian System and local Cambrian limestones after the deposition of the middlesubmember of the Es3. Under the control of geological background of Daxing Bulge, the rocktypes of Daxing Conglomerate were mainly matrix-supported conglomerates andgrain-supported conglomerates. The gravels in conglomerates were dominated by dolomitesand limestones. The sedimentary structures in conglomerates were simplex, which weredominated by massive bedding and contemporaneous deformation structure. Based on thedepositional setting, three genetic models of conglomerate, including gravity flow channel,grain flow nearshore subaqueous fan and mud flow nearshore subaqueous fan, have been setup depending on cores, seismic facies and electrofacies. The gravity flow channel wascharacterized by matrix-supported conglomerates and grain-supported conglomerates. Itshowed the positive sequence overlying by main channel and subchannel from bottom to topin vertical sequence. In logging caves, main channel was high amplitude box shape, and subchannel was in jugged box shape or bell shape in Sp and Rt caves. In seismic section, thegravity flow channel showed as wedgy filling with lateral accretion or nearly horizontal onlapstructure in cross section and obvious progradational reflection configuration on longitudinalsection. The grain flow nearshore subaqueous fan was dominated by grain-supportedconglomerates. In the vertical section, it was successively deposited by inner fan, middle fanand outer fan from bottom to top, showing the upward-fining retrogradation sequence. Inlogging caves, it showed as box shape or jugged box shape with characteristics of low Grvalue and high Rt value. In seismic section, it was the strong amplitude wedge set extendingto the centre of basin. The mud flow nearshore subaqueous fan was characterized bymatix-supported conglomerates. In the vertical sequence, it successively deposited by innerfan, middle fan and outer fan from bottom to top, showing the upward-fining retrogradationsequence like the grain flow nearshore subaqueous fan. In Sp and Rt caves, it showed asjugged bell or box shape. In seismic section, it showed as strong amplitude chaotic seismicreflection configuration with the border fingerlikly contacting with lacustrine mudstonereflection. Under the control of gravels, structure, genetic types and facies tract, theconglomerate bodies were grain flow nearshore subaqueous fan, gravity flow channel andmud flow nearshore subaqueous fan in poroperm characteristics and hydrocarbon productionfrom good to bad. Therefore, the establishment of three genetic models of conglomerate hasan important significance for fine exploration of oil and gas of Daxing Conglomerate inLanggu Depression.更多还原