莺歌海盆地黄流组大型高效储集体-浅海重力流沉积体的堆积机制研究

Large efficient reservoir-shallow marine gravity flow deposits of the Huangliu Formation in Yinggehai Basin, south China, which located at the central Dongfang area, represents its peculiarity in sedimentary features and deposit mechanism. The paleontology study of these gravity flow deposits indicates that the paleo water depth was 40-110m, which shows a shallow shelf environment. The gravity flow features include convolute deformation bedding and contemporaneous deformation structures. The vertical series are mainly Bouma sequence A and AB, which lack of Bouma CDE. The gravity flow deposits show the features of large scale, multiple phases (superposition of turbidite events and combination of vertical series), and sustainable development. The comprehensive genetic mechanism of the large gravity flow deposits that formed in shallow marine environments incudes: (1) continuously sources supply, (2) large-scale regression during the syndepositional period, (3) episodic dynamic and differential subsidence of shelf paleogeomorphology. The gravity flow deposits on the shallow marine shelf are the combined controlling results of source supply, tectonic activity, and relative sea level change, which represent highly coordinate relationship between these influence factors. Therefore, this study will focus on the macroscopic and macroscopic features, accumulation control factors, and particular mechanism of the shallow marine gravity flow deposits based on the research method and technique of tectonic-sequence stratigraphy, sedimentology, and geophysics exploration. Intensive study of these shallow marine gravity flow deposits show important theoretical value and practical significance for the theoretical research of large gravity flow deposits in shallow marine environment, and also provide reference for the frontier exploration of oil and gas.

位于莺歌海盆地中央的东方区黄流组发育大型高效储集体-浅海重力流沉积体的沉积特征和堆积机制具有其独特性。古生物研究表明，其沉积期的古水深在40-110m之间，属于陆架浅水沉积背景。其重力流特征表现有包卷变形层理、准同生变形构造等，主要发育鲍玛序列A段和AB段组合，缺失CDE段。对该重力流沉积体的初步研究表明，其具有大规模、多期次(浊积事件的垂向叠加序列组合)、持续性发育等特征，在浅海背景下形成大规模重力流沉积体的综合成因机制包括：(1)物源的持续供给，(2)同沉积期大规模海退作用，(3)陆架基底的幕式动态和差异性沉降。该重力流沉积体的发育受上述三大因素的联合控制。因此，拟采取构造-层序地层学、沉积学与地球物理勘探的系列技术与方法研究其宏观、微观特征及其堆积的控制要素与独特机制。该研究成果能丰富浅海区发育大型重力流沉积体的理论，对油气勘探新领域的拓展具借鉴价值。

位于莺歌海盆地中央的东方区黄流组发育大型高效储集体-浅海重力流沉积体的沉积特征和堆积机制具有其独特性。本研究采取了构造-层序地层学、沉积学与地球物理勘探的系列技术与方法来探讨其宏观、微观特征及其堆积的控制要素与独特机制。已揭示其沉积期的古水深在40-110m之间，属于陆架浅水沉积背景。重力流特征表现为包卷变形层理、准同生变形构造等，同时发育有鲍玛序列A段和AB段组合，缺失CDE段。整体上该浅海重力流沉积体具有大规模、多期次(重力流事件的垂向叠加序列组合)、持续性发育等特征，在浅海背景下形成大规模重力流沉积体的综合成因机制包括：(1)同沉积期大规模海退作用，(2)物源的持续供给，(3)陆架基底的幕式动态和差异性沉降。正是由于物源的持续性充足供应及浅海大陆架基底的幕式迅速动态沉降，造成陆架表面的坡度迅速增大，陆架局部的古地貌随之发生幕式动态变化，为沉积物在陆架上的沉积提供了有利条件，东方区的深凹背景为重力流沉积的发生提供了良好的堆积场所，从而触发了经过长距离搬运到陆架上的牵引流沉积在基底动态沉降的作用下发生重力流作用，在推进过程中经历了从前期牵引流渐变到后期重力流的动态沉积过程，形成大规模、持续性、多期次的重力流沉积。该研究取得的创新性认识有：(1)该研究成果丰富了对于浅海区发育大型重力流沉积体的理论认识以及沉积过程的精细解剖，得到了浅海大陆架作为大型重力流沉积体堆积并成为高效储集体发育场所的创新性认识；(2)沉积机制由牵引流向重力流发生转变的沉积过程改善了储层物性，使得该重力流沉积体成为高效优质储层，对油气勘探新领域的拓展具有重要的指导意义。