石油学报 ›› 2016, Vol. 37 ›› Issue (7): 855-866.DOI: 10.7623/syxb201607004

• 地质勘探 • 上一篇    下一篇

莺歌海盆地东方区黄流组重力流砂体的底流改造作用

黄银涛, 姚光庆, 朱红涛, 周锋德   

  1. 中国地质大学构造与油气资源教育部重点实验室 中国地质大学资源学院 湖北武汉 430074
  • 收稿日期:2015-12-22 修回日期:2016-05-03 出版日期:2016-07-25 发布日期:2016-07-28
  • 通讯作者: 姚光庆,男,1964年12月生,1985获武汉地质学院学士学位,1999年获中国地质大学(武汉)博士学位,现为中国地质大学(武汉)资源学院教授、博士生导师,主要从事储层地质学教学及相关研究工作。Email:gqyao@cug.edu.cn
  • 作者简介:黄银涛,男,1989年1月生,2011年获长江大学学士学位,现为中国地质大学(武汉)博士研究生,主要从事油气储层地质研究工作。Email:huangyintao@hotmail.com
  • 基金资助:

    中海石油(中国)有限公司湛江分公司项目"东方13-1/2气田储层沉积相精细研究"(CCL-2013-ZJFN1012)资助。

Reworking of gravity flow sandbody by bottom-current from Huangliu Formation in Dongfang area of Yinggehai Basin, northwestern South China Sea

Huang Yintao, Yao Guangqing, Zhu Hongtao, Zhou Fengde   

  1. Key Laboratory of Tectonics & Petroleum Resources of the Ministry of Education, China University of Geosciences; Faculty of Earth Resources, China University of Geosciences, Hubei Wuhan 430074, China
  • Received:2015-12-22 Revised:2016-05-03 Online:2016-07-25 Published:2016-07-28

摘要:

莺歌海盆地东方区上中新统黄流组一段为浅海重力流沉积,但浅海环境下水动力能量和方向十分复杂,关于重力流砂体的沉积过程和成因机制等方面还存在争议,特别在是否具有底流改造作用方面争议较大,故基于岩心、铸体薄片、测试数据以及元素地球化学数据对研究区底流改造作用进行识别,并探讨底流对重力流砂体的改造作用过程。底流改造作用的证据主要表现在:1垂直重力流方向,底流改造作用造成砂体展布范围更广;岩心上具有典型牵引流沉积构造特征,表现出波纹交错层理、脉状层理、S型交错层理,泥质条带可呈现丘形,细砂岩向上显示突变接触,且其内部具有弱侵蚀和截切构造特征,局部发育悬浮沉积泥质;2岩石成分、粒度特征及物性方面,由于底流的改造作用,其跳跃组分明显增加,细砂岩中泥质含量减少,粒度变大,底流改造砂岩平均孔隙度19.2 % ,平均渗透率106.9 mD,平均孔喉半径8.34 μm,使其物性明显好于重力流砂岩,且底流改造砂岩的有孔虫生物壳体多被破坏,而重力流砂岩的生物壳体大多保留完整;3砂岩元素地球化学特征方面,B/Al、Cr/V、Co/Ni及稀土元素指标均反映存在富氧水团的底流作用改造。综合区域演化特征可知,研究区存在内波内潮汐发育的基本条件,在重力流砂体沉积后不久,底流主要是对早期重力流厚砂体的上部进行改造,将原始重力流砂体中的泥质等细粒组分带走,使其孔喉半径增大,物性变好。底流改造砂体可作为优质储层,对后期开发具有重要实际意义。

关键词: 莺歌海盆地, 东方区, 黄流组, 重力流, 底流

Abstract:

The sandbody in upper Miocene Huangliu Formation from Dongfang area of Yinggehai Basin are shallow-marine gravity flow sediments. However, there are some controversies on the sedimentary process and genetic mechanism of gravity flow sandstone (GFS) due to the quite complex hydrodynamic energy and direction in shallow-marine environment, especially a big debate on that whether there is reworking of GFS by bottom-current in study area. Therefore, this paper indentified the reworking of GFS by bottom-current using seismic data, core, casting sections, measured data and whole-rock geochemistry data, and the process of reworking by bottom-current was also discussed. The evidences for the reworking of GFS by bottom-current are shown in the following aspects:(1) the bottom-current reworked sandstone (BCRS) has a more wide distribution perpendicular to the gravity flow direction; the core is characterized by typical traction-current sedimentary structures such as ripple bedding, flaser bedding, S-shaped cross bedding. Hummocky pelitic strip can also be found. The fine-grained sandstone show sharp upper contacts, internal weak erosional truncation surface, and suspension mud is locally developed. (2) In terms of rock components, grain size characteristics and physical properties, the leaping components increase markedly, while the mud content of fine-grained sandstone is reduced with grain size increasing from the BCRS due to the reworking of bottom current. After reworking of bottom current, the sandstones have the average porosity of 19.2 % , average permeability of 106.9 mD, and average pore-throat radius of 8.34 μm, indicating that they have significant better physical properties than GFS. Meanwhile, foraminifera shells of the BCRS are commonly damaged, but those of GFS are mostly preserved well. (3) In terms of elemental geochemistry in sandstone, the ratios of B/Al, Cr/V, Co/Ni and rare earth element (REE) index suggest the occurrence of reworking by oxygen-rich water mass. According to the regional evolution of Yinggehai basin, it can be found that there are basic conditions for the development of internal wave and internal tide in study area. The bottom-current mainly reworked the upper part of thick GFS shortly after the deposition, winnowing away of fine compositions such as original argillaceous component, resulting in larger pore throat radius and better physical properties. As a kind of high-quality reservoir, the BCRS have an important significance on development.

Key words: Yinggehai Basin, Dongfang area, Huangliu Formation, gravity flow, bottom current

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