石油学报 ›› 2014, Vol. 35 ›› Issue (4): 646-653.DOI: 10.7623/syxb201404004

• 地质勘探 • 上一篇    下一篇

南海北部珠江口盆地白云凹陷深水区重力流沉积机理

庞雄, 朱明, 柳保军, 颜承志, 胡琏, 郑金云   

  1. 中国海洋石油南海东部石油管理局 中海油深海开发有限公司 广东广州 510240
  • 收稿日期:2014-02-22 修回日期:2014-05-08 出版日期:2014-07-25 发布日期:2014-08-05
  • 通讯作者: 庞 雄,男,1962年4月生,1984年获西南石油学院学士学位,现为中国海洋石油总公司勘探专家、教授级高级工程师,长期从事珠江口盆地深水油气勘探研究。Email:pangxiong@cnooc.com.cn
  • 作者简介:庞 雄,男,1962年4月生,1984年获西南石油学院学士学位,现为中国海洋石油总公司勘探专家、教授级高级工程师,长期从事珠江口盆地深水油气勘探研究。Email:pangxiong@cnooc.com.cn
  • 基金资助:

    国家重大科技专项(2011ZX05025-003)、国家自然科学基金重点项目(No.91128207)和国家高技术研究发展 计划(863)项目(2013AA092600)资助。

The mechanism of gravity flow deposition in Baiyun sag deepwater area of the northern South China Sea

Pang Xiong, Zhu Ming, Liu Baojun, Yan Chengzhi, Hu Lian, Zheng Jinyun   

  1. CNOOC Nanhai East Petroleum Bureau/CNOOC Deepwater Development Limited, Guangdong Guangzhou 510240, China
  • Received:2014-02-22 Revised:2014-05-08 Online:2014-07-25 Published:2014-08-05

摘要:

根据近年的勘探实践,南海北部珠江口盆地白云凹陷深水区的优质储层主要为深水重力流砂岩沉积成因,探讨白云凹陷深水重力流的沉积机理是储层研究的基础。通过对深水重力流的流动机制和流变过程的理解以及白云凹陷深水重力流沉积结构的分析认为,陆坡区是深水重力流的主要沉积环境,陆架坡折带控制了白云凹陷深水重力流沉积的发育分布。南海北部宽陆架背景使得沉积作用更明显地受到海平面变化的控制,白云凹陷深水区主要的粗粒陆源碎屑重力流沉积与相对低海平面有关。高位末期古珠江三角洲推进到了陆架边缘,低海平面期间重力流沉积在白云凹陷深水陆坡区形成了平面上的多点源-线源的多水道-朵叶体散布,时间上有先后层次地周期性出现的沉积模式,这种沉积模式导致了砂岩储层分布的散布性、诡异性和形成岩性圈闭的复杂性。多水道化中小规模的复杂砂体分布是白云凹陷深水储层的特色。深水重力流具有沿坡搬运,下切成沟,坡缓减速,择低而积,稀释分异,有限分布等特点。重力流的流变过程中最重要的变化是在流动过程中被海水混入稀释而导致的砂、泥分异作用,这是砂泥混合重力流能够析出砂岩的过程。

关键词: 白云凹陷深水区, 重力流, 流态变化, 沉积机理, 陆架坡折带, 优质砂岩储层

Abstract:

In recent years, field exploration has demonstrated that high-quality reservoirs in Baiyun sag deepwater area of the northern South China Sea are mainly resulted from deposition of gravity flow sandstones. Exploring the mechanism of deepwater gravity flow deposits in the Baiyun sag deepwater area is thus the fundamental basis for research on relevant reservoirs. An analysis of flowing mechanism, rheological process, and depositional structure of deepwater gravity flows indicates that continental slope provided the major depositional environment where shelf break controlled the development and distribution of deepwater gravity flow deposits in the Baiyun deepwater area. The deposits of deepwater gravity flows were more obviously controlled by sea level change on the broad continental shelf of the northern South China Sea, and the major coarse-grained terrigenous gravity flow deposits were related to relatively low sea level in the Baiyun sag deepwater area. In the late highstand period, paleo-Pearl River delta moved forwards to the shelf margin, and in the lowstand period, gravity flows deposited on the continental slope of Baiyun sag deepwater area. These mechanisms led to planar distribution of scattered multipoint-linear source multichannel-lobes and successive, hierarchical, periodical model of deposition, which accounted for the scattered and strange distribution of sandstone reservoirs and the complexity of lithologic traps. Small-medium scale complicated multichannel sand bodies are characteristic of Baiyun deepwater reservoirs. The deepwater gravity flows feature transportation along slope, incision to channel, deceleration with gentle slope, accumulation in low place, differentiation under dilution, and limited distribution. The most important change in gravity flows during the rheological process is sand - mud differentiation as a result of sea water dilution during the flow process, which enables the process of sandstone separating from sand-mud mixed gravity flows.

Key words: Baiyun sag deepwater area, gravity flow, rheological process, sedimentation mechanism, shelf break, high quality sandstone reservoir

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