Oil & Gas Geology ›› 2023, Vol. 44 ›› Issue (2): 441-451.doi: 10.11743/ogg20230215

• Petroleum Geology • Previous Articles    

Controlling effect of slope-break zone and paleovalley on sedimentation in rifted lake basins: A case study of the Paleogene Wenchang Formation in Haifeng 33 Subsag, Pearl River Mouth Basin

Zichen HE1(), Hao LIU1(), Heming LIN2, Xinwei QIU2, Xudong WANG2, Yongtao JU3, Xiaoming QUE2   

  1. 1.School of Ocean Sciences,China University of Geosciences,Beijing 100083,China
    2.Shenzhen Branch,CNOOC,Shenzhen,Guangdong 518000,China
    3.School of Mining Engineering,North China University of Science and Technology,Tangshan,Hebei 063210,China
  • Received:2022-08-01 Revised:2022-11-16 Online:2023-04-01 Published:2023-03-17
  • Contact: Hao LIU E-mail:3109596992@qq.com;lhcugb@163.com

Abstract:

Rifted lake basins usually have their sedimentary filling controlled by the intensity of tectonic activities, sea level fluctuation and sediment flux. The distribution of sand bodies in these basins are also controlled by slope-break zones and paleovalley systems. It is of great significance to explore the configuration relationship between the slope break zones and paleovalley systems for oil and gas exploration in rifted lake basins. The Pearl River Mouth Basin is the most important petroliferous basin in the South China Sea. The less explored Haifeng 33 Subsag in the basin is selected to study the factors controlling the development of sedimentary systems so as to support the mapping of reservoirs and deployment of oil and gas exploration. Based on 3-D seismic data and logging data of the subsag as well as on the basis of regional structural interpretation, this paper analyzes the types and development characteristics of the slope-break zones and the paleovalleys of the Paleogene Wenchang Formation in the subsag, and clarifies the control of the slope-break zones and paleovalleys on sediment filling. The results show that there are three types of slope-break zones in the study area: fault slope-break zone, flexure slope-break zone and sedimentary slope-break zone. The paleovalleys are mainly V-shaped, U-shaped, W-shaped and single fault groove types, among which the V-shaped and U-shaped valleys are more in number and more concentrated in-plane distribution. The slope-break zones control the boundary of denudation and provenance, thus mobilizing the sediments in a certain direction for a certain distance within certain space. Different sedimentary systems are believed to be developed in different periods under the influence of these zones. Serving as transport channels, paleovalleys control the direction of sediment transport, location of sediment discharge as well as scale of depositional system. It is concluded that slope-break zones together with paleovalleys determine the types, scales, development and evolution of depositional systems.

Key words: slope-break belt, paleovalley, paleogeomorphology, sedimentary system, regional structure, Wenchang Formation, Haifeng 33 Subsag, Pearl River Mouth Basin

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