Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (2): 486-501.doi: 10.11743/ogg20240213

• Petroleum Geology • Previous Articles     Next Articles

Architectural characteristics of beach-bar reservoirs in the lower submember of the 2nd member of the Paleogene Dongying Formation in block SC7, Huanghekou Sag, Bohai Bay Basin

Changyin SHAO1(), Fan SONG1(), Shiqi ZHANG1, Qiuyue WANG2   

  1. 1.State Key Laboratory of Deep Oil and Gas,China University of Petroleum (East China),Qingdao,Shandong 266580,China
    2.Geological Research Institute of Binnan Oil Production Plant in Shengli Oilfield,Binzhou,Shandong 256600,China
  • Received:2023-12-03 Revised:2024-01-28 Online:2024-04-30 Published:2024-04-30
  • Contact: Fan SONG E-mail:2442704787@qq.com;songfan0026@163.com

Abstract:

Beach bars in block SC7 of the Huanghekou Sag, Bohai Bay Basin are identified as important reservoirs in the shore-shallow lacustrine area. Figuring out the internal structural characteristics of the beach-bar sand bodies can offer significant guidance for hydrocarbon exploitation. Based on the examination of modern analogs and data on cores and logs, we carry out architectural dissection for sand bodies in the lower submember of the 2nd member of the Dongying Formation (the Dong 2 lower submember) in block SC7, segmenting the beach-bar facies featuring thick mudstones and thin sandstones to five sedimentary microfacies: bar center, bar lateral margin, inner marginal beach, outer marginal beach, and lacustrine mud. By analyzing the origin and internal structural characteristics of the thick-mudstone and thin-sandstone beach bars, we investigate the sedimentary characteristics and pattern and growth process of the beach bars. Consequently, the beach-bar architectures are categorized into three levels, namely composite sand bar, single bar, and accretionary body, along with the exploration of the spatial distributions of these architectural units of beach bars. To identify single bars, we propose four indicators: inter-bar mudstone, logging curve characteristics, relative elevation difference, and lateral phase change of a single bar. Using these indicators, we identify single bars in the area with a dense well pattern, analyzing their scales, evolution process, and interconnectivity. Furthermore, four phases of accretionary bodies within single bars are determined, finally ascertaining the effects of 4th-level architectural interfaces, single-bar lateral phase change, and accretionary bodies within single bars on hydrocarbon distribution.

Key words: distribution pattern of single bars, architectural dissection, sedimentary microfacies, beach bar, Dongying Formation, Huanghekou Sag, Bohai Bay Basin

CLC Number: