Shiyou shiyan dizhi (Nov 2022)

Differences in oil and gas enrichment in slope belts of rift basins and main controlling factors for hydrocarbon accumulation: a case study of Sanhe Sub-sag in Jinhu Sag, Subei Basin

  • Zuxian HUA,
  • Xiaoping LIU,
  • Biao SUN,
  • Tian LIU,
  • Jie LIU,
  • Qidong LIU,
  • Shili LIU,
  • Tianzhuo BI

DOI
https://doi.org/10.11781/sysydz202206950
Journal volume & issue
Vol. 44, no. 6
pp. 950 – 958

Abstract

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The slope zone of rift basin is close to the hydrocarbon generation center of deep depression zone, and is favorable area for oil and gas accumulation. Due to the heterogeneity of the development of fault and sedimentary system in slope zone, oil and gas accumulations often show obvious heterogeneity, and the degree and scale of oil and gas enrichment on the plane are different. The oil and gas accumulation of the second member of Funing Formation (E1f2) in the slope belt of Sanhe Sub-sag of Jinhu Sag of Subei Basin is characterized by rich in the south and poor in the north, and the hydrocarbon accumulation is controlled by multiple factors. Geochemical test and logging data interpretation showed that the southern part has better source conditions than the northern part in the study area. Three types of source-reservoir configurations were developed vertically: lower-sourced and middle-reserved, self-sourced and self-reserved, as well as upper-sourced and lower-reserved, among which the type of upper-sourced and lower-reserved is the most developed and has the most enriched oil and gas in the studied area. On the plane, there are three types of source-reservoir configurations: stacked source-reservoir type, source-reservoir adjacent type, and source-reservoir separated type. The northern part of the study area is dominated by the source-reservoir separation type, while the southern part is dominated by the stacked source-reservoir type and the source-reservoir adjacent type. The southern part of the study area has well-developed fault system, abundant provenance and sand bodies, while the northern part is far away from provenance and has underdeveloped sand bodies. It is concluded that the superior hydrocarbon source conditions, appropriate source-reservoir configurations and good transport system are the key factors controlling the enrichment of oil and gas in faulted basins.

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