Reservoir Evaluation and Development ›› 2022, Vol. 12 ›› Issue (1): 215-232.doi: 10.13809/j.cnki.cn32-1825/te.2022.01.019

• Shale Oil • Previous Articles     Next Articles

Outcrop characteristic and lithofacies changes of both Gufeng and Dalong Formations in lower Yangtze Region

YAO Suping1(),WU Yuyuan2,YU Wenduan2,ZHANG Bailin1,HU Wenxuan1   

  1. 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China
    2. Sinopec East China Oil and Gas Company, Nanjing, Jiangsu 210019, China
  • Received:2021-10-07 Online:2022-02-26 Published:2022-03-24

Abstract:

The Middle-Upper Permian Gufeng Formation and Dalong Formation are the important target horizons for the source rock exploration in South China. However, due to the obvious lithologic changes in both spatial and temporal distributions, there is still great controversy in the division and comparison of the regional stratigraphy, which restricts the exploration and potential evaluation of oil and gas resources. Thus here we analyzed six typical field outcrops of the Gufeng and Dalong Formations in the Lower Yangtze region and summarized their lithostratigraphic characteristics. By the regional comparison, we further analyzed their vertical and lateral lithofacies distribution. Combined with the geochemical parameters such as total organic carbon(TOC) content, the exploration potential of shale oil and gas is discussed. The results show that the lithological thickness of the Gufeng Formation in the Lower Yangtze region varies greatly, showing the characteristics of alternating thick and thin, and its deposition center is generally located in the areas of Fanchang-Wuhu and Jurong-Lishui. The Gufeng Formation can be basically divided into three members, among which the middle member with interbedded chert and siliceous mudstone is regionally stable and thick. The thickness of the Dalong Formation does not change much regionally, but it is affected by the paleogeographical setting. The lithological differentiation of the Dalong Formation is obvious in the region, and its chert and siliceous mudstone is mainly developed in the southern Anhui area, while in the northern Jiangsu area, it changes to shale. Based on the previous studies, it is suggested that the Gufeng and Dalong Formations of the Lower Yangtze region have high TOC contents, good organic matter types, and their maturity is generally within the gas generation range, indicating that they have great shale gas potential. The vertical distribution characteristics of the TOC in the Gufeng and Dalong Formations indicate that their middle-upper member is a more favorable horizon for shale gas exploration. Regionally, the Wuwei Basin, Jurong-Nanling Basin, Changzhou-Xuanguang Basin and Wuxi-Suzhou area are the relatively favorable areas for shale gas exploration; the Xuanguang-Meishan Basin and the Jurong Danyang-Huangqiao-Taizhou area have shale oil exploration prospects due to their low maturity.

Key words: Gufeng Formation, Dalong Formation, lithofacies, shale oil and gas, Lower Yangtze region

CLC Number: 

  • TE122