Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (6): 1243-1254.doi: 10.11743/ogg20210601

• Petroleum Geology • Previous Articles     Next Articles

Petroleum systems and exploration potential in deep Paleogene of the Dongying Sag, Bohai Bay Basin

Mingshui Song1(), Yongshi Wang1, Xuefeng Hao2, Tianxia An2   

  1. 1. Shengli Oilfield Company, SINOPEC, Dongying, Shandong 257015, China
    2. Petroleum Exploration and Production Research Institute, Shengli Oilfield Company, SINOPEC, Dongying, Shandong 257015, China
  • Received:2020-03-27 Online:2021-12-28 Published:2021-12-16

Abstract:

The Dongying Sag is a representative non-marine faulted depression in the Bohai Bay Basin. Two wells (FSh1 1 and FShX 101) drilled into the deep of the sag were tested with high rates of oil flow, revealing great exploration potential of deeper layers that have been relatively overlooked during years of intensive oil and gas exploration and development in the basin. This study, taking the deep Paleogene strata in the sag as an example, aims to assess the potential through oil and gas accumulation models established on analyses of source rocks and genesis of high-quality reservoirs in the sag. The results show that the Ek (Kongdian Formation) and lower Es4 layers in the deep Paleogene constitute on their own an independent petroleum system. The source rocks in the Ek2 and lower Es4, developed in a saline lake (salinized) environment are characterized by an early, long and efficient hydrocarbon expulsion and a long hydrocarbon generation-expulsion cycle, providing key components for the formation of a deep petroleum system. The multi-type sedimentary facies of the saline lake have experienced alternative modification of acidic and alkaline diagenetic fluids, and formed high-quality reservoirs mainly composed of secondary dissolution pores, which provided good reservoir conditions for the deep hydrocarbon accumulation. The distribution of oil/gas reservoirs in the deep layers corresponds well to the structure of faulted depression, the development of sedimentary reservoirs and the dynamic system of hydrocarbon accumulation. The "indigenous" and "non-indigenous" hydrocarbon accumulation patterns are orderly distributed. Different types of oil/gas reservoirs, such as red beds and beach bar sandstone in gentle slope zone, as well as sandy conglomerate in steep slope zone, are the focus of exploration in the deep Paleogene of Dongying Sag.

Key words: hydrocarbon accumulation system, exploration potential, deep strata, Paleogene, Dongying Sag, Bohai Bay Basin

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