Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (3): 566-581.doi: 10.11743/ogg20220307

• Petroleum Geology • Previous Articles     Next Articles

Characteristics and reservoiring patterns of “teeth-brush-shaped” oil pools in the Shulu Sag, Bohai Bay Basin

Chuanbing Lyu1(), Xiongqi Pang2,3, Kuiyou Ma2,3, Hong Pang2,3, Xungang Huo2,3, Liangliang Fu1, Xingang Zhang2,3, Xingru Liang1,2, Song Wu2,3   

  1. 1.Huabei Oilfield Company,PetroChina,Renqiu,Hebei 062552,China
    2.State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum (Beijing),Beijing 102249,China
    3.College of Geoscience,China University of Petroleum (Beijing),Beijing 102249,China
  • Received:2021-01-11 Revised:2022-03-14 Online:2022-06-01 Published:2022-05-06

Abstract:

The Shulu Sag in Jizhong Depression possesses all the necessary factors for hydrocarbon to accumulate. However, many vertical wells drilled there failed to yield any industrial oil/gas flow. This paper takes the “teeth-brush-shaped” reservoirs in the Shahejie Formation, Checheng oilfield, Shulu Sag as study subject to crack the enigma. The characteristics, barrier bed features, cap rock features, oil and gas sources and migration paths for the reservoirs are investigated to analyze the conditions and process of hydrocarbon accumulation and summarize reservoiring patterns. The results shows that the “teeth-brush-shaped” oil pools occur with a high net-to-gross ratio, and adjacent oil pools are segmented into different pressure systems by cap rocks, while single oil pool is compartmentalized into a series of reservoir units of the same pressure system by relatively tight sandstone barriers. Faults were the major vertical and lateral migration pathways for hydrocarbon. Two stages of hydrocarbon charging occurred in the area with the first stage being the main contributor of hydrocarbons to the reservoirs. However, some of the hydrocarbons were dissipated while moving upward to the shallower layers along faults, resulting in a gradually thinning reservoirs with decreasing depth. With the migration direction roughly perpendicular to the distribution direction of reservoirs with dominant net-to-gross ratio, hydrocarbons tend to accumulate in fault traps along migration pathways, forming a series of “teeth-brush-shaped” oil pools. The genetic mechanism of the oil pools revealed by the study can be used as a reliable theoretical basis for subsequent exploration and development in the study area.

Key words: oil source conditions, reservoir characteristics, reservoir-seal assemblage, migration pathway, “teeth-brush-shaped” oil pool, reservoiring pattern, Shulu Sag, Bohai Bay Basin

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