Oil & Gas Geology ›› 2023, Vol. 44 ›› Issue (4): 846-856.doi: 10.11743/ogg20230404

• Petroleum Geology • Previous Articles     Next Articles

Geological heterogeneity of shale sequence and evaluation of shale oil sweet spots in the Qingshankou Formation, Songliao Basin

Bin BAI1,2(), Chaocheng DAI3, Xiulin HOU1, Liang YANG4, Rui WANG2,5, Lan WANG1, Siwei Meng1,2, Ruojing DONG1, Yuxi LIU1   

  1. 1.Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China
    2.National Key Laboratory of Continental Shale Oil,PetroChina,Daqing,Heilongjiang 163453,China
    3.School of Earth Sciences,East China University of Technology,Nanchang,Jiangxi 330000,China
    4.Research Institute of Exploration and Development,Jilin Oilfield Company,CNPC,Songyuan,Jilin 138099,China
    5.Daqing Oilfield Co. Ltd. ,PetroChina,Daqing,Heilongjiang 163453,China
  • Received:2023-03-16 Revised:2023-06-28 Online:2023-08-01 Published:2023-08-09

Abstract:

The lacustrine sediment of the Cretaceous Qingshankou Formation in the Songliao Basin is rich in organic shale, and the well Guye 1 has achieved a breakthrough in oil exploration of Gulong shale of deep lake facies. To further evaluate the geological characteristics of the shale sequence in different facies zones of the lacustrine basin and evaluate the characteristics of shale oil sweet spots in the continental lacustrine basin, we study the geological heterogeneity of shale sequences in different facies zones of the lacustrine basin regarding the environmental difference for lacustrine shale formation in the Qingshankou Formation. It is suggested that the shale sequences deposited in the freshwater lacustrine basin can be divided into seven types according to lithofacies, namely the organic-rich lamellar clayey shale (TOC>3 %), lamellar clayey shale, felsic shale, lamellar shell shale, massive mudstone, limestone and dolomite respectively, which are evaluated in terms of total hydrocarbon generated and retained, hydrocarbon mobility, reservoir property, compressibility and oil production capacity. The geological and engineering sweet spots of shale oil are thereby proposed. Based on the contents of TOC and S1 (pyrolysis hydrocarbon content), we group the geological sweet spots of the Qingshankou Formation shale into TypeⅠ,Ⅱ, and Ⅲ. The TypeⅠ sweet spot is generally characterized by TOC content greater than 3 % and S1 greater than 4 mg/g; the Type Ⅱ by TOC content ranging between 1.5 % and 3 %, and S1 between 1.0 and 4 mg/g; the Type Ⅲ by TOC content less than 1.5 % and S1 less than 1.0 mg/g. The semi-deep lacustrine and deep lacustrine facies are dominated by sweet spots of TypeⅠ and Ⅱ, while the shales of shallow lacustrine facies by sweet spots of Type Ⅱ and Ⅲ. The Qingshankou Formation shale in Songliao Basin is selected as the major oil pay zone after a comprehensive analysis of the oil-bearing property, percolation coefficient, compressibility, characteristics of source rocks and physical properties of different facies zones.

Key words: geological sweet spot, engineering sweet spot, organic-rich shale, Gulong shale oil, Qingshankou Formation, continental lacustrine basin, Songliao Basin

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