China Petroleum Exploration ›› 2023, Vol. 28 ›› Issue (4): 55-65.DOI: 10.3969/j.issn.1672-7703.2023.04.006

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Differences in geological characteristics and sweet spots evaluation of marine and continental shale oil: a comparative case study between Wolfcamp D shale oil in Permian Basin in north America and Gulong shale oil in Songliao Basin

Liu Yuxi1, Bai Bin1,Cao Jianzhi2,Wang Rui3,Zhu Rukai1,Meng Siwei1,Hou Xiulin1   

  1. 1 PetroChina Research Institute of Petroleum Exploration & Development; 2 Sinochem Petroleum Exploration & Production Co., Ltd.; 3 Research Institute of Exploration & Development, PetroChina Daqing Oilfield Company
  • Online:2023-07-14 Published:2023-07-14

Abstract: The global technical recoverable shale oil resources are 2512×108 t, and the cumulative crude oil output from shale series has reached up to 3.9×108 t in 2021, which has grown to be one of the major fields for global petroleum exploration and development. Based on the geological conditions and sedimentary characteristics, the “sweet spot” reservoir of continental shale oil in China is classified into three categories, i.e., interlayer type, mixed type and shale type, among which the interlayer type and mixed type shale oil are the main targets for global shale oil exploration and development. Recently, breakthrough has been achieved in the exploration of shale type shale oil. However, the sweet spot evaluation urgently needs to be deepened to provide a basis for achieving benefit shale oil development. Therefore, the geological characteristics between the Carboniferous Wolfcamp D marine shale oil in Permian Basin in north America and the Cretaceous Qingshankou Formation Gulong continental shale oil in China are compared, and the key indicators for sweet spot evaluation of shale type shale oil are discussed, so as to provide reference for the exploration and development of continental shale type shale oil in China. The comparative study indicates that the two sets of shales are dominated by felsic shale and clayey shale with high clay minerals and quartz contents, and show similar geological characteristics of formation overpressure, relatively light oil quality and high brittle mineral content; The reservoir space of Gulong shale oil is dominated by composite organic matter pores and bedding joints related to a large number of clay minerals, showing better connectivity than Wolfcamp D shale oil but slightly poorer organic carbon abundance. The geological sweet spot of Wolfcamp D shale includes organic-rich clayey shale and siliceous shale, while the engineering sweet spot is the organic-rich siliceous shale based on the fracturing results. Similarly, the geological sweet spot of Gulong continental shale oil includes organic-rich clayey shale and felsic shale by using evaluation indicator of retained hydrocarbon, and the engineering sweet spot is the silicic felsic shale.

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