Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (1): 67-77.doi: 10.11743/ogg20190107

• Petroleum Geology • Previous Articles     Next Articles

Microscopic characteristics of pores in Es3 shales and its significances for hydrocarbon retention in Dongpu Sag,Bohai Bay Basin

Shao Xinhe1,2, Pang Xiongqi1,2, Hu Tao1,2, Xu Tianwu3, Xu Yuan1,2, Tang Ling1,4, Li Hui1,2, Li Longlong1,2   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China;
    2. College of Geosciences, China University of Petroleum(Beijing), Beijing 102249, China;
    3. Zhongyuan Oilfield Company Ltd., SINOPEC, Puyang, Henan 457001, China;
    4. Unconventional Natural Gas Institute, China University of Petroluem(Beijing), Beijing 102249, China
  • Received:2017-12-21 Revised:2018-10-10 Online:2019-02-28 Published:2018-12-08

Abstract:

The Es3 shales in Dongpu Sag were studied with XRD analysis,thin section and SEM observation,and low-temperature nitrogen adsorption experiment based on their basic geochemical characteristics.Microscopic characteristics of shale pores were analyzed,and thus controlling factors of shale pore development and its significance for hydrocarbon retention in shales have been identified.Results show:the Es3 shales in Dongpu Sag can be classified into silty shales,calcareous shales and gypsum shales according to their mineral compositions;the strong heterogeneity in shales'geochemical characteristics reflects a complex hydrocarbon retention pattern in Es3 shales;several pore types including interparticle,intraparticle and organic-matter pores and fractures,are identified in Es3 shales with different lithologies dominated by different pore types;the pore systems in Es3 shales can be dominated by micropores,macropores,or pores of multiple diameters based on low-pressure nitrogen adsorption experiment;pore development in Es3 shales is affected by both deposition and diagenesis,with deposition environment laying the foundation for pore development in various lithologies and diagenesis modifying pore structures during shale burial,respectively;oil and free gas mainly accumulate in large pores and microfractures,and micro-and meso-pores provide sites for adsorbed gas,while solution gas is of great significance to develop shale oil/gas resources.

Key words: shale, microscopic characteristic of pores, Es3, hydrocarbon enrichment, Dongpu Sag, Bohai Bay Basin

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