Oil & Gas Geology ›› 2016, Vol. 37 ›› Issue (3): 422-432,438.doi: 10.11743/ogg20160316

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Classification and quantitative characterization of microscopic pores in organic-rich shale of the Shahejie Formation in the Zhanhua Sag,Bohai Bay Basin

Zhang Qin1,2, Zhu Xiaomin1,2, Li Chenxi1, Qiao Lijingyu1, Liu Chang3, Mei Xiaohan1, Du Huiyao4, Lu Jiajing4   

  1. 1. College of Geosciences, China University of Petroleum(Beijing), Beijing 102249, China;
    2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China;
    3. China United Coalbed Methane Corporation Ltd., Beijing 100011, China;
    4. The 1st Oil Plant of Dagang Oilfield, PetroChina, Tianjing 300280, China
  • Received:2016-01-20 Revised:2016-04-20 Online:2016-06-08 Published:2016-06-22

Abstract: It is a key step for reservoir evaluation and development of shale gas to analyze characteristics of the microscopic pores in organic-rich shale and quantitatively characterize their pore size distribution.Based on core description,thin section inspection,X-diffraction,SEM and nitrogen adsorption test,this paper analyzed mineral components,classified microscopic pore types and also quantitatively characterized pore size in organic-rich shale samples of the Shahejie Formation in the Zhanhua sag,Bohai Bay Basin.The results show that the samples are characterized by high carbonate content and low clay content.According to their positions in the formation,genetic origin and occurrence,the reservoir spaces are divided into two types,namely pores and fractures,and their size classification criteria are determined.The pores consist of mineral matrix pores and organic pores.The fractures include structural,inter-bedded,over-pressure induced,diagenetic and organic shrinkage fractures.Nitrogen adsorption test mainly displays three types of curves which represent the spatial distribution of micropores,mesopores and macropores in the shale samples respectively.While nitrogen adsorption test mainly measures the mesopores and is relatively insensitive to other pore size types,SEM can reveal the characteristics of macropores much more clearly.It is suggested to further perform measurements of carbon dioxide adsorption,Nano-CT and mercury injection to quantitatively characterize the size and spatial distribution of the micropores and macropores in the shale.

Key words: nitrogen adsorption test, quantitative characterization of pore size, microscopic reservoir space, mineral component, organic-rich shale, Shahejie Formation, Zhanhua Sag, Bohai Bay Basin

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