Characteristics and main controlling factors of pore structures in low thermal maturity continental shale of Jurassic, northern Qaidam basin
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    Abstract:

    In order to study and identify the main controlling factors of the microscopic pore structuresin the low thermal maturity continental shale of Jurassic in the northern Qaidam Basin, the high- pressure mercury intrusion, low- temperature nitrogen adsorption, low- temperature carbon dioxide adsorption, nuclear magnetic resonance and other testing methods were used onshale samples from different depths in the same well. Finally, the full- scale quantitative and comprehensive characterization of pore structure can be realized. The results show that under the present low thermal maturity conditions, the pore size distribution of shale is multi- modal, the total pore size is mostly less than 25 nm, in which the main pore volume and specific surface area are mainly composed of 0. 4 nm micropores and 2~3 nm mesopores,most of the pores are parallel plates or inclined plates with slit- like pores. At present, due to the low maturity of organic matter, the pore volume of macropores is negatively correlated with the burial depth, positively correlated with TOC and clay mineral content.The pore volume of mesopores is negatively correlated with brittle mineral content, the pore volume and specific surface area are positively correlated with R o.The pore volume and specific surface area of micropores are positively correlated with TOC and brittle mineral content. The development of different pores in continental shale is mainly controlled by one or more factors such as burial depth, TOC, R o, brittle mineral content, clay mineral content, etc. With the increase of organic matter evolution degree, burial depth and brittle mineral content play a weak role in controlling pore development, and TOC, R o and clay mineral content become the main influencing and controlling factors of pore development and evolution.

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ZHANG Yunpeng, LI Yuhong, GUO Wang, HAN Wei, LI Yonghong, WANG Weichao.2021. Characteristics and main controlling factors of pore structures in low thermal maturity continental shale of Jurassic, northern Qaidam basin[J]. Acta Geologica Sinica,95(2):565-577

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History
  • Received:March 08,2020
  • Revised:October 12,2020
  • Adopted:October 12,2020
  • Online: October 23,2020
  • Published: