doi:10.16186/j.cnki.1673-9787.2019120015

Received:2019/12/05

Revised:2020/02/05

Published:2021/07/15

Micro-pore characteristics and gas-bearing properties of marine continental transitional shale reservoirs in the Qinshui basin

MA Ruying1, ZHANG Jian1, WANG Meng1,3, MA Wenpeng1, ZHAO Jianguang1

1.College of Geology and Mining Engineering， Xinjiang University， Urumqi 830046 ， Xinjiang， China;2.Shaanxi Coalfield Geological Project Management Consulting Co. ， Ltd. ， Tongchuan  727000 ， Shaanxi， China;3.School of Resources and Earth Science， China University of Mining & Technology ，Xuzhou  221116 ， Jiangsu， China

Abstract:In order to more accurately characterize the physical properties and gas-bearing characteristics of the marine continental transitional shale reservoirs in the Qinshui basin， the shale of Shanxi Formation and Taiyuan Formation of Y3 well in Qinshui basin was taken as the research object. Through organic geochemical tests and scanning electron microscopy （ SEM） ， X-ray diffraction experiments， high-pressure mercury intrusion and low- temperature nitrogen adsorption experiments， combined with isothermal adsorption experiments and gas content tests， the physical property characteristics and gas bearing property of Carboniferous Permian shale reservoir in Y3 well were evaluated. The results showed that ： （1） The type of organic matter in shale was type III， and the content of total organic carbon （TOC） was relatively high. Among them， 84. 91% of the samples with TOC > 1 % had experienced high thermal evolution history， and the brittleness index was relatively low with an average of 40.5% ； （2） The pores of shale were well developed and contained many organic matter pores， intergranular pores， intragranular pores and microcracks. The fractal dimensions of some mesopores and macropores were medium and low with obvious fractal characteristics；（3）The contribution of mesopores to pore surface area and pore volume was greater than that of macropores. The clay mineral content had no obvious correlation with macropores and mesopores， but it was conducive to the development of macropore specific pore volume， mesopore volume and BET specific surface area ； quartz was not conducive to the development of macropore specific pore volume， and had a certain negative correlation with mesopore volume and BET specific surface area ； （4） The maximum adsorption capacity of the sample was low. Among which， both the TOC and illite were beneficial to the adsorption of gas， while the kaolinite played an inhibitory role in inhibition ；The clay minerals and quartz had no obvious relationship with Langmuir's volume on the whole ； （5） The total gas content of most samples was higher than the lower limit of shale gas industry development of0.5 cm3/g. The desorption gas and the total gas content were well correlated with the TOC， R₀ and kaolinite， while the illite tended to inhibit gas desorption ；On the whole， the clay minerals were negatively correlated with the desorption gas and total gas content ；The quartz content had a positive correlation with the desorption gas and total gas content ； The desorption gas content had a great positive correlation with the BET specific surface and pore volume of mesopores. This study had characterized the physical properties， micro pore characteristics， gas bearing characteristics and its influencing factors of shale reservoir， which had theoretical and practical significance for the geological research and development of marint continental transitional phase shale gas.

Key words:Qinshui basin;shale reservoir;microscopic pore characteristic;gas content

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