Abstract：
The pore structure of shale determines the storage capacity of shale reservoirs. Therefore, studying the pore evolution
process of shale is of great significance in revealing the mechanism of shale gas enrichment. Previous systematic research work
has been carried out on the pore evolution process of marine shale, but relatively little research has been done on the pore evolu-
tion process of continental shale. This paper takes the low-maturity (
R
O
=0.65
%
) continental shale of the Qingshankou Formation
in the Songliao Basin as the research object. Through thermal simulation experiments, combined with gas adsorption, mercury
intrusion capillary pressure (MICP), X-ray diffraction (XRD) and other analysis, the evolution process of the pore structure of the
continental shale of the Qingshankou Formation in the Songliao Basin has been investigated. Systematic analysis, has established
the pore evolution model of this continental shale. The results show that as the degree of evolution increases, the pore volume
and specific surface area of shale undergoes a process of first increasing, then decreasing, and then increasing. The evolution of
pores is mainly controlled by organic hydrocarbon generation and clay mineral conversion. When 0.65
%
＜
R
O
≤
0.86
%
, kerogen
slowly generates hydrocarbons and combined with organic acid dissolution, some organic pores are formed, shale pore volume
and specific surface area increase slightly. When 0.86
%
＜
R
O
≤
1.18
%
, montmorillonite dehydration and new pore formation will
occur. This results in an increase in pore volume and specific surface area, but kerogen begins to generate a large amount of oil at
this stage, and the generated liquid hydrocarbons and asphalt will fill part of the original pores, making the shale pore volume and
specific surface area decrease. When 1.18
%
＜
R
O
≤
1.86
%
, the kerogen at the maturity-high maturity stage continues to generate
oil, but the rate of oil generation begins to decrease. At the same time, the kerogen begins to pyrolyze and form some gas
bubbles. And the bubbles further increase with the degree of evolution. During this period, the montmorillonite in the I/S (illite/
smectite mixed layer) transforms to illite. The three effects promote the increase of the pore volume and specific surface area
of micropores, mesopores and macropores. When
R
O
＞
2.15
%
, kerogen oil production stops, the liquid hydrocarbons generated
begin to crack and generate gas, forming a large number of bubble pores, and the pores further increase in the later period, The
phenomenon of pore fusion occurs, and at the same time, the conversion of montmorillonite to illite in I/S leads to a substantial
increase in pore volume and pore specific surface area
Key words：Songliao Basin; Qingshankou Formation; shale; thermal simulation; pore structure
Corresponding Authors： liudd@cup.edu.cn
Cite this article：李灿星, 刘冬冬, 肖磊, 姜振学, 李卓, 郭靖. 松辽盆地白垩系陆相页岩孔隙演化过程研究. 石油科学通报, 2021, 02: 181-195 LI Canxing, LIU Dongdong, XIAO Lei, JIANG Zhenxue, LI Zhuo, GUO Jing. Research into pore evolution in Cretaceous continental shales in the Songliao Basin. Petroleum Science Bulletin, 2021, 02: 181-195.
