Characteristics and main controlling factors of water vapor adsorption in marine shale：A case study of the Lower Silurian Longmaxi shales in southern Sichuan Basin

被引：0
作者：
Zhang Y. [1 ]
Hui D. [2 ]
Zhang J. [1 ]
Zhang D. [1 ]
Jiang R. [1 ]
机构：
[1] Shale Gas Research Institute, Southwest Oil & Gasfield Company, PetroChina, Sichuan, Chengdu
[2] Exploration and Development Research Institute, Southwest Oil & Gasfield Company, PetroChina, Sichuan, Chengdu
来源：
Oil and Gas Geology | 2022年 / 43卷 / 06期
关键词：
Longmaxi Formation; mineral composition; pore structure; shale; Sichuan Basin; water vapor adsorption;
D O I：
10.11743/ogg20220612
中图分类号：
学科分类号：
摘要：
All shales contain a certain amount of water，and in-depth understanding of the occurring mechanism of water in shale pore system is of great significance to the efficient development of shale gas. Typical shale samples taken from the Lower Silurian Longmaxi Formation in the southern Sichuan Basin are applied to quantitatively study the occurrence characteristics of water in shale pores and analyze the main factors controlling water adsorption within shales. The study is carried out by means of the isotherm adsorption and desorption curves of vacuum water vapor generated by gravimetric adsorption instrument，coupled with parameters of shale compositions and pore structures. The results indicate that the isothermal curves of water vapor adsorption for the shale samples present three typical stages：single-layer adsorption，multi-layer adsorption and capillary condensation. The water vapor hysteresis loop can be divided into two stages of the“convex type”in medium-low relative pressure stage and the“flat type”in the whole relative pressure stage. The formation of the hysteresis loop in medium-low relative pressure zone mainly lies in reluctant interlayer dehydration of clay minerals. GAB and FHH models can effectively describe the characteristics of the adsorption curves. Furthermore，there is a significant positive correlation between the clay mineral content and the water adsorption amount，and it is believed that the strong hydrophilic property of clay minerals is the main factor controlling the amount of water vapor adsorption. While a negative correlation between carbonate mineral content and the water adsorption amount is observed. High carbonate mineral content is not conducive to the occurrence of water. For organic-rich shales，the adsorption capacity of water vapor has a strong correlation with the TOC content. Inorganic minerals and organic matter components jointly control the occurrence behavior of water molecules. The organic pores of kerogen can provide storage space for the adsorption of water molecules，and the larger the specific surface area and pore volume of the sample，the stronger the water adsorption capacity. However，for the clayey shale with low TOC content，the strong physicochemical interaction between clay minerals and water is key to large occurrence of water. © 2022 Editorial Department of Oil and Gas Geology. All rights reserved.
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页码：1431 / 1444
页数：13
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