In-situ stress response characteristics of CO₂ storage capacity in coal seam

Accurate estimation of CO₂ adsorption capacity in coal seam is a great significance to CO₂ storage technology, especially the influence of coal seam depth on CO₂ adsorption capacity. Through the design and development of loading coal adsorption experimental system, the adsorption isotherms of five kinds of coal samples under different loading conditions were tested. The results show that there will be residual stress in coal after loading/unloading, and the residual stress increases with the increase of loading force. With the increase of loading stress, the porosity decreases exponentially, while the CO₂ adsorption capacity decreases linearly. That is to say, the in-situ stress increases by 1 MPa（the buried depth increases by about 40 m）, and the CO₂ adsorption capacity in coal decreases by about 0.43% of the maximum adsorption capacity.