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Although CO2 storage has been comprehensively investigated, fewer scholars have taken the effect of temperature and the dual-porosity structure of coal into account, which brought a large deviation for the study of CO2 storage. In this work, a hydraulic-mechanical-thermal coupled model of CO2 storage is established, considering the dual-porosity structure features and non-isothermal adsorption of coal. The controlled variable method was used to simulate CO2 injection into coalbed with different characteristic parameters. The results show that the CO2 storage rate follows the law of first reducing and then stabilizing. The variation of permeability is a competition result of two types of factors: one is the coal matrix shrinkage caused by pressure increase and the other is the coal matrix expansion caused by the increase of temperature and CO2 adsorption. In the process of CO2 injection into the coal seam, the matrix expansion caused by the increase of temperature and CO2 adsorption becomes the dominant role, which makes the permeability reduce with time. The higher the initial temperature of coal seam, the less the volume of CO2 adsorbed by the unit mass of coal and the smaller the CO2 storage rate; the greater the degree of coal fracture development, the greater the CO2 seepage rate, the smaller the CO2 storage rate, and the increased volume strain of coal, which can reduce the storage rate of CO2. The initial temperature of coalbed, fracture development degree, and geostress have different degrees of influence on CO2 storage. Taking CO2 storage rate as an evaluation criterion, the fracture development degree has the greatest impact on it, and the influence of geostress is the least. [ABSTRACT FROM AUTHOR]

Although multi-branch horizontal well coalbed methane (CMB) extraction has been comprehensively investigated, fewer scholars have taken the effect of temperature into account, which brought a large deviation for the study of multi-branch horizontal well parameter design. In this work, the hydraulic-mechanical-thermal coupled model of multi-branch horizontal well CMB extraction was established. In order to verify the accuracy of the model and study the effect of temperature on CMB extraction, a series of numerical simulations based on engineering geological conditions and drilling arrangement parameters of 24307 face of Shaqu Mine were made, results show that: The CH4 production rate of both field data and numerical simulation result have the same changing tendency, and the difference between the simulation result and the actual value is not big. In multi-branch horizontal well CMB extraction process, the matrix shrinkage caused by temperature reduction and methane desorption dominates, the permeability continues to increase. Due to the effect of temperature on the amount of gas adsorbed by coal, the CH4 production decreases with the increase of initial reservoir temperature, and the permeability of coalbed increases with the increase of temperature. [ABSTRACT FROM AUTHOR]