Carbon dioxide (CO2)-enhanced coalbed methane recovery (CO2-ECBM) is a critical way to increase production and reduce greenhouse gas (CO2 CH4) emissions. As captured CO2 continuously injected in the coal seams, low cost of sequestration high efficiency CH4 can be achieved via flooding replacing effects driven by flow. Scientific insights into complex process CO2-ECBM experiments, modelings, technological developments need made propose appropriate countermeasures. This review first highlights...

Abstract The evolution of mining-induced stress field in longwall panel is closely related to the fracture and breaking characteristics strata. Few laboratory experiments have been conducted investigate field. This study investigated its by constructing a large-scale physical model according situ conditions panel. Theoretical analysis was used reveal mechanism distribution overburden. modelling results showed that: (1) major principal arch-shaped, strata overlying both solid zones gob...

Hydraulic flushing can increase the efficiency of gas extraction by artificially modifying coal reservoir. Considering plastic failure mass, an improved gas–liquid–solid coupling model for hydraulic and is constructed. The parameter evolution in process was numerically investigated to determine optimal borehole arrangement flushing. results show that relative permeability gradually increases with initial dewatering. rates both regular enhanced increasing–decreasing trend. An increased...

Abstract With the continuous increase of mining in depth, gas extraction faces challenges low permeability, great ground stress, high temperature and large pressure coal seam. The controllable shock wave (CSW), as a new method for enhancing permeability seam to improve extraction, features advantages efficiency, eco-friendly, cost. In order better utilize CSW into mine, mechanism feasibility enhanced need be studied. this paper, basic principles, experimental tests, mathematical models,...

To reveal the evolution law of coal skeleton deformation during process CO 2 flooding and displacing CH 4 in seam, a fluid-solid coupling mathematical model injection enhanced drainage was established based on Fick’s law, Darcy’s ideal gas state equation, Langmuir equation. Meanwhile, numerical simulations were carried out by implementing COMSOL Multiphysics. Results show that content both regular gradually decreases with time, decreasing rate is high between 10 60 days. Compared drainage,...

In order to explore the impact of scale effect on coal seepage from a microscopic perspective, CT scanning experiments were carried out samples selected Zhangcun Coal Mine in Shanxi Province. The scanned images processed by means Avizo software, and real pore fracture model was established through three-dimensional reconstruction technology. Based qualitative characterization pores fissures model, microstructure is analyzed. influence porosity permeability characteristics seam discussed...

Longitudinal tensile, longitudinal compressive, and flexural tests of bamboo from different regions were carried out, the values strength elastic modulus obtained. The probability distribution models mechanical properties in studied based on data. effects no waterproofing treatment, tung oil wood wax treatment property degradation response to 7 days soaking. main conclusions include: produced Yunnan Province highest, followed by Jiangxi Province, lowest Zhejiang Province. Weibull model...

Uniaxial tension experiments on precracked rocklike samples and the related numerical simulations using FRANC3D were performed to investigate growth mechanism of three-dimensional (3D) cracks in rocks under as well strength failure behavior samples. Experimental results indicate that geometric characteristics preexisting cracks, including crack dip angle, spacing, intensity, have significant effects modes Failure resulted from propagation a single coalescence multiple if spacing between...

In order to predict the coal outburst risk quickly and accurately, a PCA-FA-SVM based gas prediction model was designed. Principal component analysis (PCA) used pre-process original data samples, extract principal components of use firefly algorithm (FA) improve support vector machine model, compare analyze results with BP FA-SVM FA-BP SVM model. Accuracy rate, recall Macro-F1 time were as evaluation indexes. The show that: improves efficiency accuracy rate predicting is 0.962, 0.955, 0.957,...

Brittle failure is a fundamental pattern in many different materials, from small nanoscale materials with single crystals to the large earth crust. Many efforts have been dedicated understanding brittle mechanisms of individual and semi-brittle materials. Limited studies conducted on composite interaction energy feedback between Here we investigated coal-rock under uniaxial compression by laboratory tests numerical simulations. We used high-speed camera capture specimens. For all three...

Abstract The viscosity and density of different gases (CO 2 N ) vary with the gas species, composition temperature, which may raise variant results injection enhanced coalbed methane (ECBM) extraction. fluid–structure interaction within coal seam was established to study evolution strain in process ECBM extraction by injecting CO or . After verifying equations governing via experimental tests, simulated. characteristics induced sorption comprehensively analyzed. Results show that has strong...

The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick's law, Darcy's the ideal law and Langmuir equation, a damage-seepage-deformation coupling mathematical model CSW in combined with maximum tensile stress Mohr-Coulomb criterion established. This implemented into COMSOL Multiphysics simulate subsequent When isotropic in-situ are applied borehole wall, damage zone annular shape, increases sharply....