scholarly journals Numerical simulation investigations of coalbed methane drainage performance with multilateral well

2021 ◽  
Vol 11 (3) ◽  
pp. 1303-1321
Author(s):  
Songze Liu ◽  
Jianguang Wei ◽  
Yuanyuan Ma ◽  
Hongliang Liu ◽  
Xuemei Liu ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Length Distribution ◽  
Coupling Model ◽  
Extraction Process ◽  
Gas Extraction ◽  
Intersection Angle ◽  
Ratio Distribution ◽  
Mechanical Coupling ◽  
Cumulative Production ◽  
Positive Effect

AbstractA novel multilateral well for coalbed methane extraction was proposed in the study. There is a main wellbore at the longitudinal center of coal seam and four lateral wells at the horizontal center in the multilateral-well system. Compared with traditional drainage holes, multilateral-well system has a better performance on coalbed methane development. A hydraulic-mechanical coupling model of multilateral well was established, the pressure and permeability ratio distribution of the gas extraction process were analyzed comprehensively. The sensitivity analysis of lateral number, length distribution and intersection angle of multilateral-well system were studied. The results indicate that there is a minimum gas pressure distribution around the multilateral well and the overall permeability of coal seams increases with production time and the permeability around the multilateral well is larger than the area away from the multilateral well which induced by the gas desorb and matrix shrink. The quantity of lateral wells has a positive effect on cumulative production. When the total length of lateral wells is equal, the uniformity and symmetry of lateral length distribution are two key factors on the gas extraction performance. The minimum intersection angle has a positive effect on cumulative production. This study provides a better alternative for traditional drainage hole to obtain greater coalbed methane performance.

scholarly journals Rational Boreholes Arrangement of Gas Extraction from Unloaded Coal Seam

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Chaojun Fan ◽  
Sheng Li ◽  
Haohao Zhang ◽  
Zhenhua Yang
Keyword(s):  
Coal Seam ◽  
Coupling Model ◽  
Extraction Process ◽  
Gas Extraction ◽  
Coal Seams ◽  
Extraction Area ◽  
Mechanical Coupling ◽  
Blind Area ◽  
Blind Extraction ◽  
Seam Mining

In order to enhance gas extraction from unloaded coal seam by drilling borehole in the floor roadway, the mechanism of stress relief improving permeability by protective coal seam mining was analyzed. Based on the multiphysics field theory, the hydraulic-mechanical coupling model of gas extraction in the unloading coal seam was established, and the gas extraction process by drilling borehole in the floor roadway in the overburden of Panyi Coal Mine 1551 (1) panel was simulated. The influence of different drilling arrangements on the gas extraction effect was analyzed. The results show that the permeability of protected coal seams is characterized by zoning and can be divided into the permeability-enhanced zone, the permeability-reduced zone, and the original permeability zone according to the stress state of coal seam. Under the condition of uniform borehole distribution, the gas pressure decreased slowly in the permeability-reduced zone and is still greater than 0.74 MPa after 180 days of extraction, and there is a large extraction blind area in the protected panel. Under the condition of nonuniform borehole distribution arrangement according to the characteristics of permeability zoning, the effective extraction area can almost cover the protected panel, and the blind extraction area is reduced by 91.22% when compared to uniform borehole distribution. These can provide a reference for unloading gas extraction under similar conditions.

scholarly journals Simulation of the Extraction Efficiency of Coalbed Methane under Water Injection: A Gas-Liquid-Solid Coupling Model

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Hai Pu ◽  
Liqiang Zhang ◽  
Xu Dong ◽  
Tao Jing ◽  
Xu Junce
Keyword(s):  
Elastic Modulus ◽  
Coal Seam ◽  
Coalbed Methane ◽  
Extraction Efficiency ◽  
Water Injection ◽  
Free Water ◽  
Coupling Model ◽  
Experimental Results ◽  
Gas Extraction ◽  
Gas Drainage

Coalbed methane is always a major hidden danger that affects mining safety in coal mines. In the study of coal seam water injection to control gas disaster, the increase of free water content is helpful to destroy the integrity of coal seam and to promote the flow of gas in fractures. However, when the free water fills the fracture space, it will increase the flow resistance of gas, and then will reduce the gas extraction efficiency. At present, there is currently no mathematical model describing the effects of coal seam water injection that combines these two aspects on gas drainage. In this study, a series of experiments were conducted to study the differences in mechanical property changes under wetting conditions with different coal samples. The experimental results show that the elastic modulus and compressive strength decrease as an exponential function with increasing water pressure. Based on the experimental results, a gas-liquid-solid coupling model including effective stress change and gas desorption is established and used to predict a field gas extraction application. According to the results of the numerical model, In the plastic failure zone of coal seam, the permeability increases, the elastic modulus drops and gas migrates faster. In the water wetting zone, the free water occupies the fracture space, which blocks the gas migration channel. The overall effect of water injection on gas extraction depends on which impact plays a dominant role. The established gas drainage model is validated by field data and can reflect the pattern of borehole damage and gas drainage under water injection.

scholarly journals Hydraulic-Mechanical Coupling Model with Dual-Porosity Dual-Permeability for Anisotropy Coal Seams and Its Application in Mine Gas Extraction

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Bingjie Huo ◽  
Xuedong Jing ◽  
Aiping He ◽  
Chaojun Fan
Keyword(s):  
Coal Seam ◽  
Pressure Gradient ◽  
Coupling Model ◽  
Dual Porosity ◽  
Gas Extraction ◽  
Anisotropy Coefficient ◽  
Fracture Permeability ◽  
Coal Seams ◽  
Mechanical Coupling ◽  
Matrix Permeability

The parameters of pore-fracture structure and permeability have a controlling effect on the behaviors of gas adsorption/desorption and transportation in coal reservoir. A mathematic model for coal seams is of great significance to evaluate the mass migration within the coal fracture-matrix system. In this paper, the hydraulic-mechanical coupling model considering both dual-porosity dual-permeability and anisotropy characteristics is first established by using the methods of theoretical analysis, nuclear magnetic resonance (NMR) test, and numerical simulation. Then, this model is applied to simulate the gas migration characteristics of No. 3 coal seam in Changping Mine, China. Results show that the pore structure of No. 3 coal seam is characterized by small radius of pores and pore throats, which is determined by the NMR test, verifying the dual-permeability dual-porosity of coal seams. Both matrix permeability and fracture permeability increase approximately linearly with the process of mine gas extraction. The increased magnitude of the matrix permeability is greater than that of the fracture permeability. The permeability is inversely proportional to the anisotropy coefficient. The pressure gradient within the coal matrix and fracture increases first and then decreases with the extraction time. This pressure gradient is proportional to the anisotropy coefficient at the early stage of extraction and is inversely proportional to the anisotropy coefficient at the later stage. The seepage and diffusion flux are proportional to the anisotropy coefficient. The proportion of matrix-to-fracture seepage flux to the total flux increases first and then decreases to a certain value. The proposed model provides a guide for accurate designation of gas extraction from coal seams.

scholarly journals Coal Seam Gas Extraction by Integrated Drillings and Punchings from the Floor Roadway considering Hydraulic-Mechanical Coupling Effect

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-10
Author(s):  
Chaojun Fan ◽  
Haiou Wen ◽  
Sheng Li ◽  
Gang Bai ◽  
Lijun Zhou
Keyword(s):  
Coal Seam ◽  
Coal Mines ◽  
Coupling Model ◽  
Gas Pressure ◽  
Gas Content ◽  
Engineering Practice ◽  
Gas Extraction ◽  
Coal Seam Gas ◽  
Mechanical Coupling ◽  
Gas Disasters

Owing to the exhaustion of shallow coal resources, deep mining has been occupied in coal mines. Deep buried coal seams are featured by the great ground stress, high gas pressure, and low permeability, which boost the risk of gas disasters and thus dramatically threaten the security about coal mines. Coal seam gas pressure and gas content can be decreased by gas extraction, which is the primary measure to prevent and control mine gas disasters. The coal mass is simplified into a continuous medium with dual structure of pores and fractures and single permeability. In consideration of the combined effects of gas slippage and two-phase flow, a hydraulic-mechanical coupling model for gas migration in coals is proposed. This model involves the equations of gas sorption and diffusion, gas and water seepage, coal deformation, and evolution of porosity and permeability. Based on these, the procedure of gas extraction through the floor roadway combined with hydraulic punching and ordinary drainage holes was simulated, and the gas extraction results were used to evaluate the outburst danger of roadway excavation and to verify the engineering practice. Results show that gas extraction can reduce coal seam gas pressure and slow down the rate of gas release, and the established hydraulic-mechanical coupling model can accurately reveal the law of gas extraction by drilling and punching boreholes. After adopting the gas extraction technology of drilling and hydraulic punching from the floor roadway, the remaining gas pressure and gas content are reduced to lower than 0.5 MPa and 5.68 m3/t, respectively. The achievements set a theoretical foundation to the application of drilling and punching integrated technology to enhance gas extraction.

THE EFFECTS OF ELASTIC STIFFENING ON THE EVOLUTION OF THE STRESS FIELD WITHIN A SPHERICAL ELECTRODE PARTICLE OF LITHIUM-ION BATTERIES

2013 ◽  
Vol 05 (04) ◽  
pp. 1350040 ◽  
Author(s):  
WENBIN ZHOU ◽  
FENG HAO ◽  
DAINING FANG
Keyword(s):  
Stress Field ◽  
Lithium Ion Batteries ◽  
Internal Stress ◽  
Concentration Gradient ◽  
Concentration Field ◽  
Lithium Ion ◽  
Coupling Model ◽  
Ion Concentration ◽  
Hysteresis Phenomenon ◽  
Mechanical Coupling

Poor cyclic performance of lithium-ion batteries is calling for efforts to study its capacity attenuation mechanism. The internal stress field produced in the lithium-ion battery during its charging and discharging process is a major factor for its capacity attenuation, research on it appears especially important. We established an electrochemical –mechanical coupling model with the consideration of the influence of elastic stiffening on diffusion for graphite anode materials. The results show that the inner stress field strongly depends on the lithium-ion concentration field, greater concentration gradients lead to greater stresses. The evolution of the stress field is similar to that of the concentration gradient but lags behind it, which shows hysteresis phenomenon. Elastic stiffening can lower the concentration gradient and increase elastic modulus, which are two major factors influencing the inner stress field. We conclude that the latter is more dominant compared to the former, and elastic stiffening acts to increasing the internal stress.

scholarly journals A fully multifield coupling model of gas extraction and air leakage for in-seam borehole

2021 ◽  
Vol 7 ◽  
pp. 1293-1305
Author(s):  
Junxiang Zhang ◽  
Yanwei Liu ◽  
Peiliang Ren ◽  
Hongkai Han ◽  
Shuai Zhang
Keyword(s):  
Coupling Model ◽  
Gas Extraction ◽  
Air Leakage

Analysis of Transient Thermal Stress of IGBT Module Based on Electrical-Thermal-Mechanical Coupling Model

2014 ◽  
Vol 986-987 ◽  
pp. 823-827
Author(s):  
Qing Yuan Zheng ◽  
Min You Chen ◽  
Bing Gao ◽  
Nan Jiang
Keyword(s):  
Thermal Stress ◽  
Stress Distribution ◽  
Uniform Distribution ◽  
Inelastic Strain ◽  
Coupling Model ◽  
Power Module ◽  
Mechanical Coupling ◽  
Fem Method ◽  
Igbt Module ◽  
Solder Layer

Reliability of IGBT power module is one of the biggest concerns regarding wind power system, which generates the non-uniform distribution of temperature and thermal stress. The effects of non-uniform distribution will cause failure of IGBT module. Therefore, analysis of thermal mechanical stress distribution is crucially important for investigation of IGBT failure mechanism. This paper uses FEM method to establish an electrical-thermal mechanical coupling model of IGBT power module. Firstly, thermal stress distribution of solder layer is studied under power cycling. Then, the effects of initial failure of solder layer on the characteristic of IGBT module is investigated. Experimental results indicate that the strain energy density and inelastic strain are higher which will reduce reliability and lifetime of power modules.

Sign in / Sign up

Export Citation Format

Share Document