Thermo-hydro-mechanical coupled mathematical model for controlling the pre-mining coal seam gas extraction with slotted boreholes

Xue, Yi; Gao, Feng; Gao, Yanan; Liang, Xin; Zhang, Zhizhen; Xing, Yan

doi:10.1016/j.ijmst.2017.03.012

Cited by 40 publications

(28 citation statements)

References 17 publications

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“…Putting equation (13) into (6), the fully coupled governing equation for the gas flow affected by the coal seam deformation can be obtained: Therefore, Equations (3), (10), (13), and (14) define the fully coupled model of coal seam deformation and gas flow. The coupling relationships between the coal seam deformation and gas flow are shown in Figure 1.…”

Section: Coupled Governing Equationsmentioning

confidence: 99%

“…So, hydraulic fracturing and horizontal well are the key approaches to improve the reservoir seepage ability which increases the complexity of gas seepage in reservoir and greatly increases the difficulty of research . In previous studies, many scholars have made a lot of researches on the effect of stress and adsorption on seepage capacity of coal seam . However, there are relatively few studies on dynamic coupling and productivity of fractured horizontal well development in coal seam.…”

Section: Introductionmentioning

confidence: 99%

“…7,8 In previous studies, many scholars have made a lot of researches on the effect of stress and adsorption on seepage capacity of coal seam. [9][10][11][12][13] However, there are relatively few studies on dynamic coupling and productivity of fractured horizontal well development in coal seam. Therefore, to study the coupled model of coal seam deformation and gas flow in fractured horizontal well is very important to the seepage mechanism, influencing factors and productivity analysis of CBM development.…”

mentioning

confidence: 99%

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Numerical simulation of a coupled gas flow and geomechanics process in fractured coalbed methane reservoirs

Zhang

Chen³

et al. 2019

Energy Science & Engineering

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The pores and throats of coal seam are narrow, and the permeability is very low. It is a porous medium with complicated deformation mechanism. In the process of gas production, the change of stress, pore pressure, gas adsorption and desorption will lead to the change of grains, pore volume, and the seepage capacity of coal seam. Based on the theory of poroelastic and seepage mechanics, a physical model of fractured horizontal well and a coupled mathematic model of coal deformation and gas flow are established. The dynamic change model of permeability is deduced too. The development characteristics and laws of coalbed methane are numerically simulated by using numerical analysis software Comsol Multiphysics. Finally, the sensitivity of the key parameters in the model and the influence of the fracture parameters are analyzed. The results show that the application of fractured horizontal well is an effective measure to increase production of coalbed reservoirs; with the increase of Langmuir volumetric strain constant, fracture half‐length, and the numbers of fracture, the production of coalbed methane is increasing. In the case of constant total fracture length, number, and spacing, when fracture half‐lengths are long and short interlaced distribution, the production is the highest and it is the best fracture distribution pattern. The study provides a theoretical basis for the further study of coalbed deformation, gas migration, efficient, and rational development of coalbed methane reservoirs.

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Section: Coupled Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Numerical simulation of a coupled gas flow and geomechanics process in fractured coalbed methane reservoirs

Zhang

Chen³

et al. 2019

Energy Science & Engineering

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“…At present, gas predrainage along coal seam boreholes is mainly used in China, which is also an effective method for coal seam gas recovery and gas disaster prevention and control in coal mines, as shown in Figure . The effective extraction radius of borehole is an important parameter for this method, which is used for the determination of borehole spacing in gas extraction . If the gas extraction borehole spacing is too large, there will be extraction blind zones formed between extraction boreholes, bringing extremely large potential accidents to production in coal mines.…”

Section: Introductionmentioning

confidence: 99%

“…The effective extraction radius of borehole is an important parameter for this method, which is used for the determination of borehole spacing in gas extraction. 23,24 If the gas extraction borehole spacing is too large, there will be extraction blind zones formed between extraction boreholes, bringing extremely large potential accidents to production in coal mines. If the gas extraction borehole spacing is too small, the gas extraction rate and gas extraction volume may be increased to a certain extent, but this will increase the borehole construction workload, resulting in an increase in the gas extraction cost.…”

mentioning

confidence: 99%

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Wang

Chang

et al. 2019

Energy Science & Engineering

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The effective extraction radius of borehole is the main parameter for determining the design and layout for coalbed methane extraction. This paper is aimed at the problem that the criteria and calculation methods for the effective extraction radius of coal seams are not comprehensive. With Wudong Coal Mine in China taken as an example, the critical gas pressure (0.441 MPa) for the calculation of effective extraction radius is first defined. Next, the gas seepage unit model around the borehole is developed, and the theoretical mathematical expression to calculate the effective extraction radius is derived. Then, the numerical simulation of gas extraction is carried out through a computational fluid dynamics program, and the effective extraction radius is obtained numerically. Furthermore, the influence of original gas pressure, borehole diameter, and negative pressure of gas extraction on gas extraction is analyzed. Finally, the results from the theoretical calculation and numerical simulation are validated by the field engineering measurement and the average relative error is small (less than 10%). The results indicate that the effective extraction radius has a linear relationship with the extraction time. Moreover, it is found that the original gas pressure is the main factor affecting the effective extraction radius and the effective extraction radius is proportional to the borehole diameter and negative pressure through analysis. Therefore, the above findings can provide a theoretical basis for determining parameters such as borehole spacing and extraction time of gas extraction in coal mines.

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Evolution of Internal Swelling Coefficient Under Different Geometric Conditions and Its Influence on Gas Drainage

2022

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Thermo-hydro-mechanical coupled mathematical model for controlling the pre-mining coal seam gas extraction with slotted boreholes

Cited by 40 publications

References 17 publications

Numerical simulation of a coupled gas flow and geomechanics process in fractured coalbed methane reservoirs

Numerical simulation of a coupled gas flow and geomechanics process in fractured coalbed methane reservoirs

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Evolution of Internal Swelling Coefficient Under Different Geometric Conditions and Its Influence on Gas Drainage

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