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Application of the thermoporoelasticity model in numerical modelling of underground coal gasification influence on the surrounding medium

Studia Geotechnica et Mechanica
Volume 43 (2021): Issue 2 (June 2021)
By:
Open Access
|Jun 2021

Figures & Tables

Figure 1

Schematic of the UCG process (linked vertical wells method), with water entering from the surrounding rocks [6].
Schematic of the UCG process (linked vertical wells method), with water entering from the surrounding rocks [6].

Figure 2

Generated finite element mesh determining the model's geometry (non-uniform scale, aspect ratio 5:1). Geological layers: 1. sandstone, 2. clayey pebble, 3. clay, 4. lignite (UCG generator is located in the middle of this layer), 5. clay, 6. clayey sand, 7. clay, 8. silty clay.
Generated finite element mesh determining the model's geometry (non-uniform scale, aspect ratio 5:1). Geological layers: 1. sandstone, 2. clayey pebble, 3. clay, 4. lignite (UCG generator is located in the middle of this layer), 5. clay, 6. clayey sand, 7. clay, 8. silty clay.

Figure 3

Cross-section (y = 750 m) through the area of interest – position of coal gasification generator marked at the centre.
Cross-section (y = 750 m) through the area of interest – position of coal gasification generator marked at the centre.

Figure 4

Main boundary conditions on cross-section, (non-uniform scale, aspect ratio5:1). Geological layers: 1. sandstone, 2. clayey pebble, 3. clay, 4. lignite (UCG generator is located in this layer), 5. clay, 6. clayey sand, 7. clay, 8. silty clay.
Main boundary conditions on cross-section, (non-uniform scale, aspect ratio5:1). Geological layers: 1. sandstone, 2. clayey pebble, 3. clay, 4. lignite (UCG generator is located in this layer), 5. clay, 6. clayey sand, 7. clay, 8. silty clay.

Figure 5

Evolution of temperature at selected points of the gasified area.
Evolution of temperature at selected points of the gasified area.

Figure 6

Evolution of temperature changes around the coal gasification generator over time: a) start, b) 0.5 year, c) 1 year, d) 1.5 year, e) 2 year, f) 2.5 year.
Evolution of temperature changes around the coal gasification generator over time: a) start, b) 0.5 year, c) 1 year, d) 1.5 year, e) 2 year, f) 2.5 year.

Figure 7

Water vapour presence in cross-section at times a) start, b) 0.5 year, c) 1 year, d) 1.5 year, e) 2 years f) 2.5 year.
Water vapour presence in cross-section at times a) start, b) 0.5 year, c) 1 year, d) 1.5 year, e) 2 years f) 2.5 year.

Figure 8

Spatial situation of area of water vapour presence at time t = 1 year.
Spatial situation of area of water vapour presence at time t = 1 year.

Figure 9

Distribution of displacements (m) in the cross-section at y = 750 m at times a) 1 month, b) 0.5 year, c) 1 year, d)2 years.
Distribution of displacements (m) in the cross-section at y = 750 m at times a) 1 month, b) 0.5 year, c) 1 year, d)2 years.

Figure 10

a) Charts of displacements (m) over time, b) 3D vector field of displacements near the generator at t = start, c) displacement vector field near the generator at time t = 2 years.
a) Charts of displacements (m) over time, b) 3D vector field of displacements near the generator at t = start, c) displacement vector field near the generator at time t = 2 years.

Figure 11

Vector field of horizontal displacements (m): a–d) on the background of the temperature in cross-section z = 51.5: a) 1 month, b) 1 year c) 2 year, d) 3 year e) horizontal displacements over time (A and B).
Vector field of horizontal displacements (m): a–d) on the background of the temperature in cross-section z = 51.5: a) 1 month, b) 1 year c) 2 year, d) 3 year e) horizontal displacements over time (A and B).

Figure 13

Vector field of water conduction rate (m/s) on the background of the permeability (m/s) in cross-section y = 750 m at t = 1.5 year.
Vector field of water conduction rate (m/s) on the background of the permeability (m/s) in cross-section y = 750 m at t = 1.5 year.

Figure 14

Heat transfer coefficient (W/m/K) at t = 1 year: cross-section y = 750 m, close-up of gasification area.
Heat transfer coefficient (W/m/K) at t = 1 year: cross-section y = 750 m, close-up of gasification area.

Figure 15

A) temperature (°C) after 6 years when thermal parameters of water vapour were accepted in volume, where phase transition occurred, b) temperature in case, where no phase transition in the pores was modelled c) time course of temperature in both cases at point x = 71,5 m, y = 75,0 m, z = 63 m.
A) temperature (°C) after 6 years when thermal parameters of water vapour were accepted in volume, where phase transition occurred, b) temperature in case, where no phase transition in the pores was modelled c) time course of temperature in both cases at point x = 71,5 m, y = 75,0 m, z = 63 m.

Material parameter values of individual geological layers_

LayerRoof min [m]Roof max [m]f [−]N [Pa]A [Pa]α [−]ρs [Mg/m3]K [m/s]cv [J/kg/K]λ [W/m/K]
Sandstone4.710.90.152.31E+093.46E+091.16E-052.65.00E-0711003.1
Clayey pebble25.232.70.283.90E+062.40E+076.00E-062.533.00E-066392.5
Clay50500.311.32E+076.91E+075.80E-062.383.00E-085662.1
Coal*53530.25.80E+088.70E+085.00E-061.215.00E-0912500.5
Clay57.269.80.41.28E+069.42E+065.90E-062.626.00E-084812.9
Clayey sand80.5950.321.30E+069.00E+066.00E-062.491.20E-068893.5
Clay125.9149.90.372.50E+061.85E+076.10E-062.717.00E-085141.4
Silty clay166.11840.283.30E+061.50E+076.00E-062.665.00E-086121.9

Thermal parameters of individual pore fluids and medium_

Thermal expansion coefficient 1) [1/K]Initial heat transfer coefficient [W/m/K]specific heat [J/kg/K]
Water69·10−60.64150
Water vapour1/T16.2·10−31970
Medium-λ = (1 − f) λs + fλfcν = (ρ1 cνs + ρ2 cνf) / ρ
DOI: https://doi.org/10.2478/sgem-2021-0004 | Journal eISSN: 2083-831X | Journal ISSN: 0137-6365
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Language: English
Page range: 116 - 134
Submitted on: Aug 26, 2020
Accepted on: Feb 14, 2021
Published on: Jun 30, 2021
Published by: Wroclaw University of Science and Technology
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
poroelasticity,
thermoporoelasticity,
compressible pore fluid,
THM,
thermo-hydro-mechanical modelling,
UCG,
underground coal gasification
Related subjects:
Geosciences,
Geosciences, other,
Materials sciences,
Composites,
Porous materials,
Physics,
Mechanics and fluid dynamics

© 2021 Anna Uciechowska-Grakowicz, Tomasz Strzelecki, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution 4.0 License.

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