Subsidence Associated With Single and Multicavities for Underground Coal Gasification

1982 ◽  
Vol 104 (2) ◽  
pp. 99-104 ◽  
Author(s):  
J. M. Avasthi ◽  
G. J. Harloff
Keyword(s):  
Coal Gasification ◽  
Three Dimensional ◽  
Ground Level ◽  
Theoretical Development ◽  
Underground Coal Gasification ◽  
Elastic Parameters ◽  
Empirical Correction ◽  
Empirical Correction Factor ◽  
Incomplete Closure ◽  
Cavity Width

The three-dimensional theoretical development of Berry and Sales [1] has been extended to bring the subsidence predictions into agreement with the British National Coal Board comprehensive set of empirical data. New elastic parameters have been determined to fit the amplitude of the ground level subsidence. An empirical correction factor was developed to account for small cavity width-to-depth ratio cases. This correction is believed to account for incomplete closure for half width-to-depth ratios below 0.3. The theory has also been modified to bring the subsidence profiles into agreement with the foregoing referenced data. The development has been used to predict subsidence for an actual U.S. coal mining case with multiple cavities. The theory was also used to predict subsidence level and profile for a recent Gulf/DOE UCG test conducted in a steeply dipping coal seam near Rawlins, Wyoming.

A Side Wall Burn Model for Cavity Growth in Underground Coal Gasification

1983 ◽  
Vol 105 (2) ◽  
pp. 145-155 ◽  
Author(s):  
T. L. Eddy ◽  
S. H. Schwartz
Keyword(s):  
Coal Gasification ◽  
Cavity Growth ◽  
Side Wall ◽  
Field Tests ◽  
Underground Coal Gasification ◽  
Convection Diffusion ◽  
Bituminous Coals ◽  
Thin Seam ◽  
Burn Through ◽  
Cavity Width

A mechanistic computer model is presented which predicts the 3-D cavity growth during the gasification phase of underground coal gasification. Developed for swelling bituminous coals, the model also obtains reasonable cavity width and length values for shrinking sub-bituminous coals. The model predicts cavity shape and burn-through times based on the coal properties, seam thickness, water reacting and the interwell distance. Employing a 2-D boundary layer model to determine the convective diffusion rate of oxygen to the reacting walls, it is found that natural convection diffusion must be included. The model includes flow in the injection region, the swirling, mixing effect in the cavity, and transitions from thick to thin seam geometry. Simulations of the Hanna II, Phase 2 and Pricetown I field tests, as well as a parametric study on Pittsburgh seam coal, are presented.

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

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Anna Uciechowska-Grakowicz ◽  
Tomasz Strzelecki
Keyword(s):  
Mathematical Model ◽  
Coal Gasification ◽  
Surrounding Medium ◽  
Three Dimensional ◽  
Underground Coal Gasification ◽  
Temperature Dependent ◽  
Gas Laws ◽  
Specific Geometry ◽  
Pore Fluid Density ◽  
The Mathematical Model

Abstract The purpose of this paper was to present the thermoporoelasticity model adapted for application in modelling processes, where phase transition may occur, such as during underground coal gasification (UCG). The mathematical model of the medium (soil/rock with pores filled with liquid/gas) in non-isothermal conditions is based on Biot's poroelasticity model. The poroelasticity model is expanded here by the influence of temperature and adjusted to the case where both liquid and highly compressible fluid are present in pores by using the gas laws. This requires considering temperature-dependent physical quantities such as pore fluid density, heat transfer coefficient and viscosity as functions of temperature. Based on the proposed mathematical model and the finite element method, a numerical model was built for the purpose of computing processes occurring in the vicinity of the UCG generator. The result of the authors’ work is a three-dimensional (3D) model, which was not only modified, but derived straight from the laws of thermodynamics, where fields of displacement, temperature and fluid flow are coupled. The model makes it possible to determine results significant to modelling of the UCG process, the reach of the gaseous phase's presence in pores, subsidence values, temperature distribution and directions and rate of seepage, without losing the simplicity and elegance of Biot's original concept. Next, the results of simulations for a hypothetical deposit to estimate the environmental impact of UCG are presented. After applying specific geometry and parameters, the model can be useful for verifying if the chosen technology of UCG in specific conditions will be safe for the environment and infrastructure.

Cold Flow Simulation in Underground Coal Gasification (UCG) Cavities

2014 ◽  
Vol 1 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Dipankar Chatterjee ◽  
◽  
Satish Gupta ◽  
Chebolu Aravind ◽  
Rakesh Roshan
Keyword(s):  
Coal Gasification ◽  
Flow Simulation ◽  
Underground Coal Gasification ◽  
Cold Flow
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