Articles | Volume 372
Proc. IAHS, 372, 455–462, 2015
https://doi.org/10.5194/piahs-372-455-2015
Proc. IAHS, 372, 455–462, 2015
https://doi.org/10.5194/piahs-372-455-2015

  12 Nov 2015

12 Nov 2015

Numerical and experimental study of strata behavior and land subsidence in an underground coal gasification project

N. N. Sirdesai1, R. Singh1, T. N. Singh1, and P. G. Ranjith2 N. N. Sirdesai et al.
  • 1Department of Earth Sciences, Indian Institute of Technology Bombay, Mumbai, India
  • 2Deep Earth Energy Lab, Monash University, Clayton, VIC, 3800, Australia

Abstract. Underground Coal Gasification, with enhanced knowledge of hydrogeological, geomechanical and environmental aspects, can be an alternative technique to exploit the existing unmineable reserves of coal. During the gasification process, petro-physical and geomechanical properties undergo a drastic change due to heating to elevated temperatures. These changes, caused due to the thermal anisotropy of various minerals, result in the generation of thermal stresses; thereby developing new fracture pattern. These fractures cause the overhead rock strata to cave and fill the gasification chamber thereby causing subsidence. The degree of subsidence, change in fluid transport and geomechanical properties of the rock strata, in and around the subsidence zone, can affect the groundwater flow. This study aims to predict the thermo-geomechanical response of the strata during UCG. Petro-physical and geomechanical properties are incorporated in the numerical modelling software COMSOL Multiphysics and an analytical strength model is developed to validate and further study the mechanical response and heat conduction of the host rock around the gasification chamber. Once the problems are investigated and solved, the enhanced efficiency and the economic exploitation of gasification process would help meet country's energy demand.

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Short summary
Petro-physical and geomechanical properties undergo a drastic change due to heat generated during underground coal gasification. The thermal anisotropy of the minerals result in the generation of thermal stresses which result in fracturing of the rock. The new fractures lead to the failure of overhead strata thereby causing subsidence. This paper aims to predict the thermo-geomechanical response of the strata during UCG using COMSOL Multiphysics.