Investigation on Mechanical Behaviour of Coal and Overburden Rock for UCG

Abstract

In recent years, the coupled UCG-CCS process has been considered as another potential CCS option, which can offer integrated energy recovery from coal and storage of CO2. However, existing potential problems may counteract its potential benefits. To develop a generic UCG-CCS site characterisation workflow, different aspects of this complex process, such as cavity progression and geomechanics, contamination of groundwater and subsidence impacts, need to be re-considered and understood. In this process, the thermo-mechanical behaviour of the roof rock and coal are the initial parameters to predict the stability and the development of the production cavity. These parameters affect heat conduction and the stability and caving of roof materials, especially under conditions of high stress and temperature. In this study, several experimental setups have been designed and built to study the thermo-mechanical properties of coal and overburden rock for UCG process. These experimental data can get an idea of elastic constants of rocks, the fracture growth mechanisms, the fracture orientations the maximum/yield stresses that the sample withstands, the conditions under which spalling occurs in overburden rock, as well as the rate which this take place. These results will be used as input for the modelling of the cavity growth of UCG.