Analogically Physical Simulation of Coalbed–Caprock Deformation in Geological Storage of CO2

CO2-enhanced coalbed methane (CO2-ECBM) can not only reduce greenhouse gas by geological storage of CO2 remarkablely, but also increase the recovery efficiency of Clean Coalbed gas. Therefore, it is regarded as a hot global topic, and is a significant approach to realizing the strategy of environment and energy of China. To better utilize coalbeds as the storage space, and to avoid the leakage of CO2 from the sealing site, coalbed and caprock in the pore-pressure limitation must be learnt, infiltrating ability and deforming modulus, etc. Because of the difficulty of underground exploration and inaccuracy of physical simulation, the numerical analysis so far is the main research technique. This paper employed sealing rods as the experimental materials according to their water swelling property, and built the swelling analogy relationship between water-injecting rod and gas-injecting coal. Furthermore, a similarly physical simulation was designed to measure the deformation and stress of coalbed–caprock system so as to provide the testing data for CO2-ECBM engineering. The results show that, based on the quantities analogy of water-swelling materials, all the data measured for the similar coalbed–caprock system are reasonable. In the caprock, a farther location from the injection well contributes a smaller deformation, and the deformation is the negative exponential function of the distance. In our experiment, coalbed strain can reach 10−4 in order of magnitudes, and therefore in the process of gas injection, the magnitude of stress change in the caprock can reach MPa. Finally, gradually upgrading the injecting pressure is a rational technology in the CO2-ECBM engineering. © 2018, Springer Nature Switzerland AG.