Evolution law of coal seam permeability in CO2-ECBM process

Abstract

In order to study the spatio-temporal evolution law of coal seam permeability in the process of CO2-ECBM, a CO2-ECBM fluid-solid-thermal multi-field coupling numerical model is established by using COMSOL Multiphysics numerical simulation method based on the geological conditions of Liliu Mining Area as the engineering background. The CO2-ECBM process is numerically simulated by five-point well layout method, and the spatio-temporal evolution of coal permeability with CO2 injection is discussed. The results show that gas pressure, CO2 injection and shrinkage/expansion deformation of coal matrix are the key factors affecting permeability evolution. After the adsorption of CO2, the expansion deformation of coal matrix plays a leading role, occupying the pore space, resulting in the decrease of permeability, the mean permeability in the range affected by CO2 decreased by 40%. Along the CO2 injection well to the extraction well, the permeability is less and less affected by CO2, it shows a monotonic upward trend. The mean permeability increased by 14% outside the influence range of CO2.

Keywords

• coalbed methane
• gas extraction
• permeability
• co2-ecbm
• multi-physics field coupling