CO2 storage capacity of anthracite coal in deep burial depth conditions and its potential uncertainty analysis: a case study of the No. 3 coal seam in the Zhengzhuang Block in Qinshui Basin, China

Abstract

The storage of CO2 in deep unminable coal seams can mitigate greenhouse gas emissions. However, CO2 storage in deep anthracite coal is complex with some uncertainties in the estimation of CO2 storage capacity. Based on isothermal adsorption experiments and gas solubility experiments under high temperature and pressure conditions, the total storage capacity of CO2 in anthracite coal is discussed. The results show that the absolute adsorption amount is over 44 cm3/g at temperatures of 318.15, 335.65, and 353.15 K as well as adsorption equilibrium pressures of 10 MPa. The storage capacity of adsorbed and free gas is 35–70 cm3/g and 5–8 cm3/g, respectively, within a depth range of 1000–2000 m. The soluble gas can be ignored for its low content between 0.22 cm3/g and 0.28 cm3/g with a proportion of less than 1%. The storage capacity of CO2 may be estimated inaccurately because of the heterogeneity and uncertainty of the macroscopic geological conditions and coal reservoir parameters. Taking the No. 3 coal seam in Zhengzhuang block as an example, the storage priority area was divided into supercritical area and subcritical area with five sub-areas according to storage conditions, and the storage capacity was calculated, showing a relatively good storage potential.