Quantitative Analysis of the Effect of CO2 Adsorption on the Permeable Characteristics of Coal Under True Triaxial Stress Conditions

Abstract

ABSTRACT As a heterogeneous porous medium, the anisotropy of the coal body increases the difficulty of retesting and studying the mechanism of internal gas migration. Therefore, in this paper, we analyzed the mechanism of carbon dioxide adsorption properties in the evolution of coal body deformation and permeability. The results of this study are as follows: (1) The adsorption pressure of the coal body was divided into slow increase zone, stable increase zone, and rapid increase zone. (2) With the increasing pressure of the gas, there are two distinct turning points in the changing trend of coal permeability, which is divided into the slow increase zone and the rapid increase zone. (3) the effect of gas adsorption on the permeability of coal consisted of sensitive and insensitive areas. When the gas pressure was less than 1MPa, the impact of gas adsorption on the coal sample permeability was insignificant, while the effect was significant when the gas pressure was in the range of 1-2 MPa. INTRODUCTION Carbon dioxide (CO2) and methane (CH4) are the main components of greenhouse gases, which are mainly derived from the burning of non-coal fuels and exhaust from coal mines, respectively. The rapid increases in these two types of gases will trigger global warming issues. Implementation of CO2 capture and sequestration technology (CO2 capture and sequestration, CCS) can reduce CO2 emissions from the energy industry by 20% (Haszeldine, 2010; Oschatz & Antonietti, 2017). CO2 can be sealed in depleted oil and gas layers, and uneconomical coal seams(Konstantinovskaya et al., 2014; Rutqvist et al., 2008; Yamamoto et al., 2013). In particular, when sealed in coal seams, CBM can be replaced. Therefore, the intensive extraction of coal seam gas (CH4) and the realization of CO2 sequestration technology (CO2 sequestration in coals with enhanced coal-bed methane recovery, CO2-ECBM) have attracted extensive research attention from researchers in China and abroad (Li et al., 2011; P. Liu et al., 2019; Onoja et al., 2019; Raziperchikolaee & Mishra, 2019; Vilarrasa et al., 2010)