Abstract
Tectonic coals in coal seams may affect the process of enhanced coalbed methane recovery with CO2 sequestration (CO2-ECBM). The main objective of this study was to investigate the differences between supercritical CO2 (ScCO2) and intact and tectonic coals to determine how the ScCO2 changes the coal’s properties. More specifically, the changes in the tectonic coal’s pore structures and its gas desorption behavior were of particular interest. In this work, mercury intrusion porosimetry, N2 (77 K) adsorption, and methane desorption experiments were used to identify the difference in pore structures and gas desorption properties between and intact and tectonic coals after ScCO2 treatment. The experimental results indicate that the total pore volume, specific surface area, and pore connectivity of tectonic coal increased more than intact coal after ScCO2 treatment, indicating that ScCO2 had the greatest influence on the pore structure of the tectonic coal. Additionally, ScCO2 treatment enhanced the diffusivity of tectonic coal more than that of intact coal. This verified the pore structure experimental results. A simplified illustration of the methane migration before and after ScCO2 treatment was proposed to analyze the influence of ScCO2 on the tectonic coal reservoir’s CBM. Hence, the results of this study may provide new insights into CO2-ECBM in tectonic coal reservoirs.
Highlights
As a major greenhouse gas, CO2 causes global warming and initiated a series of negative effects on the balance of the natural ecosystem and the sustainable development of human society [1,2,3,4,5,6,7].To mitigate CO2 emissions into the atmosphere, enhanced coalbed methane recovery with CO2 sequestration (CO2 -ECBM) is considered to be a promising technology, and it receives widespread attention [8,9,10,11,12]
Both the intact coal and tectonic coal samples used in the experiments were collected from the Shanxi Formation #3 coal seam in the Sihe coal mine
The southern Qinshui basin is a major CBM production area, and the area in which China first carried out a pilot CO2 -ECBM project [33]
Summary
To mitigate CO2 emissions into the atmosphere, enhanced coalbed methane recovery with CO2 sequestration (CO2 -ECBM) is considered to be a promising technology, and it receives widespread attention [8,9,10,11,12]. This technology can provide CO2 storage, but can enhance the production of coalbed methane (CBM). Fulton et al observed that the recovery of CH4 after CO2 injection was 57% higher than that of natural emissions [13]. In 1996, the San Juan Basin was selected as Energies 2018, 11, 3419; doi:10.3390/en11123419 www.mdpi.com/journal/energies
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