Supercritical-CO2 Adsorption Quantification and Modeling for a Deep Coalbed Methane Reservoir in the Southern Qinshui Basin, China

Huihu Liu; Shuxun Sang; Shimin Liu; Haiyan Wu; Tianhe Lan; Hongjie Xu; Bo Ren

doi:10.1021/acsomega.9b00599

Supercritical-CO₂ Adsorption Quantification and Modeling for a Deep Coalbed Methane Reservoir in the Southern Qinshui Basin, China

ACS Omega. 2019 Jul 5;4(7):11685-11700. doi: 10.1021/acsomega.9b00599. eCollection 2019 Jul 31.

Authors

Huihu Liu¹, Shuxun Sang², Shimin Liu³, Haiyan Wu¹, Tianhe Lan¹, Hongjie Xu¹, Bo Ren⁴

Affiliations

¹ School of Earth and Environment and School of Foreign Language, Anhui University of Science & Technology, Huainan 232001, China.
² School of Resource and Earth Science, China University of Mining and Technology, Xuzhou 221116, China.
³ Department of Energy and Mineral Engineering, G3 Center and Energy Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
⁴ State Key Laboratory of Deep Coal Mining & Environment Protection, Huainan Mining Industry (Group) Company Limited, Huainan 232001, China.

Abstract

Accurate depiction of the adsorption capacity of supercritical CO₂ (ScCO₂) by existing adsorption models is an important focus for deep coal seams in CO₂-enhanced coalbed methane (CO₂-ECBM) recovery. To investigate the applicability of different adsorption models for the adsorption isotherms of ScCO₂, the validities of 10 different adsorption models were analyzed, based on analyses of the adsorption characteristics of ScCO₂ from deep coal seams of the Southern Qinshui Basin, China. These models include the Langmuir (L) model, two-parameter Langmuir (TL) model, Toth (T) model, Langmuir-Freundlich (LF) model, extended Langmuir (EL) model, double parameter Brunauer-Emmett Teller model, three-parameter BET (TBET) model, Dubinin-Radushkevich (D-R) model, Dubinin-Astakhov (D-A) model, and Ono-Kondo lattice (OK) model. These models were tested for both the excess and absolute adsorption capacities of ScCO₂ under various temperatures and pressures. The simulation accuracy of the different adsorption models was analyzed. The optimal models for the adsorption of ScCO₂ in deep coal seams were selected based on a comprehensive analysis of the simulation parameters, standard error, and residual sum of squares. There were obvious differences in the validity of the different adsorption models in terms of the excess adsorption capacity and absolute adsorption capacity of ScCO₂. The D-A and D-R models are the optimal adsorption models for the adsorption isotherms of the excess adsorption of ScCO₂ for the whole tested pressure range. The T, TL, and D-R models are the optimal adsorption models in simulation of the excess adsorption capacity of ScCO₂ for the selected adsorption models when the equilibrium pressure is divided into two sections at the point of 8.13 MPa. In simulation of the absolute adsorption capacity of ScCO₂, the TBET and LF models are the optimal adsorption models among the selected models when the equilibrium pressure is less than or equal to 8.13 MPa. The linear, exponential, logarithmic, power function, and polynomial adsorption simulation all have good precision in the simulation of the absolute adsorption capacity of ScCO₂ when the pressure is beyond 8.13 MPa.