Numerical simulation of CO2 geological sequestration and CO2-ECBM in coal beds of Longtan Formation, Xiangzhong Depression, Hunan Province, China

Abstract

Geological sequestration of carbon dioxide (CO₂) is an effective method to reduce greenhouse gases and an important technology for carbon neutralization. Among all geological sequestration sites, coal reservoirs are potentially effective and practicable. The Xiangzhong Depression of Hunan Province of China is selected as the research area, and the coal seam of Longtan Formation is the target reservoir in this paper. CO₂-enhanced coalbed methane (CO₂-ECBM) and CO₂ sequestration capacity are both simulated according to the laboratory experiments on reservoir parameters. During simulation, four production wells and one injection well were designed, and the simulation process can be divided into two stages: CO₂-ECBM and CO₂ geological storage. The CO₂-ECBM stage refers to CO₂ injection for increasing methane production, and the CO₂ geological storage stage aims to predict the CO₂ sequestration capacity. After that, sensitivity analyses of sequestration effect are carried out. During the simulation, when maintaining a constant pressure injection of CO₂ under the original conditions of 0.01 mD permeability, 9% porosity, and 1.47 MPa reservoir methane pressure, the total storage amount is only 0.14 × 10⁶ m³. However, the storage amount increases significantly to 6.62 × 10⁶ m³ if the permeability increases to 1.5 mD. Orthogonal simulation indicates that permeability has the greatest impact on CO₂ sequestration. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.