Enhancing Recovery of Low-Productivity Coalbed Methane Wells in Medium-Shallow Reservoirs by CO2 Huff-and-Puff

Coalbed methane (CBM) is a vital clean energy resource, yet its extraction efficiency is often hindered by rapid production decline and low production rates in medium-shallow reservoirs. This study investigates the potential of CO2 huff-and-puff technology to enhance CBM recovery and achieve CO2 storage in low-productivity wells. A comprehensive model, constructed based on the geological conditions of the Qinshui Basin, was developed. Numerical simulations revealed that CO2 huff-and-puff significantly improves CH4 production by displacing adsorbed CH4 and maintaining reservoir pressure. Key findings indicate that higher CO2 injection volumes yield substantial increases in both peak CH4 production and cumulative production compared with conventional extraction. Optimal soaking times balance recovery efficiency and operational costs. Sensitivity analysis identified gas diffusion coefficients, initial permeability, and Langmuir volume constants as critical geological parameters influencing the performance. This study preliminarily demonstrates the feasibility of large-scale CO2 huff-and-puff for enhancing production in low-productivity CBM wells and provides theoretical insights for revitalizing China’s underperforming CBM wells while advancing carbon neutrality goals, although further experimental validation is still required.