Research on CO2-enhanced coalbed methane extraction effect based on different reservoir parameters and injection timing
LI Ao
SHI Tielian
SU Chuanyun
HE Xueming
BI Sicun
LIN Zhizhong
SONG Liuni
GUO Xiaoyang
Abstract：The CO2 injection enhanced coalbed methane extraction technology(CO2-ECBM)can not only significantly improve the efficiency of coalbed methane extraction,but also reduce greenhouse gas emissions,which is crucial for alleviating the global en-ergy crisis and the greenhouse effect.To realistically restore the CH4 recovery situation in coal seams,a thermal-hydro-mechanical coupling model was constructed,considering coal deformation,gas-water transport,and thermal expansion.Utilizing numerical sim-ulation,the coalbed methane production performance of conventional extraction and CO2-enhanced extraction was compared and studied.The impacts of injection temperature,injection pressure,and initial water saturation on CO2-ECBM engineering were analy-zed,and the optimal starting time for CO2 injection was determined.The results show that the enhancement factor of 3#coal seam in Qinshui Basin is 1.37 after 4000 days of extraction,which indicates the feasibility of CO2-enhanced coalbed methane recovery;due to the competitive effects of pore pressure,gas adsorption/desorption and thermoelastic expansion strain,the permeability shows a decreasing-increasing-decreasing trend;increasing the injection temperature and pressure will raise the temperature of the coal rese-rvoir,promote the production of CH4 and the storage of CO2,and increase the decline in permeability;the greater the initial water sat-uration,the less favorable it is for gas production and storage,and the smaller the decline in permeability;Delaying the injection time helps to increase the recovery rate of CH4 and the well closure threshold,but it will have a negative impact on the average produc-tion rate of CH4;when the start time of CO2 injection was 2 500 days,the average output rate was 1 142.10 m3/d,and the economic benefits of this demonstration project reached the optimum.The research results have enriched the stimulation mechanism of CO2-ECBM under different reservoir parameters and provided a new theoretical perspective for the optimization of its injection timing.
Keywords：CO2-enhanced coalbed methane extractiongas-water transportreservoir parametersoptimal injection timingnumer-ical simulation
Publication Date：2025-08-20
Online Publishing Date：2025-08-18(First online date of this platform, not the publication date of the document)
Pages：13( 1-13 )