Simulation Evaluation of CO2-ECBM Potential in Karaganda Coal Basin in Kazakhstan

Karaganda Coal Basin is the largest coal basin in Kazakhstan with around one trillion cubic meters of coalbed methane, which has not been tapped to date. Also, simulation research on the production of coalbed methane from the Karaganda Coal Basin has not been conducted. Seeing that primary production of coalbed methane (CBM) is generally slow and recovery is not high, we proposed to evaluate the potential of implementing CO2-ECBM processes in Karaganda Coal Basin in Kazakhstan. It is known that CO2 adsorption on coal is much higher than methane so it is important to study the displacement mechanisms by CO2 injection. Using the geological parameters collected for Karaganda Coal Basin, main factors affecting methane production including different rates of CO2 injection and different starting times of CO2 injection were simulated and compared. CO2 injection into CBM reservoir is predicted to be effective due to competitive adsorption of these gases. This study provides a workflow model for evaluating and predicting efficient CBM production from the Karaganda Coal Basin. Results from simulation studies showed that injection of 110,000 m3/day of CO2 is as practical as injection of 150,000 m3/day, with small difference in recovery factor. The methane production enhances from 68.32% to 73.67-74.62% at injection pressure 15,000 kPa. The CO2 injection after 30% of primary recovery is the most efficient option. Early injection results in early breakthrough and high CO2 content in the producer well, while late injection leads to relatively low incremental recovery factor.