Оценка на основе моделирования одновременных потенциалов накопления CH4 во время CO2-ECBM в Карагандинском угольном бассейне

Karaganda Basin contains the largest coalbed methane (CBM) reserve in Kazakhstan. We previously modelled the enhanced coalbed methane (ECBM) process by injecting CO₂ into a typical well group which showed high production potential. With the global agreement on carbon neutrality, it is advantageous to explore the CO₂ storage potential during CO₂-ECBM in Karaganda Coal Basin. The CO₂ storage potential of a given coal seam volume in the Karaganda Coal Basin is evaluated by setting up an extended 5-well pattern in a compositional reservoir simulator. The CO₂-ECBM process is simulated by incorporating the reservoir parameters reported for the Karaganda Coal Basin, with variable CO₂ injection rate and well pressures to optimize the injection strategy, such as the necessity of well stimulation. Simulation results showed that primary depletion followed by CO₂ injection is a promising win-win strategy. Based on parameter sensitivity analysis, the CO₂ injection rate should have an optimal value under pressure constraint, since higher injection rate does not contribute remarkably to the recovery. With the aid of CO₂ injection, the methane recovery could be enhanced from 35.1×10⁶ kg to 40.2×10⁶ kg by 14.5% during the 4-year CO₂ injection at constant rate of 60,000 m³/day with constraint pressure of 15,000 psi. Correspondingly over 99.98% of injected CO₂ can be concurrently stored in the form of adsorbed and free gas in these case scenarios. Simulation results suggest that commercial CBM production could be established in the Karaganda Coal Basin, if properly implemented; meanwhile, the process entails enormous potential for CO₂storage and represents a new opportunity for the Karaganda coal industry.