144 / 2022-02-04 20:35:17

Effect of permeable and anisotropic coal reservoirs on CO2-ECBM

the staged inhibition, permeability, horizontal anisotropy, dominant seepage direction

（10）地下空间资源开发与利用 > 8. CO2地质封存

Gas driving water can cause staged inhibition on CH₄ production, and reservoir permeability has a critical influence on it. Taking the Shizhuangnan coalbed methane development block in Qinshui Basin as the research background, the impacts of permeability and horizontal anisotropy on CH₄ production and CO₂ sequestration are simulated numerically and then discussed adequately, and the displacement profile in the processes of gas driving water is analyzed. The results show that the reservoirs with low permeability or weak horizontal anisotropy are harmful to enhancing CBM recovery, but beneficial to CO₂ sinking. With the rise of permeability and anisotropy, the hysteresis time and staged inhibition time are observably shortened, and the staged inhibition level is markedly weakened, while the CH₄ output and CO₂ injection volume are significantly increased. However, high permeability and strong anisotropy easily tend to premature CO₂ breakthrough and the producers' shut-off, resulting in cumulative CH₄ production, CO₂ injection, and storage volume lower than expected. Upregulating the limit of CO₂ breakthrough concentration appropriately can effectively ameliorate the situation. Additionally, along the displacement direction, the displacement profile consists of sequential CO₂ enriched zone, CO₂-CH₄ enriched zone, CH₄ enriched zone, H₂O enriched zone. Ultimately, for field projects, the producers in the dominant seepage direction possess more potential of enhanced recovery in the short term, while those in the inferior seepage direction avoid becoming invalid only if a long-time injection measure is taken into the injectors.