CO2的地质埋存与资源化利用进展

把CO2注入油气藏、煤层提高油气采收率的方法(CO2-EOR、CO2-EGR、CO2-ECBM),因其在提高石油、天然气和煤层气采收率的同时,又能使一部分CO2永久地埋存于地下,实现油气增产和CO2减排的双赢效果,而成为当今CO2减排最具潜力的现实选择.CO2-EOR(Enhanced Oil Recovery)方法适用于油田开发晚期,通过把CO2注入到比较稳定的油藏,一般可提高油藏采收率达10%～15%;另外把CO2注入到气田中,实施CO2-EGR(Enhanced Gas Recovery).一方面,接近枯竭的气田在没有地层水入侵之前具有巨大的埋存能力,为CO2提供巨大的埋存空间;另一方面注入CO2后,使地层重新增压保持储层中原始的压力,可以保持储层的完整性和安全性.同时,原有的油气圈闭可作为良好的埋存箱能有效地阻止CO2泄漏,使部分CO2能永久地埋存于地下.此外,也可以把CO2注入到煤层中,实施CO2-ECBM(Enhanced Coalbed Methane Recovery),利用煤层对CO2和煤层气(主要为甲烷)吸附能力的差异,实现CO2排替CH4,提高CH4的采收率.

Geological Storage of CO2 and Commercial Utilization

Injecting CO2 into the subsurface oil and gas reservoirs and coal-beds, at the moment, is the most realistic choice in reducing the CO2 emission into the atmosphere, which can not only enhance the recoveries of the oil and gas, and coal bed methane, but also can sequestrate partial CO2 within the subsurface reservoirs and coal beds permanently. CO2 enhanced oil recovery (CO2 -EOR) is generally performed in the late stage of oil exploration and development, by which CO2 is injected into the oil reservoirs to enhance the oil recoveries, in general, up to 10-15% by volume. Similarly, CO2 enhanced gas recovery (CO2 -EGR) is to inject the CO2 into the gas reservoirs to enhance the gas recoveries. The extracted gas reservoirs can provide voluminous pore spaces for CO2 storage prior to flooding by formation waters. In this case, Injecting CO2 into the subsurface gas reservoirs would increase the reservoir pressure and maintain the primary formation pressure, which can keep the integrity and reduce the damage of reservoirs. In the meantime, the traps of oil and gas pools are also good compartments from which leakage of injected CO2 is prevented, such that the CO2 is sequestrate in the subsurface permanently. In addition, the CO2 can also be used to enhance the recovery of coalbed methane by injecting CO2 into the coalbeds (CO2 -ECBM), due to the differences in coal adsorption for CO2 and CH4. Higher absorption of CO2 related to CH4 by coals would result in the displacement of CH4 by CO2 in place, thereby enhancing the recovery of coalbed methane when the CO2 is injected into the CH4-bearing coalbeds.