二氧化碳咸水层封存和利用

 CO₂咸水层封存是减少人为CO₂排放最有效的选择之一,是人工制造巨量碳汇的新型地质工程。全球商业化规模CO₂封存项目和中试尺度的现场试验10年以上的平稳运行表明,CO₂咸水层封存在技术上是可行的。本文从CO₂咸水层的封存机制、储量评价、监测和预测、安全评价和利用方面作了系统评述。水热实验和数值模拟是目前水-岩-CO₂相互作用过程和CO₂封存机制研究的重要方法,但需要现场试验数据的验证。储量评价主要基于CO₂溶解捕获原理,参数的确定方法及不同尺度上方法的选择仍需进一步研究。以地震法为代表的地球物理方法能够有效监测储层中CO₂晕的形态,但价格昂贵不宜广泛应用,新方法的试验很有必要；地球化学方法能够及时反映CO₂注入后的运移及储层的响应,简单易行,成本较低,但需要监测孔；数值模拟方法能为CO₂晕的运移形态和方向提供依据；需要依托一套适用性强的多种方法联用监测技术。安全评价技术包括数值模拟、岩石力学参数测定及各种模型建立,还需从公众认可度及加入大规模项目数据角度提高和完善。考虑到成本问题,CO₂咸水层利用值得重视,特别是实现地热可持续开发利用的CO₂-EATER技术的发展。国外在CO₂海相咸水层封存的技术发展较快,国内沉积盆地可用于CO₂封存的咸水层多以陆相沉积为主,储层水化学、水文地质和矿物岩性特征与海相咸水层有很大差异,非均质性也较突出,需要在借鉴和学习国外经验的同时突出自己的特色和重点。

CO2 Sequestration and Utilization in Deep Saline Aquifers

CO₂ sequestration in deep saline aquifers is one of the most effective and promising choices to mitigate anthropogenic CO₂ emissions. Commercial scale CO₂ injection projects and pilot scale field tests have demonstrated that it is technologically feasible. The state of the art and future challenges including CO₂ trapping mechanism, capacity assessment technology, monitoring technology, safety assessment technology, and utilization technology are discussed based on the review of existing literatures. Hydrothermal experiment and numerical simulation in particular have proven to be very important methods to study the water-rock-CO₂ interaction process and mechanism supported by field tests. Geophysical methods, seismic monitoring methods, in particular 4D, cross well and vertical seismic, could effectively detect the CO₂ plume in reservoirs. However, they are unable to be widely applied due to the high cost, meanwhile geochemical methods (e.g. water chemistry and isotopes) could reflect reservoir responses in time after CO₂ injection which is simple with low cost, and numerical simulation could provide the basis for CO₂ plume migration. It is suggested that a set of multi-methods monitoring technology with easy operations should be established. Safe assessment technology includes numerical simulation, mechanical parameters testing, and establishment of various models; and further consideration of public acceptance and practical experience from large-scale CO₂ storage projects need to be integrated for the improvement. Considering the high cost of CCS implementation, CO₂ utilization should be encouraged and in particular, the CO₂-EATER technology needs to be further discussed in order to improve waste geothermal water injectivity and sustainable development of geothermal resources. Technologies and methods of CO₂ sequestration in marine saline formations develop very fast abroad, in the meantime most of the sedimentary basins in China that are suitable for CO₂ sequestration are continental deposition with great differences in formation water and reservoir rock compositions and in this way, it is important and necessary to emphasis our specialty and focus when learning from experiences abroad.