深部咸含水层CO_2注入的流体迁移模拟研究——以松辽盆地三肇凹陷为例

Fluid migration modeling of CO_2 injection in deep saline aquifers-A case study of the Sanzhao Depression,Songliao Basin

CO2地质封存是减少温室气体向大气排放的有效措施之一,而深部咸含水层CO2地质封存是目前可行的最有潜力的封存技术。先前研究表明,松辽盆地是一个潜在的封存场地。基于对松辽盆地地质资料的初步分析,选取三肇凹陷的姚家组1段和青山口组2、3段地层作为CO2的注入层,建立一个典型二维模型,研究CO2注入后的迁移规律。结果表明,CO2注入后会向上和侧向迁移,后期可能出现的对流作用能促进CO2的溶解。残留气体饱和度、注入层水平和垂直渗透率的比值对模拟结果影响最大。此外,储层中的薄页岩夹层有利于CO2的溶解,因此,在保证注入性和封存量的情况下,储层中低渗透性夹层是允许的。

CO_2 geological storage is one of effective measures for reducing emissions of greenhouse gases, and now CO_2 disposal in deep saline aquifers becomes a feasible and most promising technology for CO_2 storage. The previous studies show that the Songliao Basin is one of potential and promising storage sites. Based on the preliminary study of geological formation of the Songliao Basin, the first member of the Yaojia formation, the second and third members of the Qingshankou formation in the Sanzhao Depression are selected as the suitable aquifers for CO_2 injection. Then a generalized twodimensional modebis set up to characterize the injection of CO_2 into the Yaojia and Qingshankou formation, and to investigate the migration of CO_2 in the aquifers. The results of model show that CO_2 would migrate upwards and spread laterally over time after injection; and the phenomenon of convective mixing could occur obviously later, which could enhance the dissolution of CO_2process. The residual gas saturation and the ratio of horizontal to vertical permeability have the greatest effects on the results of model. Besides, the interbedded shale layers in the reservoir can enhance the dissolution of CO_2. It＇s suggested that the reservoirs with lowpermeability intercalation could be allowed when the injectivity and storage capacity are guaranteed.