苏北盆地油田封存二氧化碳潜力初探

Preliminary Estimation of Carbon Dioxide Storage Capacity in the Oil Reservoirs in Subei Basin

油田二氧化碳封存是减少温室气体排放量最有效的途径之一,油藏中封存CO2主要有构造地层储存、束缚气储存、溶解储存和矿化储存等四种方式,CO2在油藏中的地质储存容量采用国际上通用的资源储量金字塔理论来进行潜力评价。本文通过分析油田CO2封存机理,结合江苏省苏北盆地的地质和构造条件,对苏北盆地油田进行CO2封存潜力研究。苏北盆地油田多为低渗透和含水油藏,在储存CO2的潜力上,东台坳陷优于盐阜坳陷,次级单元中又以高邮凹陷、金湖凹陷封存CO2潜力最大,一系列小型构造单元比较适合于CO2封存,并有利于后期的保存。在封盖能力上,苏北盆地在垂向上有明显的两分性,下部上白垩系和古新统盖层相对上部始新统盖层对CO2封盖性更好。估算得到苏北盆地油田埋存CO2的理论储存容量为1.5054×108t,有效储存容量为0.0828×108t～0.4421×108t,表明苏北油田封存CO2的潜力较大。

The CO2 storage in oil reservoirs is one of the most effective ways of reducing the greenhouse gas emission, which is based on the mechanisms of structural and stratigraphic trapping, residual gas trapping, dissolution trapping and mineral trapping. The universal pyramid method is introduced to assess the CO2 storage capacity for the oil reservoirs. Subei basin has many oil reservoirs with low permeability and water content. Dongtai sag is better than Yancheng-Funing sag on the CO2 storage potential. Gaoyou depression and Jinhu depression have the greatest potential of CO2 storage among the secondary geological units. A series of the small tectonic units in this area are more suitable for CO2 storage, and beneficial to the preservation of late stage. Subei basin has obviously vertical dichotomy on the sealing ability of CO2 storage. The lower cap rocks of upper Cretaceous system and Paleocene series have better sealing capabily than the upper cap rocks of the Eocene epoch. Based on analyzing the mechanism of CO2 storage in oil reservoirs and combining with geological and structural conditions of Subei basin, we estimated that the theoretical storage capacities of CO2 is 1.5054×10^8t t and the effective storage capacities of CO2 is 0.0828 ×10^8t t - 0.4421×10^8t t, which shows the great potential of CO2 storage in Subei basin, Jiangsu Province.