Abstract:

In many mechanisms of the geological storage of CO₂ in deep saline aquifers, the trapped gas storage has great potential, which accounts for about 30% of the total storage. Residual gas saturation is a very important parameter to evaluate storage capacity of trapped gas.This thesis can qualitatively evaluate storage capacity of trapped gas in different saline aquifers and provide basic parameters for assessing of storage capacity in deep saline aquifers by measuring residual CO₂ saturation of different components of saline flooding CO₂. At the same time, it can give some guidances and references in choosing the project site and the target aquifer of the geological storage ofCO₂in deep saline aquifers. We used distilled water,NaCl solution, CaCl₂ solution and the mixture of NaCl and CaCl₂ solution (the mass ratio is 1∶1), which were all saturated by CO₂ and the mass concentration of all solutions is 10%, to inject into CO₂ saturated core and finally we calculated residual CO₂ saturation. The injection process can be divided into two phases:piston drainage, portable drainage. Experimental results show that the ascending order of residual CO₂ saturation of four kinds of liquid flooding is distilled water, the mixture solution, NaCl solution and CaCl₂ solution. The results indicate that interfacial tension plays a dominant role in the injection process under the influence of interfacial tension and fluid viscosity. Among the three types of saline, storage potential of trapped gas of Cl-Ca-type water is maximum, followed by Cl-Na-type water. The potential of Cl-Na·Ca-type water is minimum.

Key words: geological storage, trapped gas, residual CO₂ saturation, interfacial tension, fluid viscosity