Uncertainty assessment of carbon dioxide storage capacity evaluation in deep saline aquifer:a case study in Songliao Basin, China

Carbon dioxide Capture and Storage techniques (CCS) are one of the effective measures for reduction Carbon dioxide emissions to the atmosphere to mitigate the global warming. Among the Carbon dioxide geological storage options, deep saline aquifers offer the largest storage potential and are widely distributed throughout the Earth. Implementation of carbon dioxide capture and geological storage to reduce greenhouse gas emissions requires carbon dioxide storage capacity in deep saline aquifers. The storage capacity estimation depends on the storage trapping mechanisms and the availability, resolution and certainty of data. There are five different types of trapping mechanisms in deep saline aquifers namely structural and stratigraphic trapping, residual gas trapping, solubility trapping, mineral trapping and hydrodynamic trapping in which storage capacity by solubility trapping is the largest. The carbon dioxide storage capacities in deep saline aquifer can be evaluated by the method recommended by Carbon Sequestration Leadership Forum (CSLF), which mainly depends on the area of study area, thickness and porosity of sandstone, density and carbon dioxide content (mass fraction) in formation water at initial and saturated state. Hydrogeological parameters in aquifer are uncertainty because of uncertainty of measurement and the spatial variety, which leads evaluation uncertainty of carbon dioxide storage capacity. In this paper, acceptance of evaluated carbon dioxide storage capacity in deep saline aquifer caused by hydrological parameters was discussed based on geostatistical methods and stochastic simulation. The stratum named Yaojialing group in the center depressed area of Songliao Basin was chosen as study area because of the rich data. The porosity of sandstone, thickness ration of sandstone to stratum and the total dissolved solid in formation water were regarded as the main source of the uncertainty of carbon dioxide storage capacity evaluation in deep saline aquifer. Based on the best model of semi-variance function of these three hydrogeological parameters determined by GS+9.0 test version, 100 simulations were implemented for each hydrogeological parameters with Sequential Gaussian Simulation(SGS). One hundred sets of the hydrogeological parameters were rand chosen, and the corresponding carbon dioxide storage capacities in the deep saline aquifer were evaluated with the CSLF's method coupled other parameters. The evaluated carbon dioxide storage capacities in Yaojialing Group were lognormal distributed, and the minimum, maximum, average and standard variance values were 1956Mt, 7949Mt, 3288Mt and 1182Mt, respectively. If the average of all hydrogeological parameters were used, the evaluated value was 2721Mt. Compared to other determining methods of hydrogeological parameters, the stochastic methods is more reasonable for the evaluation of carbon dioxide storage capacities.