Abstract:  The Songliao basin, a vital energy and industrial base in China, has substantial CO2 emissions and abundant underground saline water, possessing potential for CO2 geological sequestration. To enable the scientific selection of sites for CO2 geological storage in saline aquifer and to systematically evaluate the storage suitability of this region, this study focuses on the Central depression of Southern Songliao basin, analyzing the engineering geological conditions, sequestration potential, and socioeconomic conditions with a geographic information system (GIS) based multi-criteria decision analysis (MCDA) approach. Firstly, an evaluation indicator system comprising 3 primary indicators and 31 secondary indicators was established. Secondly, GIS was used to generate a 1 km-resolution raster layer of the data for each evaluation indicator. Then, reclassify the raster data according to the classification criteria. Finally, the raster layers for each indicator were overlaid with weighted values based on the weights determined by the analytic hierarchy process (AHP) and generate a  suitability map for CO2 geological storage in saline aquifers in the Central depression area of the southern Songliao basin. The results indicate that suitable areas are mainly located in the northern portion of the Honggang terrace and the southwestern part of the Changling depression, accounting for approximately 24.0% of the total regional area. Unsuitable areas are concentrated in the Fuxin uplift, accounting for only 6.8% of the total regional area. In total, nearly 56.0% of the area is suitable or relatively suitable for CO2 geological sequestration in saline aquifers. More than half of the areas within the Central depression in the southern Songliao basin meet the fundamental requirements for CO2 geological storage in saline aquifers. Further optimization and engineering deployment can proceed.

Key words: Songliao basin, CO2 geological storage in saline aquifers, analytic hierarchy process, GIS, suitability assessment, carbon neutral