Evaluation system of CO₂ geological storage site in low porosity and low permeability saline aquifers—A case study of Ordos Basin

【Objective】 As an underground space resource, the deep saline formation is an important site to implement CO₂ injection and geological storage, which is a necessary means to achieve the goal of greenhouse gas emission reduction and carbon neutrality. The site selection and potential evaluation of CO₂ aquifer reservoir geological storage are mostly at the macro basin level and regional level, and the site selection evaluation system has not considered the suitability of low porosity and low permeability strata. 【Method】 Based on the well logging data of 192 Wells in Yusheng area, Ordos Basin, this paper carries out the formation division and correlation, lithology and physical property interpretation of non-oil and gas reservoirs and identifies the aquifer reservoirs. Then, based on the study of the formation characteristics, seal property, sealing potential and surface environment, an evaluation index for the location of geological storage of deep saline CO₂ reservoirs considering the development characteristics of low porosity and low permeability reservoirs is proposed and quantified.【 Result and Conslusion】 The proposed first-level evaluation indexes are geological storage conditions, storage capacity conditions and social environmental conditions, which represent the injectivity, storage ability and surface feasibility respectively. The geological storage conditions include the second-level evaluation indexes such as reservoir lithology, reservoir thickness, porosity and permeability. The conditions of storage capacity include second-level evaluation indicators such as closure of cap layer, buried depth, storage potential, fracture, etc., while the social environment conditions include second-level evaluation indicators such as the status of underground resource development, land use status, collapse and disaster area, source-sink matching, and public acceptance. The established site selection evaluation system for target and site level CCS projects based on the current situation of low porosity and low permeability sandstone reservoirs in Ordos Basin will provide guidance for constructing the industrial CO₂ aquifer geological storage projects.