Adaptability Analysis of <scp> CO ₂ </scp> Storage in Depleted Tight Sandstone Gas Reservoirs

ABSTRACT The Sulige Gas Field, currently in the late‐stage depletion phase, exhibits substantial potential for CO 2 storage. An integrated evaluation methodology was developed, incorporating CO 2 caprock pressure breakthrough tests, CO 2 –water–rock interaction experiments, and CO 2 storage simulation experiments to assess the suitability of depleted tight sandstone reservoirs for CO 2 sequestration. Key findings include: (1) The minimum caprock breakthrough pressure was determined to be 30 MPa, confirming sufficient sealing capacity; however, horizontal breakthrough risks were found to exceed vertical ones. (2) Dissolution of minerals (calcite, chlorite, and illite) was observed, whereas the caprock pressure‐bearing limit remained unchanged at 30 MPa; minor increases in reservoir porosity and permeability were also detected. (3) A negative correlation between water saturation and storage efficiency was quantified, indicating that intermittent injection could mitigate pressure buildup and enhance storage capacity. A novel methodology for CO 2 storage capacity estimation has been developed in this study. Application of this approach to the He 8 Member and Majiagou Formation reservoirs in the Sudong Block yields a total estimated CO 2 storage potential of approximately 123.9 million tones. This study confirms that sandstone caprocks can effectively confine CO 2 , highlighting the high suitability of depleted tight gas reservoirs for large‐scale CO 2 sequestration.