Abstract: This study investigates the CO₂ sequestration potential of carbonate reservoirs under the coupled effects of the solubility carbon pump and the carbonate pump, as well as its variation with burial depth. A high-pressure autoclave system was used to simulate water-limestone-CO₂ interactions, reproducing karst processes under temperature and pressure conditions equivalent to depths of 200 m-1 200 m. The amounts of dissolved and mineralized CO₂ sequestered were measured. Based on the experimental data, a predictive model for CO₂ sequestration was established using Henry's law and the van't Hoff equation. This model was then applied to estimate the CO₂ storage capacity of a hypothetical depleted carbonate oil and gas reservoir with a volume of 5×10⁵ m³, a porosity of 10%, and a water saturation of 50%. The results indicate that increasing burial depth elevates reservoir pressure, which not only enhances CO₂ solubility but also accelerates carbonate rock dissolution, thereby reinforcing the synergistic effect of the two carbon pumps and improving carbon sequestration efficiency. As the depth increases to the point where CO₂ enters a supercritical state, both its solubility and the dissolution-precipitation dynamics within the system are further enhanced. In the hypothetical depleted reservoir, the total CO₂ sequestration, mineralized sequestration, and dissolved sequestration increased from 3.23 t to 23.97 t, from 2.18 t to 18.98 t, and from 1.05 t to 4.99 t, respectively, when the depth increased from 200 m-300 m to 1 100 m-1 200 m. This study demonstrates that mid-deep carbonate reservoirs possess an enhanced CO₂ dissolution-mineralization storage capacity under increasing pressure, providing experimental support for various karst-related carbon sinks, particularly for CO₂ sequestration in depleted carbonate oil and gas reservoirs.