Efficient exploitation and carbon storage efficiency of shale condensate gas reservoirs

Condensate gas reservoirs with ultra-high gas condensate content (> 600 g/m³) tend to undergo rapid retrograde condensation when reservoir pressure falls below the dew point pressure. This leads to condensate liquid accumulation in near-wellbore zones, thereby seriously impacting gas well productivity. In this study, we investigate the condensate gas reservoirs with ultra-high gas condensate content in block X. While considering the adsorption-diffusion mechanisms specific to shale condensate gas reservoirs, we investigate the role of CO₂ injection for energy replenishment on reducing condensate liquid content and restoring well productivity. It also evaluates the carbon storage efficiency across various CO₂ sequestration forms. The results indicate that during depletion recovery, continuous production of light components shifts the reservoir fluid system from a condensate gas state to volatile oil. Injecting CO₂ at the low-pressure production stage can effectively reduce condensate liquid content in the formation and restore gas mobility in the near-wellbore zone. In contrast, injecting CO₂ at the high-pressure production stage transforms the system into a volatile oil state, thereby increasing the condensate liquid volume instead. For condensate gas reservoirs with ultra-high gas condensate content, CO₂ injection fails to significantly reduce the dew point pressure. In contrast, in condensate gas reservoirs with medium or low gas condensate content, CO₂ injection can effectively lower the dew point pressure, thereby mitigating retrograde condensate pollution. CO₂ sequestrated underground through structural and residual trapping mechanisms constitutes the dominant proportion of total storage, while that sequestrated via dissolution and adsorption trapping accounts for comparatively minor proportions. Additionally, the injection and production parameters, including injection duration, injection rate, and soaking time, for the single-well CO₂ huff-n-puff process are optimized, providing a theoretical basis for the efficient exploitation of and carbon sequestration in shale condensate gas reservoirs with ultra-high gas condensate content.