Near-wellbore hydrate effect on CO2 injection: insights from microfluidics and core flood experiments

Understanding CO2 hydrate formation near the injection wellbore is critical for improving the safety and efficiency of geological CO2 storage. Hydrate formation can significantly reduce rock permeability and impair injection performance, yet its pore-scale behavior and impact under realistic reservoir conditions remain insufficiently understood. This study combined microfluidic and core-flood experiments to investigate hydrate morphology, formation dynamics, and their effects on injectivity. Microfluidic chips with well-characterized pore structures were used to directly observe hydrate structures under gaseous and liquid CO2 phases, which reveal eight distinct morphologies, including pore-filling, load-bearing, cementing, grain-coating, patchy, worm-like, laminated-like, and banded-like forms where resulted in hydrate saturations reaching up to 15%. Complementary core-flood experiments on rock samples with permeabilities ranging from 0.004 to 2 Darcy employed high-resolution X-ray CT imaging to monitor CO2 and water saturations dynamically. Results indicated that lower permeability cores showed faster hydrate formation and higher saturation increases (up to 16%), which is consistent with microfluidic findings. This multi-scale experimental approach provides deeper insight into hydrate behavior under field-relevant conditions and its influence on CO2 injectivity and offers valuable guidance for optimizing injection strategies in geological carbon storage.