Joule–Thomson (JT) cooling of injected CO₂ can significantly impair well injectivity through hydrate formation, salt precipitation, and viscosity increases. These risks impose operational constraints on injection rates during CO₂ storage projects. This study develops and analyses three analytical models that describe temperature evolution during CO₂ injection into porous media under different heat exchange regimes with surrounding formations. The models account for (i) steady-state heat exchange governed by Newton’s law, (ii) non-steady-state heat exchange initiated by the CO₂ front, and (iii) non-steady-state heat exchange initiated by the thermal front. Exact solutions were derived and validated against a quasi-two-dimensional benchmark solution.

The developed models capture temperature propagation for different reservoir boundary conditions, allowing for pressure–temperature trajectories to be mapped onto the CO₂–water phase diagram. This framework enables direct assessment of hydrate formation by evaluating which sections of the injection zone will enter the hydrate stability zone of the phase diagram. Results indicate that higher injection rates intensify JT cooling, giving rise to a maximum safe injection rate that avoids hydrate formation. Adjusting CO₂ injection temperature and rate can significantly alter the P-T trajectory of each well, either preventing hydrate formation entirely or ensuring that any hydrates form only at a sufficient distance from the injection well to avoid injectivity impairment.

The analytical framework provides practical guidance for assessing injection strategies under various geological conditions. By linking injection rate, temperature, and reservoir thermal architecture, the models allow operators to minimise hydrate-induced formation damage and permeability decline. The approach also offers a rapid and transparent method for selecting appropriate heat exchange models, reducing reliance on computer simulations. Application to the Sleipner and Gorgon CO₂ storage projects demonstrates practical relevance for field-scale CCS, supporting reliable and cost-effective planning of large-scale CO₂ storage.