Dynamic characteristics of CO₂ hydrate formation and spatiotemporal evolution of reservoir parameters during flow...

The hydrate-based geological storage of CO₂ is a highly promising method, wherein CO₂ is injected into a reservoir and flows through it to form hydrates, leading to high density and stable storage. However, the storage capacity cannot be directly measured, and existing research lacks a direct approach to predict the dynamic behavior of CO₂ hydrate formation. In this study, a prediction model for the dynamic formation of CO₂ hydrate and a prediction model for the spatiotemporal evolution of gas pressure and hydrate saturations during flow are presented through experimental studies. Experiments were conducted at different gas flow rates in six cores with different hydrate saturations (19.91%-34.42%). The results revealed a dual-role mechanism of gas flow rate in hydrate formation. Higher flow rates (from 0.03 ml/s to 0.13 ml/s) reduced overall hydrate formation by 40.8% and water conversion by 28% due to shortened gas-water contact time. Conversely, they enhanced nucleation kinetics, decreasing induction time by 71.4% via increased contact frequency. The results elucidate the role of gas flow in porous media in regulating hydrate nucleation and mass transfer, a process insufficiently addressed by conventional kinetic models. Therefore, a dynamic prediction model for hydrate formation was established, expressed as N(t) = N₀·e^b/(t + c), which incorporates key hydrate formation parameters and gas flow rate conditions. The predicted values exhibited errors primarily within ±5%. Additionally, our study demonstrated a relationship between hydrate-induced permeability reduction and dynamic inlet pressure evolution. By coupling experimental conditions with permeability models, the spatiotemporal evolution of pressure and hydrate saturation during gas flow is dynamically predicted. This study provides a crucial theoretical foundation for predicting the dynamic behavior of hydrate formation.