Experimental Study on Phase Equilibrium of Condensate Gas Hydrates and Establishment of Prediction Model

To solve safety issues such as pipeline blockage caused by hydrate formation during offshore condensate gas development, this study conducted experimental research on the phase equilibrium of condensate gas hydrates and established a high-precision phase equilibrium prediction model. Using the constant-volume temperature cycling method, the influence laws of gas components (Gas Sample 1, Gas Sample 2) and liquid-phase systems (pure water, single inhibitors, mixed inhibitors) on hydrate phase equilibrium conditions were systematically investigated on a self-built high-pressure experimental device. Based on the Chen-Guo model, considering temperature, pressure, water activity, and gas component characteristics, a phase equilibrium prediction model for condensate gas hydrates was established. The prediction accuracy was improved by modifying the equation of state and activity calculation method, and corresponding prediction software was developed. The results show that C2+ heavy hydrocarbons and CO2 significantly enhance hydrate stability; the inhibition effect of 10 wt% single inhibitors follows the order: NaCl ≈ Methanol > Ethylene glycol, and the inhibition effect of mixed inhibitors is weaker than that of single inhibitors at the same concentration. The maximum prediction error of the established model is less than 0.891 MPa, and the relative error is less than 10%, which is superior to the commercial software PVTsim. This study can provide theoretical support and engineering reference for hydrate prevention and control in offshore condensate gas fields.