Phase equilibria of gas hydrates: A review of experiments, modeling, and potential trends

Phase equilibria is a fundamental property for the applications of gas hydrate technologies including but not limited to energy exploration and exploitation, gas storage and separation, flow assurance, desalination, and carbon sequestration. To date, an overwhelming number of relevant experimental and theoretical studies have been conducted. Thus, we presented a comprehensive review of the work on hydrate phase equilibria published over the years. First, we summarized and discussed the different measuring methods, focusing on the PVT and differential scanning calorimetry (DSC) techniques, as well as their applications in various systems to establish a quantitative framework for gas hydrate phase equilibrium analysis. Some modifications and innovative approaches ae also highlighted. To have consistency in the topic of hydrate phase equilibria, we then turned our focus on the modeling work together with some state-of-the-art machine learning algorithms and discussed their major contributions to the improvement of hydrate phase equilibrium predictions. This was followed by a brief review of the (semi-) empirical correlations focusing on calculating hydrate stability boundaries over wide pressure or inhibitor ranges. Given the space limitations of this review, several foundational and excellent review works and books were also cited accordingly. Finally, we briefly discussed the limitations and perspectives in the near future at the end of each section to provide readers with comprehensive insights that may motivate further work in this promising field.