Experimental Study on Temperature-Pressure Response Laws of Natural Gas Hydrate Formation and Dissociation

As a potential strategic alternative energy source for the future, the safe and efficient drilling and production of natural gas hydrate(NGH) is the core of current research. During the drilling and production process, changes in the wellbore temperature-pressure field can easily trigger the secondary formation or dissociation of NGH, leading to major risks such as wellbore blockage and pressure loss of control. To address this issue, this study independently developed an experimental system consisting of four core modules: gas supply, high-pressure reaction, constant temperature control, and data acquisition. Systematic experiments on the formation and dissociation of methane hydrate under different initial temperatures (3 ~ 15 °C) and initial pressures (5 ~ 15 MPa) were conducted to accurately determine their phase equilibrium conditions. The experimental results show that there is a significant “induction time” during the NGH formation process, resulting in the apparent formation pressure being higher than the true phase equilibrium pressure. However, this phenomenon does not exist in the dissociation process, and the dissociation pressure is more representative of the true phase equilibrium conditions. Based on the dissociation experimental data, the phase equilibrium curve and empirical equation of NGH in the study area were fitted, clarifying the synergistic control effect of temperature and pressure parameters. In addition, the experiment revealed typical temperature-pressure variation characteristics during NGH formation and dissociation, such as the “temperature rise-pressure drop” phenomenon during formation and the “temperature drop and pressure rise” phenomenon during dissociation. This study provides key experimental data and a theoretical basis for the prediction and safety control of multiphase flow obstacles in NGH drilling and production wellbores.