Pressure effects on heat transfer in hydrate-bearing deposit with drilling fluid invasion by lab simulation

Natural gas hydrate is a potential green energy resource widely distributed in tundra or offshore layers. During deepwater drilling in hydrate-bearing layers, certain artificial operation will induce hydrate to break down, causing the disasters such as landslide, collapse, and blowout. The heat and mass transfer in layers is the key point to predict and control these risks, but difficult to be described due to phase transition. In this study, a series of experiments have been designed to simulate hydrate-bearing deposits with drilling fluid invasion under different pressure. The initial pressure in wellbore and pore were adjusted separately, and the real-time temperature at different positions were monitored. The results implied that a higher wellbore pressure can promote invasion, but its effect is limited by the distance from the wellbore. Initial pore pressure mainly influenced the phase equilibrium critical temperature. Since the dissociation gas contra-streaming into wellbore will further accelerate hydrate dissociation, a reasonable wellbore pressure should be optimized, which is conductive to the drilling safety.