Inclusion Effect of Thermal Stimulation on the Cyclic Depressurization Process for Gas Hydrate Production Using X-ray Computed Tomography Image Analysis

A combined cyclic depressurization method was introduced to enhance the productivity and sediment stability for gas hydrate (GH) production. Specifically, the impact of including thermal stimulation on the cyclic depressurization process with a constant and low depressurization rate was investigated using X-ray computed tomography (CT) image analysis. To imitate the natural geological existence of GHs, a GH sample was prepared using the excessive water method by reflecting the harsh equilibrium conditions of the Ulleung Basin. The GH production results were obtained by inserting the cyclic depressurization and thermal cyclic depressurization stages of the entire depressurization process in a core-scale cell. The GH dissociation pattern was obtained in real time, and the degree of GH dissociation and production was quantified via an X-ray CT image analysis. In this study, we confirmed that supplementary thermal stimulation in the cyclic depressurization stage considerably enhanced the gas production rate compared to solely implementing the cyclic depressurization stage. In addition, the cyclic depressurization with a constant and low depressurization rate ensured sediment stability even after completing the thermal stimulation process. Therefore, this combined method will provide insights to solve the challenges of decreasing productivity and insufficient sediment stability for long-term GH production technology.