Large-scale physical simulation is essential for advancing our understanding of natural gas hydrates exploitation mechanism. However, cylinder-shaped simulators often face challenges in balancing large volume, controllability, and comprehensive monitoring. In this study, we developed a fan column-shaped hydrate simulator (FCHS) with an internal angle of 6°, a radius of 3 m, and an inner height of 0.3 m, resulting in an effective volume of ~142 L. Moreover, the FCHS is equipped with an integrated "thermal-pressure-acoustic" sensing system, enabling in-situ monitoring of temperature, pressure, and P-wave velocity evolution during hydrate formation and dissociation process. The experimental results indicate that a pressure gradient successfully established from the reservoir center toward its boundaries during depressurization stage, and pressure propagation is relatively slow, resulting in a radial pressure difference of 3–4 MPa within a 3 m range. Once the system reaches pressure equilibrium, the pressure difference decreases to 0.3–0.4 MPa. The depressurization at the wellbore promotes hydrate dissociation in the near-well region, resulting in the radial temperature difference reaches ~1.5 ℃ along the radial direction. The acoustic data reveals that a radial gradient in hydrate saturation gradually forms from the center to the boundary during depressurization-induced gas production. The evolutions of spatio-temporal multi-fields obtained in the FCHS are consist with that of field production. The FCHS proves to be a cutting-edge platform for experimental simulation of NGH exploitation and carbon sequestration processes.

Understanding the acoustic characteristics of hydrates in various sediments is crucial for hydrate resource detection and safe and efficient exploitation, as hydrate occurrence patterns vary greatly in different sediments. In this work, sediments with different bentonite contents, water saturations, and types were prepared to investigate the characteristics of P-wave velocity (reflecting the magnitude of hydrate saturation in the sediment) and amplitude (reflecting the degree of hydrate-sediment cementation) during hydrate formation and depressurization. During hydrate formation, the P-wave velocity and amplitude have similar trends. As clay content increases, the P-wave velocity increase rates quickened. On the other hand, the increased rate of P-wave velocity slows down with the increase of water saturation in the clay-bearing sediments. Comparing various types of sediment shows that the water absorption and swelling of bentonite reduce the pore space, speeding up the cementation of the hydrate with the sediment and increasing P-wave velocity at a faster rate. Correspondence between P-wave velocity and hydrate saturation is strongly related to sediment type, clay content, and water saturation. The rapidly decreasing amplitude in the early stage of hydrate depressurization indicates that hydrate in clay-bearing sediments is weakly cemented to the sediments, which is prone to stratigraphic instability. The findings of this study offer guidance for hydrate resource assessments in clay-bearing sediments as well as geologic risk estimations during hydrate mining.