A system for methane hydrate-bearing sediment detection with pressure is designed, series of experiments for compressional wave response of hydrate-bearing sands are performed systematically in laboratory. Considering the difficulties in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples. The system is designed to achieve in situ hydrate formation in bearing sediments and synchronous acoustic detection and signal analysis. The hydrate formation unit comprises a pressure chamber which is designed for pressure core analysis, a high-precision pump for gas injection. The ultrasonic test unit consists of a pulse transceiver, an A/D converter, an ultrasonic transducer, a signal amplifier and an oscilloscope. The influence factors, including hydrate saturation and formation process to P-wave velocity (Vp) and amplitude are investigated. The results show that Vp and amplitude both increase with the hydrate saturation. Vp exhibit relatively minor changes when hydrate saturation varies from 0% to 40% compared to the P-wave amplitude. However, there is a close relationship between the velocity of P-wave and the saturation of hydrate which could be the effective criterion for the hydrate formation in bearing sediments.
Keywords ultrasonic test; gas hydrate sediment; P-wave velocity; hydrate saturation