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The acoustic properties of gas hydrate-bearing unconsolidated sediments has significance in marine gas hydrate exploration and resource evaluation. In this paper, a new type of bender elements were proposed to measure both compressional wave velocity (Vp) and shear wave velocity (Vs) of hydrate-bearing unconsolidated sediments simultaneously under certain pressure and temperature conditions. Combination of Fast Fourier Transform (FFT) and Wavelet Transform (WT) was thought to be an effective method to analyze both Vp and Vs data, based on which several runs of experiments were conducted. The results show that the new bender element technique is efficient in detecting gas hydrate formation and dissociation in unconsolidated sediments. The acoustic velocities of hydrate-bearing unconsolidated sediments increase with hydrate saturation (Sh) as follows. When Sh is less than 25% or more than 60%, Vp and Vs increase rapidly with Sh, which indicates that hydrate may cement sediment particles. However, when Sh is between 25% and 60%, Vp and Vs increase little, which indicates that hydrate may partly contact with sediment particles. |
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