Abstract
AbstractSeismic attenuations of different types of gas hydrate deposition in fluid‐saturated porous solids are discussed. The affecting factors on estimation of gas hydrate and free gas saturations are analyzed. It is found that the porosity of the sediment, the compressional‐wave velocity model and methods of calculating elastic modulus are key parameters in the estimation of gas hydrate and free gas saturations. Seismic attenuation of gas hydrate‐bearing sediment is closely related with the types of gas hydrate deposition. Negative anomalies of quality factors indicate that gas hydrate deposits are away from grains as a part of interstitial fluid. Positive anomalies of the quality factors indicate that gas hydrate contacts with solid and changes the solid bulk and shear moduli. Low frequency velocity and high frequency velocity are used to estimate gas hydrate and free gas saturations in Blake Ridge according to the well log data at Hole 995 in ODP leg 164. Gas hydrate saturation obtained by low frequency velocity is 10%~20% of the pore space and free gas saturation is 0.5%~1% of the pore space. While gas hydrate saturation obtained by high frequency velocity is 5%~10% of the pore space and free gas saturation is 1%~2% of the pore space.
Published Version
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