ABSTRACT

Full waveform logs from the Nankai Trough off central Japan are used to estimate both compressional and shear attenuation in gas hydrate bearing sediments. The high attenuation of the compressional waveforms and high attenuation of the shear waveforms correlate well with the presence of gas hydrate inferred from the resistivity log. On the other hand, we observed the high attenuation of the compressional waveforms and low attenuation of the shear waveforms below the gas hydrate stability zone. This can be explained by the presence of partially gas-saturated sediments. We concluded that sonic attenuation from both monopole and dipole waveforms should give new insight to characterize gas hydrate bearing sediments and gas-saturated sediments.

Keywords:
free gas, upstream oil & gas, attenuation measurement, guerin, compressional waveform, well logging, reservoir characterization, dipole waveform, log analysis, sonic full waveform log
Subjects:
Reservoir Characterization, Formation Evaluation & Management, Seismic processing and interpretation, Open hole/cased hole log analysis
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2004. Society of Exploration Geophysicists
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