HR: 1340h
AN: OS23A-1066    [Abstracts]
TI: Calibration and analysis of methane hydrate beneath Alaska's North Slope using spectral decomposition of 3-D seismic reflection data
AU: * Stein, J A
EM: stein@email.arizona.edu
AF: University of Arizona, 1040 E 4th St Geosciences #77, Tucson, AZ 85721,
AU: Johnson, R A
EM: johnson6@email.arizona.edu
AF: University of Arizona, 1040 E 4th St Geosciences #77, Tucson, AZ 85721,
AU: Casavant, R R
EM: casavant@email.arizona.edu
AF: University of Arizona, 1040 E 4th St Geosciences #77, Tucson, AZ 85721,
AU: Warren, M B
EM: warren@email.arizona.edu
AF: University of Arizona, 1040 E 4th St Geosciences #77, Tucson, AZ 85721,
AB: A primary difficulty for seismic interpretation of methane hydrates in regions with permafrost is that permafrost has similar acoustic properties to gas hydrate and is observed intermingling with hydrate-bearing strata in well logs and core samples. Post-stack processing of 3-D onshore seismic reflection data from the area near Milne Point, Alaska included predictive deconvolution to remove mostly short-period multiples and wavelet deconvolution to enhance frequency content; together these processes significantly enhanced data quality. However, spectral analysis of this enhanced data reveals a dominant frequency around 50 Hz and average tuning thicknesses for the survey ranging from 8-15 m, which may compromise interpretation of thin (1-8 m) hydrate intervals and small-offset faults. No direct hydrate indicators, such as polarity reversals, are evident in the data, which may be due to resolution issues. Although amplitude anomalies do not appear to directly correlate with hydrate occurrence in the data area, lateral variations in the waveform (from automated waveform analysis) appears to show a better correlation. Recent drilling, coring and logging within the survey area confirmed the existence of methane hydrate, and provided an opportunity to calibrate hydrate occurrence with the seismic response. In this analysis, in addition to conventional correlations and seismic interpretations, spectral decomposition was used to evaluate the effects of methane hydrate and permafrost zones on tuning responses at different frequencies, and provides a new tool for evaluation of methane hydrate accumulations.
DE: 8107 Continental neotectonics (8002)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting