Time Frequency Spectral Decomposition for Determination of Bottom Simulating Reflector of Gas Hydrate Seismic Data

Abstract

Gas hydrate, a complex compound, formed in the special condition of low temperature and high pressure, has been considered as very high potential new energy resources. In the gas hydrate exploration, bottom simulating reflector (BSR), defined as the boundary between gashydrate and free gas zone, is considered as the most important indicator for the gas hydrate exploration by seismic reflectivity method. Additionally, the location of BSR can help to estimate the thermo-dynamic parameters for gas hydrate stability zone. Spectral decomposition methods such as STFT (Short Time Fourier Transform), CWT (Continuous Wavelet Transform) and MPD (Marching Pursuit Decomposition) for seismic data has been proposed and applied in the various rock reservoirs to characterize hydrocarbon indicators as positive anomalies in the spectrum. Because the BSR has several specific characteristics that create strong reflectivity pattern in the seismic section, the time-frequency decomposition could be used to distinguish this boundary in the gas hydrate seismic data by taking the high energy position at the frequency gather slice. The output of seismic data processing for gas hydrate exploration in the Ulleung basin, Korea, will be used for time-frequency analysis and integrated to the well logging data in order to locate the BSR in seismic data. These results showed the high energy position at the time of 0.25-0.30 second below the sea floor reflector at the frequency gather slice of 60 Hz that would indicate to the position of BSR