AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Gas Detection by Spectral Decomposition Using Matching Pursuit
(1) EXPRC ARC, Saudi Aramco, Dhahran, Saudi Arabia.
(2) EXPEC ARC, Saudi Aramco, Dhahran, Saudi Arabia.
Traditional methods for detecting fluid response are based on the pure elastic Gassman theory which assumes the resultant seismic effects are frequency-independent. Recently, there have been investigations into the use of spectral decomposition for extracting information on fluid properties. Researchers have discussed how to calculate the frequency-dependent seismic reflection response, and the resultant frequency-related properties, such as attenuation and dispersion characteristics. To derive frequency-related attributes from seismic data, it is more convenient to use spectral decomposition techniques. A seismogram can be decomposed into constituent wavelets, and a time versus frequency analysis can readily be constructed by weighted superposition of wavelet spectra as a function of record time. The spectral decomposition using Morlet wavelets by matching pursuit requires no windowing and no use of the Fourier transform. This method has excellent time resolution and eliminates “Gibbs phenomena” as well as other undesirable effects windowing.
We have developed an accurate Morlet wavelet spectral decomposition using matching pursuit. This allows us to calculate a range of frequency-dependent attributes, such as, absorption coefficients and amplitude gradients in the frequency domain. We have observed that the frequency response of a seismic reflection and its resultant attenuation and dispersion may have a link to fluid saturation. We have applied the method on real data from Saudi Arabia to demonstrate this correlation. The results suggest that careful data processing and modeling are necessary to understand the complex effect of different fluids on the spectral response for reliable interpretation.