Sensitivity of seismic well ties to attenuation effects
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Seismic attenuation affects seismic data by reducing the amplitudes, by imposing phase distortion and by decreasing the data bandwidth. These effects need to be adequately managed to obtain satisfactory well ties. In this study two experiments were performed to assess the detectability of phase Q effects on seismic well ties. The effects were to be quantitatively determined by studying the wavelets extracted from well ties. The first experiment was carried out to study the attenuation effects on synthetic data, to establish whether the software was adequate for wavelet extractions, and to obtain a set of parameters with which to perform wavelet extractions. The second experiment was then performed to assess the detectability of phase Q effects using data from a real seismic survey. Wavelets were extracted from two seismic well tie windows to check the stability of the wavelets with time. The synthetic experiment successfully extracted wavelets and was deemed suitable for wavelet extractions. Attenuation effects were evident from the wavelets. The wavelets estimated from the second experiment also showed the effects of Q. Both experiments implied that the outcome of imposing a time shift on a wavelet was equivalent to a wavelet of the same shape estimated using a different reference frequency for Q modeling.