Phase Decomposition and Its Applications

We discuss the recently introduced phase decomposition analysis, which entails amplitude variation with time for a specific seismic phase. Assuming a zero-phase wavelet embedded in the seismic data, while flat spots or unresolved water contacts may be seen on the zero-phase component, thin-bed and impedance changes will show up on phase components that are 90° out of phase with the wavelet. Similar bright spots caused by thin hydrocarbon reservoirs are associated with low impedance and show up on the phase component that is −90° out of phase with the embedded wavelet. In all cases the interpretation of bright spots is found to be convenient, and easier with the use of −90° seismic phase component. In this paper, application of phase decomposition to a few instances are first demonstrated through synthetic data examples, followed by a couple of real seismic data case studies. In particular, the case study from a gas storage reservoir in Denmark exhibits how phase decomposition can aid interpretation efforts. Some of the typical issues that seismic interpreters might come across, including the one where the input seismic data might have a phase different from zero phase are elaborated in the ‘Discussion’ section.