Frequency Extension of Signal
Frequency Extension of Signal utilizes the low-frequency components of seismic data, which normally have a higher S/N ratio than the high-frequency components, to enhance, extend and/or replace the high-frequency components.
FES is a multi-faceted technology that can be parameterized to
- increase event continuity by stabilizing reflection character,
- sharpen fault and channel patterns by enhancing internal geometries,
- better define bed terminations and formation truncations,
- replace high-frequency removed in internal multiple-suppression, and
- reveal hidden stratigraphic and structural geometries.
In FES, Morlet wavelets provide the spectral transformation of a PSTM trace into amplitude and phase traces (time-frequency domain). Pre-FES, the signal-to-noise ratio is measured and suppressed in the time-frequency domain. With the signal defined in the low-frequency components, the fundamental frequency components and their single or multiple harmonics are weighted and summed based on S/N for predicting the high-frequency components. Depending on how the harmonics are weighted, FES can be designed to increase the wavelet character by removing phase distortions in the high-frequency components (first figure below); or designed to increase the bandwidth and stratigraphic and fault patterns (second figure below); or to provide a mix of both characteristics.