Words on processing
Pre-processing: Seismic processing is the soul of seismic as it’s the transition between seismic acquisition and interpretation Without good processing to seismic data a misleading seismic interpretation is expected to take place, according to this, a dry well might be drilled at a significant cost. The cost of selecting the accurate parameters and the optimum workflow is much cheaper than getting an unpredictable scenario during drilling We can say that the seismic processing is the eye of seismic reflection prospecting and without an optimum seismic processing the seismic becomes a blindfolded tool The aim of this processing to: • To improve the signal to noise ratio • Isolation of the wanted signals (Reflections isolated from multiples and surface waves) • To obtain a higher resolution by adapting the waveform of the signals • To obtain a realistic image by geometrical correction • To obtain information about the subsurface The energy within a seismic trace consists of - Signal: Energy which carries desired information Noise: Energy containing unwanted information The aim of signal processing is to enhance the signal and reduce noise, that is Increase Signal to Noise (S/N) Ratio where S/N ratio may be defined as energy (or amplitude) of signal/energy (or amplitude) of noise Sometimes denominator may be total energy i.e. S + N Types of Noise Random - energy which does not exhibit correlation from trace to trace - not generally source generated Coherent - predictable from trace to trace across a group of traces i.e. have a phase relationship between adjacent traces - often source generated Types of Noise - Spikes Particularly problematical White spectrum (all frequencies) Random, high amplitude, and short-lived in time Affects amplitude scaling processors severely Produces impulse response of any filter applied Noise’ (impulse response) spread to adjacent channels/traces by multi-channel processors e.g. F-K, DMO, migration (migration‘smiles’!), etc. noise attenuation techniques RANDOM • random pass filtering • Notch filtering • K-filtering e.g. trace/shot summation • F-K filtering • Stacking • Despike • F-X filtering • Coherency filtering • Editing (e.g. kill traces) Coherent • Bandpass filtering • Velocity filtering i.e. F-K filtering • Deconvolution/demultiple • Muting • Coherency filtering
by :: GeoGim
GeoGim Instructors Qualifications:
MSc. Degree or higher degrees
More than 15 years of experience for under-graduates to intermediate courses
More than 20 years of experience for intermediate to experts courses