1) EXAMINE SEISMIC DATA
Description of the data set
Two dimensional (2D) land acquisition line from east Texas, USA were used to illustrate the processing codes. Some of the important parameters are:-
- Number of shots = 18
- Number of traces in line = 594
- Receiver interval = 220ft
- Time sampling interval = 2ms
- 8-64Hz band pass filter has been applied to the data in the field
2) QUALITY CONTROL
Pre-processing of Seismic Data
QC steps are necessary to carry the remaining seismic data forward and to obtain accurate image of subsurface structures. The QC process involves:-
- De-multiplexing
- Reformatting
- Setup of field geometry
- Trace editing
- Gain application
- Statics application
3) NOISE ATTENUATION
Seismic Signal & Noise
Objective of seismic data processing: to improve as much as possible the signal to noise ratio (SNR). Poor seismic records usually have less than one SNR.coherent energy = signal of interest, correlated, energy generally concentrated in a fairly narrow band
incoherent energy = noise, uncorrelated, broad band.
4) DECONVOLUTION
Spiking Deconvolution
Seismic data is smoothed after frequency filtering hence its vertical resolution is affected due to loss of some of its original wider frequency band. Aims of seismic deconvolution is to increase the vertical resolution of the data by compressing the source wavelet to a zero phase spike known as spiking deconvolution.
5) SORTING, VELOCITY ANALYSIS, STACKING
Revealing true image of subsurface
This requires compressing the seismic data to infer a first approximation for subsurface image and may include:-
- sorting the shot gather to CMP data
- picking stacking velocities and applying NMO correction
- stacking all CMP's
6) STATIC CORRECTION
Compensate various effects on the data
Effects such as those related to near surface, variations in elevations, weathering and reference to a datum. Aim of applying static corrections to seismic data is to determine the reflection time, assuming the existence of a flat surface plane with no weathering layer. The corrections are:-
- elevation static corrections
- residual static corrections
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