Seismic processing

The purpose of seismic processing is to manipulate acquired data into an image or set of images of the subsurface geology. Processing consists of applying a sequence of routines on a computer guided by a geophysical processor. There is no single correct processing sequence for a given data. Many stages throughout processing require judgements and decisions to be made which are often subjective, and rely on the processors experience or bias. It is wise that an interpreter should be involved at all stages to check that processing decision do not radically alter the interpretability of the result in a detrimental manner.

A further article many be useful for guidelines for specific processing problems encountered in various geologic provinces.

Contractors
Most commercial seismic data processing is carried out by contractors who are able to perform most jobs quickly and cheaply with specialized staff, software, and hardware. The following is a not-exhaustive list of geophysical contractors who specialize in seismic data processing

Processing flow
A processing flow is a collection of processing routines strung together and applied to a data volume. Most processing routines accept input data, apply a process to it and produce output which is saved before passing it to the next processing stage. Several of the stages are strongly interdependent and each of the processing routines will require several parameters to be chosen or defaulted. Some parameters will be defined, for instance, by the acquisition geometry and some must be determined for the particular data being process by the process of testing. Parameter choices are almost always subjective, but a good rule of thumb is to keep things as simple as possible unless there is a reason suggesting otherwise.

A simple example of a land processing flow
List of operations, more or less the order in which they could be applied. Not all of them are necessary.

Demultiplex

Geometry labeling

True amplitude recovery (e.g. T1.5)

Filter (minimum phase equivalent of sweep)

Surface consistent scaling

Refraction statics applied to a floating datum

Surface consistent scaling

Velocity analysis (a second round)

Surface consistent residual statics (a second round)

Scaling

NMO correction

Stretch mute

Time and spatially varying mute

Non-surface consistent statics

DMO velocity analysis

DMO correction

Stack

Post-stack time migration

Bandpass filtering

F-XY deconvolution

Output: Post-stack time migration volume

Prestack processing flows
Isotropic assumption

AVO processing flows
Isotropic assumption

VTI and TTI processing flows
Thomsen's parameters

HTI AVAZ processing flows
Azimuthally sorted gathers have sinusoidal perturbations about an average RMS velocity. The sinusoid represents the magnitude of the travel time variation between the fast and slow orientation 'above' the reflection event. The phase of the sinusoid can be used to extract the orientation, and the amplitude can be used to determine the ellipticity or eccentricity of the seismic HTI anisotropy.