Sismica

Seismic Data Processing and Interpretation
1. Introduction The purpose of seismic processing is to manipulate the acquired data into an image that can be used to infer the sub-surface structure. Only minimal processing would be required if we had a perfect acquisition system. Processing consists of the application of a series of computer routines to the acquired data guided by the hand of the processing geophysicist. The interpreter should be involved at all stages to check that processing decisions do not radically alter the interpretability of the results in a detrimental manner. Processing routines generally fall into one of the following categories: * enhancing signal at the expense of noise * providing velocity information * collapsing diffractions and placing dipping events in their true subsurface locations (migration) * increasing resolution.

2. Processing Steps There are number of steps involved from seismic data acquisition to interpretation of subsurface structure. Some of the common steps are summarized below: Static Correction Velocity Analysis NMO/DMO Stacking Migration (Time/Depth, Kirchhof’s, f-k domain ) Interpretation Seismic data to subsurface geology

Acquisition Processing

In order to work with above steps (or to work more with seismic data), a number of signal processing operations are needed to accomplish the job. Some of them are: i) Sampling data, ii) Mute, iii) Amplitude recovery/ corrections, iv) Filtering, v) Deconvolution, v) f-k analysis etc. Some signal processing tools are explained in section three.

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2.1 Data acquisition Shot gather:

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Multiple shotpoints: If more than one shot location is used, reflections arising from the same point on the interface will be detected at different geophones. The common point of reflection is known as the common midpoint (CMP).

CMP:

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CMP gather: The CMP gather lies in the heart of seismic processing for two main reasons: i) the variation of travel time with offset,