Thursday, November 20, 2014

Static Corrections

Static corrections are probably the most critical processing step for land data. They are especially important in areas of rough terrain and where the near-surface velocity is highly variable-either laterally or horizontally. This near surface velocity affects reflection continuity, resolution, the accuracy of velocity analysis, and structrual form.

Usually before land data is analyzed for NMO velocities and stacked, corrections have to be made to account for anomalous effects caused by significant elevation or near-surface velocity changes caused by the water table, by alluival and by weathering.

Poor static corrections result in poor reflector continuity and poor velocity control. Accurate static corrections can make the difference betwen an outstanding section and one that is not usable. Static corrections are a processing problem over which the interpreter has little control, other than to request reprocessing.

However, there are some pitfalls in static corrections that can, in some circumstances, produce good-looking but structurally incorrect sections, and as a rule of thumb, beware of reflections that bear a relationship to the surface shape.

Static corrections for marine data involve correcting for the depth of source and hydrophones below the sea-level datum (theoretical mean sea level). However, if incorrect they can cause considerable problems for ties of well to seismic and in tying data from surveys with different static corrections

Reference : Badley, E. Michael. Practical Seismic Interpretation.

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