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Unformatted text preview: eismic processing in which reflections in seismic data are moved to their correct locations in space, including position relative to shot points, in areas where there are significant and rapid lateral or vertical changes in velocity that distort the time image. This requires an accurate knowledge of vertical and horizontal seismic velocity variations. • Pre Stack Depth Migration: if the migration process occurred before stacking • Post Stack Depth Migration: if the migration occurred after stacking Before Migration After Migration 43 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Post Stack Processing: Sometimes, we have a seismic section & already had been processed in past but we need to enhance & filtering this data again. Usually, this data came in seismic section papers (not in tapes), So at first we scan this data & convert it to SEG-Y format by Victorization process. Sometimes also, we digitize the shot point maps & put X-Y directions in the SEG-Y trace header. Post Stack Processing steps: • • • • • 44 Geology & Geophysics in Oil Exploration Mahmoud Sroor Resampling: convert the trace into digital form (or from 2ms to 2ms for example). Interpolation: is to estimate a synthetic trace between two traces. AGC & Trace Balance: is automatic gain control is used to build up weak signals. Trace Mix: control the gain like AGC but laterally (from trace to other). Migration: apllies both Prestack Migration & Poststack Migration. Geology & Geophysics in Oil Exploration Ch7: Seismic Data Interpretation Seismic interpretation & subsurface mapping are key skills that are used commonly in the oil industry. It is used to generate reasonable models and predictions about the properties and structures of the subsurface. To start interpretation, We must have: • • • • • • Base Map: shot point location Seismic sections: Inline & Crossline Available Wells: Velocity data from wells:from Cheak...
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- Spring '10