Geology _ Geophysics in Oil Exploration

At this step we gather these cdp traces then

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Unformatted text preview: ed dip Spread: source is deviated by small distance perpendicular to the line • Gapped dip Spread: geophone groups near the source is turned off B‐End on Spread: the source is at one end of geophone groups C‐Broad side Spread: source has offset 500‐1000m perpendicular to seismic line • T‐Broad side spread: source is opposite the line center • L‐Broad side spread: source is opposite one end of the line Some definitions: • • • • • • • • Geophone Station: no. of geophones related to one recording unit. No. of channels: no. of geophone stations. Geophone interval: is distance between geophone stations. Shot point interval: is distance between shots (if more than one shot). Line number: is specific name for line of survey. File No.: The number of file or shot for this line. Reel No. =Tape No.: number of tape for certain line (if line is recorded at more than one file). Record No.: number of shot within one reel (if the reel contains more than one shot). 3‐D marine 2‐D marine 37 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Ch6: Seismic Data Processing Alteration of seismic data to suppress noise, enhance signal and migrate seismic events to the appropriate location in space. Processing steps typically include analysis of velocities and frequencies, static corrections, Deconvolution, normal moveout, dip moveout, stacking, and migration, which can be performed before or after stacking. Seismic processing facilitates better interpretation because subsurface structures and reflection geometries are more apparent. Multiplex & Demultiplex: Signals from all receivers arrive at the recorder at the same time. However recorder is only capable of measuring one receiver at the same time, so we use the Multiplex technique. Multiplexer: rotary switch rotates every few Millie seconds to sample each trace. Multiplex cycle: one turn of the switch. Sample rate: is time taken to complete one multiplex cycle (generally 2 or 4 ms). To collect all of thes...
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