Geology _ Geophysics in Oil Exploration

In case of determining velocity from check shot

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Unformatted text preview: Shot, VSP. Formation Top of the well: to determine the top of horizon Logs & reports: Sonic,GR,Density & other logs Before starting the interpretation steps, first we will define some definations & processes related to seismic interpretation . Check Shot survey: A type of borehole seismic data designed to measure the seismic traveltime from the surface to a known depth. P-wave velocity of the formations encountered in a wellbore can be measured directly by lowering a geophone to each formation of interest, sending out a source of energy from the surface of the Earth, and recording the resultant signal. From this survey, we will have velocity & depth, we estimate the time & plot result in Time/Depth Scale. At this case, the reading will be taken at every 100ft. Vertical Seismic Profiling (VSP): A class of borehole seismic measurements used for correlation with surface seismic data, for obtaining images of higher resolution than surface seismic images and for looking ahead of the drill bit; also called a VSP. Purely defined, VSP refers to measurements made in a vertical wellbore using geophones inside the wellbore and a source at the surface near the well. Most VSPs use a surface seismic source, which is commonly a vibrator on land and an air gun in offshore or marine environments. Recording at any level will contain both upgoing & downgoing waves. Both upgoing & downgoing waves will be associated with multiples due to reflection both above & below the geophone. VSP data is also has its processing which called VSP processing. Another advantage for VSP is the ability to give good results in deviated wells, where synthetic Seismiogram are often unrealiable. VSP produces Time/Depth Scale & VSP image, where Check-shot just produces time/depth scale 45 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration VSP has higher resolution than Check-shot survey ( reading every 10ft) The total waves recorded at detect...
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