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Geology _ Geophysics in Oil Exploration

G drilling mud parameters tool sketches and remarks

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Unformatted text preview: ault to show fault on seismic section. Fault Polygons Horizon picking Fault segments 48 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 4-Two Way Time Map: (TWT) At first, we take the time values of horizon at each shot point Then, put these values at the line on base map. Repeat this stpe at each line. After that, Contour these values to get TWT map with suitable contour interval. NOTES: • Before contouring, First we load the fault polygons on map • The contour map must have: • Map name: (ex: Al-Dol time map) • Contour Interval: (ex: 20ms) • Scale: (ex: 1:100000) • Scale Bar: . 5km . 5-Velocity map: First, put the average velocity determined at each well. The average velocities in well became from Check-shot survey or VSP (from time/depth scale in check-shot we can determine the velocity). then, we repeat this step at each well in survey area & contouring the velocity values of wells to get Velocity map. NOTES: • The velocity required for the map is Average velocity • If there is no wells in area, we use velocity extracted from seismic data • In this case, we use the Stacking Velocity or RMS velocity. • These velocities is estimated by Velocity Analysis. • In case of determining velocity from check-shot survey, the result velocity will multiplying by 2 (to convert it to oneway time). • Ex: if the time is 1980ms & depth is 8000ft, so the velocity will equal 49 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 6-Depth contour map: We extract the depth map values from the velocity & one way time map. The depth converted map shows the depths of intersted horizon. we usually prefer to drill at the higher areas (which called hot areas) . NOTES: • At most cases, the shape of two way time map is look like the Depth map • If there is a closure occurred in TWT map & not existed in Depth map, the error usually come from the velocity map then try to fix it. • If there is a closure occurred in De...
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