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Field layouts  Common-offset & Zero-offset  Common-midpoint method  Up-dip and down-dip shooting  Spread types  Singlefold / Multifold recording 

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Presentation on theme: "Field layouts  Common-offset & Zero-offset  Common-midpoint method  Up-dip and down-dip shooting  Spread types  Singlefold / Multifold recording "— Presentation transcript:

1 Field layouts  Common-offset & Zero-offset  Common-midpoint method  Up-dip and down-dip shooting  Spread types  Singlefold / Multifold recording  Crooked line method  Determining field parameters

2 X Source and Receiver have always the same distance Moveout must be taken into account or corrected for Common-Offset

3 X Source and receiver are at the same location (i.e. the offset is zero -> “zero offset”) => No Move-out Zero-Offset

4 CMP = CDP CMP  CDP CMP = common mid point CDP = common depth point CMP - “ Common Mid Point”

5 + llllllll + llllllll Down-dip shooting Up-dip shooting Down-dip and Up-dip shooting Remember the refraction measurement where both shooting directions were needed to estimate the velocity of the lower layer

6 (Top view) + lllllllll single ended (end on) split spreadfan shooting single ended (inline offset) + lllllllll + llllllllllll + llllll llllll + l l l l l l l l l Common field layouts

7 + llllllllllllllllll lllllllll + lllllllll lllllllll + lllllllll active not-active active more Geophones in the Field than active channels Geometry of Geophones relative to the source remains the same roll along

8 “roll along acquisition” llllllllllllllll active not-active llllllll llllllll llllllll llllllll llllllll llllllll lllllll llllll lllll llll lll llllllll lllll llll lll ll l l l

9 Crooked line method Sources and receivers on a roadResulting line From Sheriff, 1995

10 Shot-receiver coordinate system From Reynolds, 1997

11 Midpoint-offset coordinate system X o =(X s -X r )/2X m =(X s +X r )/2 From Reynolds, 1997

12 + llll + llll + llll + llll + llll + llll + llll + llll No. geophones: 4, distance geoph: 1, distance source: 2, No. geophones: 4, distance geoph: 1, distance source: 1, Fold: 2 Fold: 1

13 l + + + + + + lllllllllll llllllllll ll llllllllllll llllllllllll llllllllllll llllllllllll

14 Number of traces per CMP Coverage (“fold”)

15 Raypaths for a given bin From Reynolds, 1997

16 Determining field parameters  Maximum offset  Depth deepest zone of interest  Minimum offset  Not greater than shallowest section of interest  Maximum array length is determined by the minimum apparent velocity of reflections  Charge size determined by ambient noise late on the record  Line orientation (up-dip, down-dip)


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