L7d data files

Raw Data The full dataset is as big as 45Gb, avaible on DLT tapes.

Common-azimuth Data To be done.

Velocity Model Locateed at /data_3d/elf_north_sea/L7d-vel.H
Velocity model created by Elf & IFP (Project ``Helios'') using the so-called ``SMART'' method (Sequential Migration Aided Reflection Tomography). The structure of the salt dome is highly 3-D, with serious illumination problems under its edges (Figure 1).

Stack Located at /data_3d/elf_north_sea/L7d-near-nmo-stack-fine.H
Near-offset (0-1000m) NMO-stack

Zero-offset Migration Located at /data_3d/elf_north_sea/comaz_zo_salt_fine.h

Prestack 2-D line

Usage none (yet).

Geometry Acquisition: 2 sources, x streamers (most likely 3).
In3d:
---------------------------------
********** L7d_all.H ************
4 -esize Synched data_format-xdr_float
---------------------------------
n1=1500 o1=0.000000 d1=0.004000 label1=time
n2=7411523 o2=1.000000 d2=1.000000 label2=trace number
Data: in=/scrsa3/louis/Elf/Data/L7d_all.H@
7411523 elements, 44469138000 bytes in data file
---------------------------------

Attr3dhead:

key min max mean nzero rms norm

cdp 2900.0000 3900.0000 3389.9319 7411523 3400.5400 9257668.44

offset 186.0000 3571.0000 1764.1710 7411523 1989.4291 5416044.20

ncdp_s 2773.4941 3926.8994 3438.5354 7411523 3449.2773 9390351.31

nligne_s 1346.6554 1520.4437 1428.9248 7411523 1429.5942 3891943.38

ncdp_g 2772.9077 4026.9609 3341.0813 7411523 3352.4868 9126847.67

nligne_g 1347.1848 1528.9202 1429.6726 7411523 1430.3911 3894112.88

s_x -1686.7405 13691.9580 7180.4541 7411523 8044.3945 21900150.11

s_y 1416.3849 5761.0933 3473.1201 7411523 3641.2247 9912910.97

g_x -1694.5596 15026.1074 5881.0698 7411522 6939.6676 18892629.00

g_y 1429.6204 5973.0039 3491.8162 7411523 3671.1157 9994286.74

nline 1354.4266 1515.5315 1429.2987 7411523 1429.9876 3893014.44

aoffset 185.6369 3571.9861 1764.5095 7411523 1989.8103 5417081.89

azimuth -1.2745 1.5323 -0.0261 7411431 0.1345 366.08

cmp_x -8.3235 13338.0527 6530.7617 7411522 7446.8040 20273262.93

cmp_y 1610.6659 5638.2871 3482.4683 7411523 3654.9572 9950296.70

offset_x -3463.4939 3383.3154 -1299.3843 7411523 1980.6512 5392147.21

offset_y -990.2041 786.0776 18.6959 7411431 190.6978 519157.71

Problem Multipathing - Illumination problems / Shadow zones - Common-angle gathers

History of Data Dataset given to SEP in 1998, originaly for testing AMO and common-azimuth migration. The contact at Elf Exploration Production is Henri Calandra.

Preprocessing A correction of amplitude has been applied: geometrical spreading

$$A(t) = \left( \frac{t}{250} \right)^{+1.8}$$

Also, the multiples due to sea bottom have already been removed.
Proprietary Considerations The L7d data are free to be used by SEP only, including publications in articles or SEP reports with the usual acknowledgements to Elf Aquitaine.

 

vel-model
Figure 1 Elf ``SMART'' velocity model

 

nmo-stack
Figure 2 NMO-stack of the near offsets (0-1000m)

 

zo-mig
Figure 3 Zero-offset migration of the near offsets (0-1000m)

 

2D-line-nmo-stack
Figure 4 NMO-stack of the near offsets (0-1000m), section corresponding to the 2-D synthetic data

 

2D-line-zo-mig
Figure 5 Zero-offset migration of the near offsets (0-1000m), section corresponding to the 2-D synthetic data