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Subsurface Model

To illustrate the method, I created a simplified subsurface model corresponding to a target horizon whose depth changes from about 0.3 km to about 2 km. The model simulates a land prospect, has high local dips and mild topography. Figures [*] and [*] show views of the model from the inline and the cross-line direction respectively. The model has significant dips in both directions. Similarly, Figures [*] and [*] show views of the target horizon from the inline and the cross-line direction. There are two possible reservoirs in this horizon, one at the top and one in the small structure to the right (Figure [*]). The model is 10 km x 10 km with a maximum depth of about 3 km. The velocity field consists of blocks delimited by the reflectors. Within each block the velocity changes laterally as well as vertically in a gradient-based fashion as summarized on Table 1. Velocity at each point of each block is computed as $v(x,y,x)=v_0+x\frac{\Delta v}{\Delta x}+y\frac{\Delta v}{\Delta y}+z\frac{\Delta v}{\Delta z}$.

 
model1
model1
Figure 1
Subsurface model. View from the strike direction. The horizontal dimensions are 10 km x 10 km. The depth of the deepest reflector is 3 km.
view

 
model2
model2
Figure 2
Subsurface model. View from the dip direction. The horizontal dimensions are 10 km x10 km. The depth of the deepest reflector is 3 km.
view

 
target1
Figure 3
Target reflector. View from the dip direction. The reservoir corresponds to the top of the structure at a depth of about 0.3 km.
target1
view

 
target2
Figure 4
Target reflector. View from the strike direction. The reservoir corresponds to the top of the structure at a depth of about 0.3 km.
target2
view


 
Table: Velocity information. Each block is delimited by two reflectors, numbered as indicated on Figure [*]. Units are m/s.
Block Reflectors v0 $\frac{\Delta v}{\Delta x}$ $\frac{\Delta v}{\Delta y}$ $\frac{\Delta v}{\Delta z}$
1 1 and 2 2000 0.01 0.05 0.5
2 2 and 3 3000 0.05 0.01 0.2
3 3 and 4 2400 0.01 0.01 0.5
4 4 and 5 3600 0.05 0.01 0.1
5 5 and 6 5000 0.0 0.0 0.0


next up previous print clean
Next: Standard 3-D Survey Design Up: Alvarez: 3-D survey design Previous: Introduction
Stanford Exploration Project
7/8/2003