Changes

==3-D versus 2-D migration==

==3-D versus 2-D migration==

[[file:three-dimensional-seismic-method_fig2.png|thumb|{{figure number|2}}(a) Selected time slices. Copyright: a marine 3-D survey and (b) a time-structure map of a marker horizon derived from the 3-D volume of migrated data. (Data courtesy of Western Geophysical, Division of Western-Atlas International.]]

[[file:three-dimensional-seismic-method_fig2.png|300px|thumb|{{figure number|2}}(a) Selected time slices. Copyright: a marine 3-D survey and (b) a time-structure map of a marker horizon derived from the 3-D volume of migrated data. (Data courtesy of Western Geophysical, Division of Western-Atlas International.]]

Three-dimensional migration often produces surprisingly different sections from 2-D migrated sections (see [[Seismic migration]]). The example in [[:file:three-dimensional-seismic-method_fig1.png|Figure 1]] shows a no reflection zone on the 2-D migrated section, while the same zone contains a series of continuous reflections on the 3-D migrated section that are easily correlated with reflections outside that zone. When we do 2-D migration, we confine the movement of the energy into the plane of the line itself. So the energy contained in the unmigrated stacked section in Figure 1a is indeed the same as the energy contained in the 2-D migrated section in [[:file:three-dimensional-seismic-method_fig1.png|Figure 1b]], except that it has been moved somewhere else on the section. As a result of moving the energy during 3-D migration within the 3-D volume, some energy moved into the section ([[:file:three-dimensional-seismic-method_fig1.png|Figure 1c]]) from others and some moved out of the section and migrated into the others.

Three-dimensional migration often produces surprisingly different sections from 2-D migrated sections (see [[Seismic migration]]). The example in [[:file:three-dimensional-seismic-method_fig1.png|Figure 1]] shows a no reflection zone on the 2-D migrated section, while the same zone contains a series of continuous reflections on the 3-D migrated section that are easily correlated with reflections outside that zone. When we do 2-D migration, we confine the movement of the energy into the plane of the line itself. So the energy contained in the unmigrated stacked section in Figure 1a is indeed the same as the energy contained in the 2-D migrated section in [[:file:three-dimensional-seismic-method_fig1.png|Figure 1b]], except that it has been moved somewhere else on the section. As a result of moving the energy during 3-D migration within the 3-D volume, some energy moved into the section ([[:file:three-dimensional-seismic-method_fig1.png|Figure 1c]]) from others and some moved out of the section and migrated into the others.