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PROCESSING & IMAGING
Reverse Time MigrationTTI Two-Way Wave-Equation Imaging
Kirchhoff Migration.
Reverse Time Migration. This example shows reprocessing and RTM
providing better imaging of the pre-salt data.
FEATURES:
Imaging of all possible arrivals
Superior multi-path imaging
No dip limitation
Accounts for extreme lateral velocity var iations
Wide-azimuth and TTI capable
TTI RTM used extensively in Gulf of Mexico subsalt
exploration, and in other areas worldwide
Reverse Time Migration provides superior imaging for complex
structural plays. By using a fulltwo-way solution to the wave
equation it is able to construct images using all possible
arrivals,
and to handle extreme lateral velocity variations without
imposing any dip limitations. Reverse
Time Migration is therefore able to make use of energy that
would otherwise be discarded or
seen as noise by other imaging methods. The technique is
particularly suited to areas where
direct illumination of the subsurface is limited. Incorporation
of Tilted Transverse Isotropy (TTI) in
the algorithm provides further improvements in image
quality.
BENEFITS:
Improved imaging of complex plays
Steep dips
Complex overburdens, regardless of dip or rugosity
More accurate focusing, positioning and amplitudes
in complex areas
Inclusion of TTI produces high-fidelity velocity models
Tupi Discovery
Tupi Discovery
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PROCESSING & IMAGING
10
FPI-430-V1
REVERSE TIME MIGRATION
Conventional wave-equation migration is per formed by
propagating data
downward through a velocity model into the earth and is limited
wherethe structure and velocity eld generate more complex arrival
s, such
as turning and prism waves. Complex propagation paths give r ise
to
arrivals that are seen as noise in the imaged data.
Reverse Time Migration propagates events both downward and
upward
through the earth model, explicitly handling turning waves and
all other
complex propagation paths. In many cases, the ability to make
use of
these complex wave modes allows imaging of parts of the
subsurface
that otherwise have poor direct illumination.
TTI ANISOTROPY
Wide-azimuth (WAZ) data acquisition allows more reliable and
accurateTTI anisotropic parameters to be derived that enhance image
quality.
Inclusion of these anisotropic effects in the RTM algorithm has
greatly
improved the imaging of complex structures. TTI RTM reliably
produces
better subsalt images and more accurate depths f rom WAZ data
than
those from either isotropic or VTI RTM. CGGVeritas routinely
uses TTI RTM
for production imaging.
Isotropic RTM of a traver se line near the Jack discove ry in
the Gulf of Mexico.
Anisotropic TTI RTM of a traverse line near the Jack discovery.
T TI RTM produces more
continuous subsalt images than isotropic RTM does.
VTI RTM of a traverse line near West Tonga discovery in the Gulf
of Mexico.
TTI RTM of a traverse line near West Tonga discovery. Subsalt
images are more coherent and
focused on TTI RTM results than those from VTI RTM.
