A Review of Pre-Stack Depth
Migration
(PreSDM) Process Flow Development in the Gulf of Mexico
By
Jock M. Drummond1, David Walraven1
(1) Anadarko Petroleum Corporation, The Woodlands, TX
The past decade has been a period during which rapid advances have taken
place in the application of imaging technology and in particular in Pre-Stack
Depth Migration
(PreSDM). Improvements in the application of PreSDM have been
brought about by the need in the industry to resolve increasingly more difficult
imaging problems, to understand the fundamentals of complex regional geology, to
provide a cost effective PreSDM solution and ultimately to continually strive
for the most accurate geological model.
PreSDM can be considered the ultimate link between Geophysics and Geology. In
order to obtain the most accurate depth image the pre-stack seismic data must be
imaged with a velocity
model that is based on the geology and derived through
the seismic data. Generating the full
velocity
model is an iterative process
requiring close interaction between seismic processing geophysicists,
interpretive geophysicists and regional or structural geologists. PreSDM the
ultimate link, is also a catalyst to improved communication between
geoscientists in the exploration and development teams.
In the past two years new approaches to PreSDM, other than Kirchhoff, have
been implemented. These include for example full wavefield acoustic based shot
domain wave equation migration
(WEM), plane wave imaging solutions, and grid
based tomographic solutions to
velocity
model building. As well as the inherent
advantages of WEM new challenges are also introduced for the
processing/interpretation teams. Through massive clusters, recent NEC Earth
Simulator has 35,600 Gigaflop capability, PreSDM products include WEM image
results both in stack and gather mode,
velocity
and geological models, and
illumination models.
In future Geoscientists will use all of these products and more in a fully integrated environment to enhance their understanding of the geology and to reduce cycle time. Other challenges, including for example anisotropic model building and WEM elastic solutions, in PreSDM remain to be solved in a regular commercial basis.