ADDY, SUNIT K.
CGG Americas
Inc., Houston, TX
Abstract: Neural Net Generated Classification
and Near Reflectors Geometry Maps in Seismic
Stratigraphic Interpretation
Seismic
stratigraphic analysis involves
picking of. reflection terminations, such as onlaps, downlaps, toplaps,
truncations etc. and lateral mapping of these events. This process is very
slow even if the interpreter picks them only on a limited inlines or cross
lines in a 3D data set and not on all lines. New technologies for mapping
lateral extensions of such reflection terminations based on every line
will be presented here using two independent methods. These techniques
are a) neural net classification of
seismic
traces b) near reflectors geometry
(NRG
attribute
) mapping above or below a mapped horizon (licensed and patented
from Elf Aquitaine). Both techniques complement each other and can be done
in a very short time.
In a neural net generated classification map the
distribution of similarly shaped seismic
wiggle traces in an interval parallel
to a horizon is shown. This map can be interpreted to observe lateral extensions
by calibrating it with a limited number of termination pickings. Similarly,
NRG
attribute
mapping in which the distance between the mapped horizon
(unconformity) and peak (or trough) above (or below) the horizon is measured
directly shows onlap, downlap or truncation. Our reflection termination
maps show greater details than manual conventional termination maps.
Using these techniques, hydrocarbon producing Lower Wilcox sand rich horizons of Eocene age onlapping. on the Lavaca canyon wall in south central Texas were mapped in two 3D surveys resulting in additional exploration targets. Reservoir facies analysis was also done from these maps. In another 3D survey in the North Sea, the truncation of Upper Jurassic hydrocarbon bearing sands beneath the Base Cretaceous unconformity shows the extent of the field suggesting that such techniques can be used as quick exploration tools.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas