BLAKE, BRUCE A., and DANIEL FIGUEROA
YPF/Maxus, Dallas, TX
Abstract: Strike
Line Methodology
in Areas of Complex Geology
Exploration in areas of complex geologic structures,
such as the fold and thrust belt play of the southern Sub-Andean region
of Bolivia, presents special problems in seismic data acquisition and interpretation.
Several criteria are used in locating new seismic lines which relate directly
to surface geology (i.e., topographic highs, age order of outcropping rocks,
surface dips). These data alone are not sufficient to ensure the location
of a prospect in the subsurface. We believe that a twostaged exploration
effort of first shooting
strike
lines followed by well-positioned
dip
lines
is a more cost-effective method.
We advocate first shooting
strike
lines (e.g.,
parallel to the outcropping formations) along the back limbs of thrust
structures; later recording
dip
lines over culminations seen on the
strike
lines. The back limb
strike
lines are less expensive to shoot than either
strike
lines on the crests of the mountain ranges or
dip
lines that cross
the mountains. Three dimensional seismic modeling shows that the subsurface
position of the back limb
strike
lines is about the same as for the crestal
strike
lines. Data quality is better in the back limb
strike
over the crestal
line mainly because the topography is flatter and the surface geology is
Tertiary age. Data quality on the back limb
strike
line is better than
dip
line data mainly because the reflections are flatter and the ray paths
less complex. Fore limb
strike
lines can be as useful as back limb lines
in this type of exploration play.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas