Print this pageBLAKE, 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