Improved Imaging of the Darby Thrust Fault using
Multi-Component Seismic Receivers
Shuki Ronen,
VeritasDGC, 10300
Town Park Drive, Houston, TX 77071,
phone: 832-351-8554, [email protected], Mark Wagaman,
Veritas, Denver, CO, and Chris Ansorger,
Veritas, Calgary,
AB.
Seismic imaging in rough terrain where Paleozoic rocks are thrusted to the surface over Cretaceous sediments,
can be a challenge using conventional methods. Advances in acquisition
technology include multi-component (3C) receivers. Conventional single-
component (1C) systems consist of coiled geophones which record only the
vertical component of the seismic wavefield whereas
new 3C digital sensors utilize Micro-Electro-Mechanical Systems accelerometers
to record all three components of the full wavefield.
To evaluate the applicability of such new 3C sensors in rough terrain we
conducted a test over the Darby thrust fault in southwest Wyoming. Over the thrust, near the center of
the line, the elevation varied 200m vertically over a horizontal distance of
400m. The source was 5kg Pentolite at 18m hole depth, with 50m shot interval. The wavefield
was recorded by both 12-element linear and 36-element areal
geophone group arrays at 50m interval as well as by 3C sensors at 25m interval.
The processing sequence included tomographic
refraction statics, coherent and random noise
attenuation, surface consistent deconvolution,
two iterations of velocity analysis and residual statics,
and pre-stack migration. We applied polarization filters to the 3C data to
separate signal and noise. No such polarization filtering is possible with any
1C data. All types of receivers provided good data away from the more complex, thrusted area. However, the 3C sensors provided much better
resolution and imaging of the complex structure of the Darby thrust. We thank
Marvin Johnson and Vinny Buffenmeyer
of ExxonMobil for initiating, funding, designing, and
supervising the data acquisition.