 |
| Titel |
3-D seismic modelling in the Flin Flon mining camp, Canada |
| VerfasserIn |
Michał Malinowski, Don White, Ernst Schetselaar |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047292
|
|
|
|
|
|
| Zusammenfassung |
| A comprehensive seismic survey for VMS ore exploration was recently conducted in the Flin
Flon mining camp (Trans-Hudson Orogen, Canada). The seismic project comprised a total of
75 km of high-resolution 2-D profiles and a 14 km2 3-D survey. Processing of the
vertical-component data for P-wave reflections reveals prominent reflectivity associated with
contacts between the metasedimentary and mafic volcanic rocks, as well as moderately
dipping reflectivity within the polydeformed volcanic rocks including the main rhyolite
horizon which hosts the VMS deposits. However, complex volcanic stratigraphy of the Flin
Flon mining camp makes the interpretation of the 3-D seismic data especially challenging.
Toward providing further constraints on the interpretation of seismic data, we have performed
3-D seismic forward modelling on a detailed geological model constructed for the camp,
both in stack and prestack (i.e,. simulating the complete 3-D survey) mode. A 3-D
geological model of the Flin Flon mining camp was created based on an extensive
set of drillholes, surface geology, interpretation of the 2-D seismic profiles and
predictive modelling. The original model was generalized into six lithofacies and the
elastic rock properties were assigned based on the rock property measurements
on core samples. 3-D forward seismic modelling implemented the phase-screen
method, which allows the calculation of an approximate (narrow angle) but fast
solution to the elastic wave equation in complex 3-D media. To simulate the 3D
stack volume, initial simulations were conducted by using the “exploding reflector”
mode (plane-wave simulation) both for the whole model and for the ore lenses
only. Ultimately, the prestack data simulations were performed, by calculating the
individual shot-gathers using the real survey 3-D geometry. A total number of 934 shot
points were simulated, each recording 23 lines. Data were binned using the same bin
parameters as the original 3-D survey (25 m inline bin size and 12.5 m crossline
bin size) and processed in a similar manner up to DMO and post-stack migration
phase.
Comparison of the “exploding reflector” simulation performed for the original model and
for the ore bodies only with the processed 3-D DMO volume suggests that the lack of a clear
ore body response in the real data (namely the diffraction patterns) can be mainly attributed to
the wave interference arising from the complex volcanic stratigraphy. Alternatively, it could
be due to the fact that the most of the ore lenses included in the 3-D model have been already
mined out. However, the mined out ore was back-filled with material that should still
produce a significant acoustic impedance contrast with the host rock. In fact, a close
examination of the results of modelling and the real data suggests that the bright dipping
reflectors in the 3-D DMO volume correspond to the down-dip diffracted energy of the
ore bodies. As our model includes the known ore bodies, we can use predicted
seismic data in combination with the 3-D seismic survey for direct ore targeting. |
|
|
|
|
|
|