Print this pageSeismic Indications of Deep-Seated Faults and Their Impact on Trapping System
Agounizera, S.,
The presence of thick Triassic and Jurassic evaporites
influences seismic data quality of Cambrian horizons in the region between the
giant Hassi-Messaoud oil field and the Dorban trough and poses an important problem for prospect
evaluation. It is difficult to extrapolate folds and faults in the post salt
section down to the prospective Paleozoic section and weak reflectivity within
the Cambrian clastic section makes it difficult to
pick horizons and faults independently. In the past, Paleozoic structure maps
have been constructed by adding isopachs to the
Mesozoic horizons. We think that this approach is the primary reason for
drilling dry holes on invalid Cambrian traps.
A new approach has been used to map the deep Cambrian seismic
horizons based on the deep horizon correlation, identification and extension of
deep-seated faults upward in the Cambrian section and their relation to the
induced post-salt structures. This effort has been supported by new seismic
acquisition and processing work focused low frequency, long offset data. This
data has permitted consistent correlations of seismic sequences in the
Paleozoic section and has provided a good match with VSP data.
The approach was used to map the Ordovician Hamra
Quartzites at the new Hassi
Terfa (HTF-1) discovery. The HTF-1 is a very
significant discovery that confirmed the prospectivity
and petroleum potential of the Hassi-Dzabat area. New
mapping demonstrated the presence of fault-bounded, horst-graben
traps and identified the presence of a new sub-uncon-formity
exploration play between Hassi-Messaoud and the Dorban Trough.