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Subcrop Mapping Using Seismic Attribute
Extraction,
Ouazar, Abdelkader, Amin Bellahcene, Sonatrach - Exploration Division -
Triassic province is characterized by one of most important play
of the algerian mining
domain. This play is part of the petroleum system which is generally
structurally controlled. The traps are fault related. The reservoir is
represented by sandstones of continental deposits type, they are charged by the
Silurian source rock. The juxtaposition of the Silurian source rock immediately
under reservoirs units represents one of the major risks of this play. The
assessment of the presence of the source rock (Silurian Shale) under The Hercynian Unconformity, either by conventional technics of interpretation, or by
drillings remain very difficult. Nevertheless, a fine analysis of seismic
amplitudes may help to solve this problem. This technic
allows the identification of the different underlying formations and in particular
units of the Silurian. The approach can be subdivided in four (4) steps: -1st
step: Modelling of reflection coefficients according
to the different lithologies. -2nd step:
Characterization of the seismic signature bounded to the presence of the
Silurian under The Hercynian Unconformity. -3rd step:
Assessment of the “ Tuning effect “ on the seismic signature.
-4th step: Removal of the shallow layers effect on the seismic signature
(absorption, heterogeneity…) by normalizing of amplitudes at the ‘Hercynian Unconformity’ relatively to the amplitude effect
bound to the Lias “S3”. Construction of ratio map (Hercynian Unconformity / S3).
This method
allows the mapping in Pseudo - subcrop map at the Hercynian Unconformity characterizing then the distribution
of the source rock in the absence of wells.