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Seismic imaging of thrust fault structures in Zagros iranian oil fields, from surface and well data

Abstract : The Aghajari field is located in the Dezful Embayment, one of major structural zone in Zagros fold-thrust belt containing most of Iranian oil fields. The late Oligocene-early Miocene Asmari formation is one of the main reservoir rocks of SW Iran with several decades of production history from different oil fields in the region. The objective of the present Ph-D thesis is to improve the structural understanding of the Aghajari field using 3D seismic imaging for the first time, and well seismic. the lack of seismic response of the dipping horizons in the reservoir oil zone constitutes a major identified difficulty. Given the dip values of 30° to 45° of the reflectors in the pay zone, the P-P reflections are expected to appear mainly on the horizontal components of the VSP data, justifying the processing of the 3 components (3C). An innovative method of 3C VSP orientation was developed. The 3C VSP results confirm the presence of dipping reflectors, with dip values in agreement with surface seismic, on the eastern flank of the structure. Several new approaches of seismic imaging have been applied in order to investigate and improve the reservoir illumination. The “Beyond Dix” workflow of CGGVERITAS was applied to land seismic data for the first time; this process enables to build a depth/velocity model from the dips read on the PSTM image (pre-stack time migration), and the residual move out corrections. The depth migrated image is improved in the overburden, unfortunately not at reservoir level, due to low signal to noise, interference with multiples, thus poor dip and velocity determination in the reservoir interval. A new Kirchhoff PSTM prototype technique was developed in IFP, allowing a selection of azimuth sector, offset range and geological dip, with automatic optimization of the local dip. The results from this new technique show clear improvements in dip determination and signal to noise ratio of the migrated image. The additional study of another exploration anticline in Zagros, using surface seismic, well data, VSP and geological information illustrates how an integrated data analysis can improve the understanding of deep structures, and therefore help making more reliable drilling decisions, if achieved timely. In Zagros, Surface seismic is definitely a good tool for the structural exploration, but its application to fine reservoir studies has not been demonstrated, in spite of the efforts achieved in the present study.
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https://tel.archives-ouvertes.fr/tel-00403617
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Submitted on : Wednesday, September 9, 2009 - 3:00:57 PM
Last modification on : Wednesday, January 20, 2021 - 3:38:08 AM

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  • HAL Id : tel-00403617, version 2

Citation

Kazem Kazemi. Seismic imaging of thrust fault structures in Zagros iranian oil fields, from surface and well data. Geophysics [physics.geo-ph]. Université de Cergy Pontoise, 2009. English. ⟨tel-00403617v2⟩

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