Redatumação Kirchhoff por soma única para dados sísmicos de múltipla cobertura
We present a new redatuming approach to correct the distortions caused by the rough topography and the weathering layer, which is usually inhomogeneous, in land multiple coverage seismic data. The redatuming method is physically more justified than the commonly used static correction methods, whi...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/52814 |
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| Resumo: | We present a new redatuming approach to correct the distortions caused by the rough
topography and the weathering layer, which is usually inhomogeneous, in land multiple
coverage seismic data. The redatuming method is physically more justified than the commonly
used static correction methods, which provide - in indicated situations - non-physical
adjustments (field static) by displacing the traces in time, which leads to sub-optimal reflections
imaging and inversion. The redatuming procedure offered here is different: it transforms
irregular multiple coverage reflection seismic data on an uneven surface in a pre-specified flat
datum in a regular configuration of sources and receivers, below the complex speed zone. This
is done by adding/stacking the input traces along traveltime curves or Kirchhoff type operators
that are calculated by ray tracing. In this way, distorted reflections and diffractions in the input
data become more regular (for example, hyperbolic) and, thus, recognizable in the output data.
For this to happen, Kirchhoff single-stack redatuming operator needs an approximation of the
weathering zone speed. Then, multiple coverage output data on the new flat datum can be
imaged and inverted more reliably than with standard static correction methods. This thesis
presents a review of the theoretical approach to Kirchhoff redatuming based on a single
summation and proposes development of a new redatuming algorithm for multiple-coverage
pre-stack seismic data. The validation of this algorithm is done by applying it to controlled
seismic data generated from synthetic models representing real geological situations. This
thesis also presents a study on the sensitivity of the Kirchhoff single-sum redatuming algorithm
to velocity model errors. To this end, we used information from the velocities of the weathering
zone and shallow structures obtained by two commonly used refraction traveltime tomography
algorithms in seismic (Rayinvr and Refratom) and compared the redatuming done in each case
to verify the influence of the velocity model on the redatuming. The results show that the
presented redatuming adequately corrects for the effects of topography and weathering zone
using more accurate models, producing depth migrated images with correct positioning of the
reflectors. Applying the redatuming algorithm to poor quality 2D land seismic data provided
interpolated and regularized prestack redatumed data, whose depth migrated images show
improved quality and increased signal-to-noise ratio, with enhanced and more continuous reflector. |
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