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12th International Congress of the Brazilian Geophysical Society
- Conference date: 15 Aug 2011 - 18 Aug 2011
- Location: Rio de Janeiro, Brazil
- Published: 15 August 2011
461 - 465 of 465 results
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Legacy of Luiz Rijo in MT Exploration at the University of Utah and Beyond: Two-Dimensional Inversion and Frontier Solid-Earth Investigations
More LessAmong his many important research and educational contributions, one of the first developments of Professor Luiz Rijo (while still a graduate student) was a basic but powerful finite element algorithm for modeling twodimensional inductive EM scattering from Earth resistivity structure. Following additional efforts by colleagues and peers, this code became the basis for generalized platforms widely used to simulate and invert land, marine and airborne plane-wave data. The author’s experience in this technology emphasizes application to solid-earth and geothermal exploration field studies including the Great Basin, New Zealand and Antarctica where unique insights from resistivity structure have been possible.
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Modified Gauss-Newton With Sparse Updates
Authors Xiang Li, Aleksandr Aravkin, Tristan van Leeuwen and and Felix J.HerrmannFull-waveform inversion (FWI) is a data fitting procedure that relies on the collection of seismic data volumes and sophisticated computing to create high-resolution models. With the advent of FWI, the improvements in acquisition and inversion have been substantial, but these improvements come at a high cost because FWI involves extremely large multi-experiment data volumes. The main obstacle is the ‘curse of dimensionality’ exemplified by Nyquist’s sampling criterion, which puts a disproportionate strain on current acquisition and processing systems as the size and desired resolution increases. In this paper, we address the ‘curse of dimensionality’ by using randomized dimensionality reduction of the FWI problem, coupled with a modified Gauss-Newton (GN)
method designed to promote curvelet-domain sparsity of model updates. We solve for these updates using the spectral projected gradient method, implemented in the SPG`1 software package. Our approach is successful because it reduces the size of seismic
data volumes without loss of information. With this reduction, we can compute Gauss-Newton updates with the reduced data volume at the cost of roughly one gradient update for the fully sampled wavefield.
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Combining Seismic Data Preconditioning, Avo Inversion and Geometrical Attributes for High Resolution Reservoir Delineation
More LessWe show how conventional AVO inversion can be pushed further as a reservoir delineation tool, if viewed as part of larger workflow, which includes gather preconditioning, to increase signal-to-noise ratio and vertical resolution of the seismic data, in addition to an automatic detailed stratigraphic interpretation for reliable background model building. Our strategy includes carrying the whole inversion in a form independent on the low frequency information to retrieve only variations of P and S-wave impedances and density. The estimated models are then combined with their corresponding background model derived using the horizon cube technology. Application to an offshore marine data set illustrates the advantages this methodology brings to prospect evaluation.
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Reservoir Characterization: Which Rock Physics Input Should You Put?
More LessSeismic rock physics is a powerful tool for reservoir characterization. Seismic data has a moderate resolution, but a terrific lateral and volumetric continuity, and may be the main driver for reservoir properties estimation. Reservoir seismic properties, e.g. impedances, velocities and even density, can be extracted from seismic volumes and these properties very often contains a lot of petrophysical and litological information. Nowadays there are some efforts trying to extract the petrophysical information directly from the seismic data volumes, without the intermediate step of seismic property estimation. Nevertheless, these data must be calibrated and validated with similar data obtained from more direct measurements, like sonic logs and laboratory experiments, in order to achieve a good quantitative match, no matter what inversion scheme is used. Some strength, as well as some caveats, of rock physics data will be discussed on this paper. The aim of it is not to suggest any ground truth or rule of thumb, but ratter to
provoke the discussion of this interesting subject.
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Reservoir Seismic Characterization of Brazilian Offshore and Pre-Salt Fields
By Paulo JohannThis paper focuses on the strong impact that seismic technology has had on the production development of the Brazilian marine hydrocarbon fields starting from the first oil discovery in 1968 (Guaricema field) to 2006, when the pre-salt new province was revealed in Santos basin. The evolution of three main knowledge areas of seismic technology will be detailed, namely: acquisition, processing and interpretation. Seismic acquisition technology has experienced an increase in “information density” (seismic traces per square kilometer) which grew by one order of magnitude from less than 100,000 to 1,024,000), from 1978 (first 3D in Brazil) to 2010. In the seismic processing domain, the improvement of seismic algorithms and methodologies has allowed for better seismic data quality, resolution and imaging. In particular, the algorithms/techniques of 3D multiple suppression and 3D depth migration have significantly evolved in recent years. In the seismic interpretation area, geological context-oriented seismic attributes
algorithms/methodologies have made possible better reservoir characterization and monitoring in the deep and ultra deep-water Brazilian offshore basins.
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