We have developed and applied an inverse [Formula: see text] filter formulation using the continuous wavelet transform (CWT), which provides a natural domain for time-variant operations, such as compensation for propagation in attenuating and dispersive media. The well-known linear attenuation model, given as a function of time and frequency, was applied very efficiently over wavelet coefficients in the time-frequency domain to correct for amplitude and phase distortions, as necessary. The inverse CWT yields the recovered trace with a broader bandwidth. The process works on a trace-by-trace basis, making no distinction if the data is pre- or poststack. Our motivation was to develop gather conditioning tools to enhance prestack interpretation techniques such as amplitude variation with offset (AVO) analysis and inversion — a technique that is often compromised by tuning and other propagation related issues that degrade seismic resolution. Thus, we investigated the AVO fidelity of our filter and the sensitivity of the results to incorrect values of [Formula: see text], using real and synthetic data. Our synthetic data experiments clearly showed that AVO anomalies are recovered and preserved in a stable manner, even with values of [Formula: see text] off by 50% of its correct value. The application in time-migrated gathers shows a very natural increase in the vertical definition of the events, especially due to the partial elimination of the tuning effect. The benefits for imaging are also evidenced by comparing stacked sections before and after inverse [Formula: see text] filtering. The higher resolution of seismic sections leads to a better definition of smaller scale stratigraphic and structural features.
Seismic inversion is routinely used to determine rock properties, such as acoustic impedance and porosity, from seismic data. Nonuniqueness of the solutions is a major issue. A good strategy to reduce this inherent ambiguity of the inversion procedure is to introduce stratigraphic and structural information a priori to better construct the low-frequency background model. This is particularly relevant when studying heterogeneous deepwater turbidite reservoirs that form prolific, but complex, hydrocarbon plays in the Brazilian offshore basins. We evaluated a high-resolution inversion workflow applied to 3D seismic data at Marlim Field, Campos Basin, to recover acoustic impedance and porosity of the turbidites reservoirs. The Marlim sandstones consist of an Oligocene/Miocene deepwater turbidite system forming a series of amalgamated bodies. The main advantage of our workflow is to incorporate the interpreter’s knowledge about the local stratigraphy to construct an enhanced background model, and then extract a higher resolution image from the seismic data. High-porosity zones were associated to the reservoirs facies; meanwhile, the nonreservoir facies were identified as low-porosity zones.
We have developed the amplitude versus angle full-waveform inversion (AVA-FWI) method. This method considers the complete seismic response of the layered medium, and so it is capable of correctly handling seismic amplitudes from prestack data with a wide angle range. This capability is very important because a reliable estimate of the elastic parameters and the density requires an incidence angle that goes beyond 30°. Our method inputs seismic traces from prestack time-migrated gathers ordered by angle of incidence and works under the local 1D assumption. AVA-FWI is a nonlinear inversion based on forward modeling by the reflectivity method, which substantially increases its computational cost with respect to conventional AVA inversion. To address this problem, we developed an efficient routine for angle gather modeling and a new method for differential seismogram generation that greatly reduces the amount of computation involved in this task. The AVA-FWI method was applied to synthetic data and to a geophysical reservoir characterization case study using the North Viking Graben open data set.
Extracting full-resolution models from seismic data to minimize systematic errors in inversion: Method and examples C reating an accurate subsurface model is paramount to many geophysical and geological workflows. Examples are background models for seismic inversion, rock property models for reservoir characterization, and geological models of depositional elements for seismic morphological interpretation. The standard workflow for creating subsurface models using seismic data is stratal slicing. The stratal slicing approach, however, may break down in the case of complex stratigraphic or tectonic structuring, such as shelf-to-basin clinoforms, delta lobe switching, deep-water channel-fan complexes, and deformation due to salt tectonics. This paper illustrates how the results obtained with highresolution inversion and the incorporation of a stratigraphically consistent low-frequency model generated through horizon mapping-called the HorizonCube-improves the quality of the estimation of the subsurface parameters in structural complex settings. Using two data examples with different seismic data and geological settings from the North Sea and offshore Brazil, the paper will demonstrate the increased accuracy of the final inversion result using a datadriven HorizonCube. Generalized models: An obstacle to the seismic inversion of reservoir properties Different data and methodologies are available for model building. If only wells are available, a model might be built using manual correlation between logs, interpolation in 3D space, and optional stochastic modeling. The availability of seismic data, however, offers significant advantages as we can now apply data control on the 3D structures described in the model. The standard workflow used for this is stratal slicing, a well established technique for building low-frequency models in model-based seismic inversions (Russell and Hampson, 1991) and a technology often used for the interpretation of seismic geomorphology (Zeng, 1998a, 1998b). The stratal slicing workflow starts with a number of interpreted horizons. These horizons define the top and bottom of packages. Additional intermediate horizons can be modeled using relationships with bounding horizons-typically "proportional," "parallel to upper," "parallel to lower" (Figure 1). This methodology works well in settings with pseudo layercake deposition and gentle tectonic deformation. While stratal slicing is a powerful workflow that is effective in a large number of situations, the stratal slicing approach may break down in the case of complex stratigraphic or tectonic structuring. Examples include shelf-to-basin clinoforms, switching delta lobe geometries, deep-water channelfan complexes, and structuring caused by salt tectonics. In these and other cases, generalized models are no longer valid.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.