Refinement Step For Parameter Estimation In The Crs Method

The Common Reflection Surface (CRS) method is a powerful extension of the well established Common Midpoint (CMP) method in the sense that it is able to accept at each trace location on the zero-offset (ZO) section to be constructed, reflection data from source and receiver pairs that are arbitrarily located around that point. The CRS method uses the general hyperbolic moveout, that depends, in the 2D situation considered in this work, on three parameters. One of these parameters is the classical NMO velocity. As in the single-parameter CMP method, the CRS parameters or attributes are estimated by a direct application of suitable coherence analysis to the input multicoverage data. The estimation of the three CRS parameters is generally performed in two steps. The first step has a global character and aims in obtaining an initial estimate of the parameters. The second step has a local character, trying to refine the previous initial values to more accurate values. Here we focus on the refinement step assuming that initial estimates have been already provided. We review and compare three of these methods and compare their performances on illustrative synthetic and real data examples. Comparisons with the application of the conventional CMP method are also provided.213275286BIRGIN, E. et al. Restricted optimization as a due to last and accurate implementation of the common reflection surface stack method. Journal of Applied Geophysics, [S.I.], v. 42, p. 143-155, 1999CASTLE, R. J. A theory of normal move out. Geophysics, [S.I.], v. 59, p. 983-999, 1994CHIRA-OLIVA, P. et al. Formula for a 2D curved measurement surface and finite-offset reflections. Journal of Seismic Eylorotion, [S.I.], v. 10, p. 245-262, 2001GARABITO, G., (2001) Empilhamento de superfícies de reflexão comum: Uma nova seqüência de processamento usando otimização global e local. 2001, , Tese (Doutorado)-Universidade Federal do Pará, BelémGILL, P. E.MURRAY, W.WRIGHT, M. H. Pratical optimization. [S.I.]: Academic Press, 1981HUBRAL, P. Computing true amplitude reflections in a laterally inhomogeneous earth. Geophysics, [S.I.], v. 48, p. 1051-1062, 1983MANN, J. Extensions and application of the common reflection surface stack method. 2002. Thesis (PhD)-University of Karlsruhe, [S.I.], 2002MÜLLER, J. The common reflection surface stack method: seismic imaging without explicit knowledge of the velocity model. 1999. Thesis (PhD)-University of Karlsruhe, [S.I.], 1999NEIDEL, N.TANER, M. Semblance and other coherency measures for multichannel data. Geophysics, [S.I.], v. 36, p. 482-497, 197

Impedance-type approximations of the P-P elastic reflection coefficient: Modeling and AVO inversion

The normal-incidence elastic compressional reflection coefficient admits an exact, simple expression in terms of the acoustic impedance, namely the product of the P-wave velocity and density, at both sides of an interface. With slight modifications a similar expression can, also exactly, express the oblique-incidence acoustic reflection coefficient. A severe limitation on the use of these two reflection coefficients in analyzing seismic reflection data is that they provide no information on shearwave velocities that refer to the interface. We address the natural question of whether a suitable impedance concept can be introduced for which arbitrary P-P reflection coefficients can be expressed in a form analogous to their acoustic counterparts. Although no closed-form exact solution exists, our analysis provides a general framework for which, under suitable restrictions of the medium parameters, possible impedance functions can be derived. In particular, the well-established concept of elastic impedance and the recently introduced concept of reflection impedance can be better understood. Concerning these two impedances, we examine their potential for modeling and for estimating the AVO indicators of intercept and gradient. For typical synthetic examples, we show that the reflection impedance formulation provides consistently better results than those obtained using the elastic impedance.69259259

Nonstretch NMO

We describe a new implementation of the normal-moveout (NMO) correction that is routinely applied to common-midpoint (CMP) reflections prior to stacking. The procedure, called nonstretch NMO, automatically avoids the undesirable stretch effects that are present in conventional NMO. Under nonstretch NMO, a significant range of large offsets that normally would be muted in the case of conventional NMO can be kept and used, thereby leading to better stack and velocity determinations. We illustrate the use of nonstretch NMO by applying it to synthetic and real data sets obtained from high-resolution (HR) seismic and ground-penetrating radar (GPR) measurements.69259960

2-d Zo Crs Stack By Considering An Acquisition Line With Smooth Topography

The land seismic data suffers from effects due to the near surface irregularities and the existence of topography, For obtaining a high resolution seismic image, these effects should be corrected by using seismic processing techniques, e.g. field and residual static corrections. The Common-Reflection- Surface (CRS) stack method is a new processing technique to simulate zero-offset (ZO) seismic sections from multi-coverage seismic data. It is based on a second-order hyperbolic paraxial traveltime approximation referred to a central normal ray. By considering a planar measurement surface, the CRS stacking operator is defined by means of three parameters, namely the emergence angle of the normal ray, the curvature of the normal incidence point (NIP) wave, and the curvature of the normal (N) wave. In this paper the 2-D ZO CRS stack method is modified in order to consider effects due to the smooth topography. By means of this new CRS formalism, we obtain a high resolution ZO seismic section, without applying static corrections. As by-products the 2-D ZO CRS stack method we estimate at each point of the ZO seismic section the three relevant parameters associated to the CRS stack process. © 2005 Sociedade Brasileira de Geofísica.2311525BARD, B., (1974) Nonlinear parameter estimation, , Academic PressBIRGIN, E., BILOTI, R., TYGEL, M., SANTOS, L.T., Restricted optimization: A clue to a fast and accurate implementation of the common reflection surface stack (1999) Journal of Applied Geophysics, 42, pp. 143-155ČERVENÝ, V., PSENSIK, I., (1988) Ray tracing program, , Charles University, CzechoslovakiaCHIRA, P., (2003) Empilhamento pelo método Superfície, , de Reflexão Comum 2-D com topografia e introdução ao caso 3-D, Ph.D. thesis, Federal University of Para, BrazilCHIRA-OLIVA, P., HUBRAL, P., Traveltime formulas of near-zero-offset primary reflections for a curved 2-D measurement surface (2003) Geophysics, 68 (1), pp. 255-261CHIRA-OLIVA, P., TYGEL, M., ZHANG, Y., HUBRAL, P., Analytic CRS stack formula for a 2D curved measurement surface and finite-offset reflections (2001) Journal of Seismic Exploration, 10, pp. 245-262GARABITO, G., CRUZ, J.C., HUBRAL, P., COSTA, J., Common Reflection Surface Stack: A new parameter search strategy by global optimization, 71th, SEG Mtg (2001) Expanded Abstracts, , San Antonio, Texas,USAGILL, P.E., MURRAY, W., WRIGHT, M.H., (1981) Practical optimization, , Academic PressGUO, N., FAGIN, S., Becoming effective velocity-model builders and depth imagers, part 2 - the basics of velocity-model building, examples and discussions Multifocusing (2002) The Leading Edge, pp. 1210-1216HUBRAL, P., Computing true amplitude reflections in a laterally inhomogeneous earth (1983) Geophysics, 48, pp. 1051-1062MANN, J., JÄGER, R., MÜLLER, T., HÖCHT, G., HUBRAL, P., Common-reflection-surface stack - A real data example (1999) Journal of Applied Geophysics, 42, pp. 301-318MÜLLER, T., (1999) The common reflection surface stack method - seismic imaging without explicit knowledge of the velocity model, , Ph.D. Thesis, University of Karlsruhe, GermanySEN, M., STOFFA, P., (1995) Global optimization methods in geophysical inversion, , Elsevier, Science Publ. CoZHANG, Y., HÖCHT, G., HUBRAL, P., 2D and 3D ZO CRS stack for a complex top-surface topography, Expanded (2002) 64th EAGE Conference and Technical Exhibition, , Abstract of th

Inverse Common-Reflection-Surface

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The Common-Reflection-Surface (CRS) stack method is a powerful tool to produce high-quality stacked images of multicoverage seismic data. As a result of the CRS stack, not only a stacked section, but also a number of attributes defined at each point of that section, are produced. In this way, one can think of the CRS stack method as a transformation from data space to attribute space. Being a purely kinematic method, the CRS stack lacks amplitude information that can be useful for many purposes. Here we propose to fill this gap by means of a combined use of a zero-offset section (that could be a short-offset or amplitude-corrected stacked section) and common midpoint gather. We present an algorithm for an inverse CRS transformation, namely one that (approximately) transforms the CRS attributes back to data space. First synthetic tests provide satisfying results for the two simple cases of single dipping-plane and single circular reflectors with a homogeneous overburden, and provide estimates of the range of applicability, in both midpoint and offset directions. We further present an application for interpolating missing traces in a near-surface, high-resolution seismic experiment, conducted in the alluvial plain of the river Gave de Pau, near Assat, southern France, showing its ability to build coherent signals, where recording was not available. A somewhat unexpected good feature of the algorithm, is that it seems capable to reconstruct signals even in muted parts of the section.183313921400Research Foundation of the State of Sao Paulo, BrazilConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)WIT ConsortiumConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

The Influence Of The Available Scattering-vector Range On The Retrieval Of Particle-size Distributions From Small-angle Scattering Intensity Data

The determination of the particle-size distribution [D(r)J from small-angle scattering intensity data is discussed. The influence of the maximum available scattering vector hmax on D(r) retrieval is investigated with the help of numerical experiments with previously known solutions. The numerical corrector method provides a good answer even in cases where hmax is much smaller than those values necessary with other retrieval methods. © 1997 International Union of Crystallography all rights reserved.305 PART 2808810Fedorova, I.S., Schmidt, P.W., (1978) J. Appl. Cryst., 11, pp. 405-411Glatter, O., (1977) J. Appl. Cryst., 10, pp. 415-421Glatter, O., (1980) J. Appl Cryst., 13, pp. 7-11Glatter, O., Kratky, O., (1982) Small Angle X-ray Scattering, , New York: Academic PressGuinier, A., Fournet, A., (1955) Small Angle Scattering of X-rays, , New York: John WileyMulato, M., Chambouleyron, I., (1996) J. Appl. Cryst., 29, pp. 29-3

PULSE DISTORTION IN-DEPTH MIGRATION

When migrating seismic primary reflections obtained from arbitrary source-receiver configurations (e.g., common shot or constant offset) into depth, a pulse distortion occurs along the reflector. This distortion exists even if the migration was performed using the correct velocity model. Regardless of the migration algorithm, this distortion is a consequence of varying reflection angle, reflector dip, and/or velocity variation. The relationship between the original time pulse and the depth pulse after migration can be explained and quantified in terms of a prestack, Kirchhoff-type, diffraction-stack migration theory.59101561156

Recuperação De Atributos Sísmicos Utilizando A Migração Para Afastamento Nulo

A conventional processing, without a reliable adjustment in order to preserve the seismic amplitudes, could damage the mapping of the petrophysical properties, jeopardizing the correlation between the seismic data and the well profile. A manner to estimate correctly the amplitudes and, therefore, the reflection coefficients is to perform a pre-stack migration in true amplitude, where an amplitude distortion caused by the geometrical spreading throughout the ray path is compensated by the migration calculation. Nevertheless, this process has an expensive cost as well as is dependent from the velocity model. A routine less expensive than the other one and also more stable taking into account the velocity model, is to transform the seismic section obtained from the acquisition in common offsets in simulated section in zero offset with true amplitudes. This transformation is called true amplitude Zero Offset migration (TA MZO). In a media with constant velocity, the stack curve for the MZO and the weight function are reduced in analytic formulas, mitigating the computational effort. This work has two main objects: the first is to verify the TA MZO algorithm efficiency for a constant velocity in a synthetic model to a complex geology based on a Neo-Albian turbidity reservoir, where the assumption of constant velocity is not respected. The second one is to perform quantitative studies as results of the technique described above. Likewise, the study tries to analyze how useful is the methodology to compute the graphics for AVO and AVA analyses, helping the reservoir characterization.2015965Bleistein, N., Two and one half dimensional in plane wave propagation (1986) Geophysical Prospecting, 34, pp. 686-703. , S.IBleistein, N., Cohen, J., Jaramillo, H., True-amplitude transformation to zero offset of data from curved reflectors (1999) Geophysics, 64, pp. 112-129. , TulsaHubral, P., Tygel, M., Zien, H., Three-dimensional true-amplitude zero-offset migration (1991) Geophysics, 56, pp. 18-26. , TulsaSchleicher, J., A unified approach to 3D seismic reflection imaging. Part I: Basic concepts (1996) Geophysics, 61, pp. 742-758. , TulsaOliveira, A.S., Tygel, M., Filpo, E., On the application of true-amplitude DMO (1997) Journal of Seismic Exploration, 6, pp. 279-289. , Castelnau-le-LezRamos, A.C.B., True amplitude MZO and AVO: Application to real data (1997) International Congress of the Brazilian Geophysical Society, 1, pp. 223-226. , 5., 1997, Rio de Janeiro. Proceedings. [Rio de Janeiro: SBGf], Expanded AbstractTygel, M., Multiple Weights in diffraction stack migration (1993) Geophysics, 59, pp. 1820-1830. , TulsaTygel, M., Schleicher, J., Hubral, P., Kirchhoff-Helmholtz theory in modelling and migration (1994) Journal of Seismic Exploration, 3, pp. 203-214. , Castelnau-le-LezP. Pulse distortion in deph migration (1994) Geophysics, 59, pp. 1561-1569. , TulsaTygel, M., Schleicher, J., Hubral, P., Dualities involving reflectors and reflection-time surfaces (1995) Journal of Seismic Exploration, 4, pp. 123-150. , Castelnau-le-LezTygel, M., Schleicher, J., Hubral, P., A unified approach to 3D seismic reflection imaging Part II: Theory (1996) Geophysics, 61, pp. 759-775. , TulsaTygel, M., Schleicher, J., Hubral, P., 2,5D Kirchhoff MZO in laterally inhomogeneous media (1998) Geophysics, 63, pp. 557-573. , TulsaTygel, M., Kirchhoff imaging for AVO/AVA (1999) The Leading Edge, 18, pp. 940-945. , S.

Seismic Imaging

[No abstract available]201

The common reflecting element (CRE) method revisited

The common reflecting element (CRE) method is an interesting alternative to the familiar methods of common midpoint (CMP) stack or migration to zero offset (MZO). Like these two methods, the CRE method aims at constructing a stacked zero-offset section from a set of constant-offset sections. However, it requires no more knowledge about the generally laterally inhomogeneous subsurface model than the near-surface values of the velocity field. In addition to being a tool to construct a stacked zero-offset section, the CRE method simultaneously obtains information about the laterally inhomogeneous macrovelocity model. An important feature of the CRE method is that it does not suffer from pulse stretch. Moreover, it gives an alternative solution for conflicting dip problems. In the 1-D case, CRE is closely related to the optical stack. For the price of having to search for two data-derived parameters instead of one, the CRE method provides important advantages over the conventional CMP stack. Its results are similar to those of the MZO process, which is commonly implemented as an NMO correction followed by a dip moveout (DMO) correction applied to the original constant-offset section. The CRE method is based on 2-D kinematic considerations only and is not an amplitude-preserving process.65397999