Elastic impedance normalization

Whitcombe, David N.

doi:10.1190/1.1451331

Cited by 195 publications

(37 citation statements)

References 2 publications

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“…The inversion scheme presents the theoretical advantage of replacing the gradient reflectivity, generally showing a low S=N and requiring careful log calibration (Whitcombe, 2002) with time-shift data. In fact, this substitution results in a large reduction of the error in changes in saturation that compensates a relatively small increase for the error in DP.…”

Section: Discussionmentioning

confidence: 99%

Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis

et al. 2011

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A reliable estimate of reservoir pressure and fluid saturation changes from time-lapse seismic data is difficult to obtain. Existing methods generally suffer from leakage between the estimated parameters. We propose a new method using different combinations of time-lapse seismic attributes based on four equations: two expressing changes in prestack AVO attributes (zero-offset and gradient reflectivities), and two expressing poststack time-shifts of compressional and shear waves as functions of production-induced changes in fluid properties. The effect of using different approximations of these equations was tested on a realistic, synthetic reservoir, where seismic data have been simulated during the 30-year lifetime of a water-flooded oil reservoir. Results found the importance of the porosity in the inversion with a clear attenuation of the porosity imprint on the final estimates in case the porosity field or the vertically averaged porosity field is known a priori. The use of a first-order approximation of the gradient reflectivity equation leads to severely biased estimates of changes in saturation and leakage between the two different parameters. Both the bias and the leakage can be reduced, if not eliminated, by including higher-order terms in the description of the gradient, or by replacing the gradient equation with P-and/or S-wave time-shift data. The final estimates are relatively robust to random noise, as they present fairly high accuracy in the presence of white noise with a standard deviation of 15%. The introduction of systematic noise decreases the inversion accuracy more severely.

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Section: Discussionmentioning

confidence: 99%

Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis

et al. 2011

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“…The original isotropic P-wave EI equation was presented by Connolly (1999) and refined by Whitcombe (2002) and Martins (2003). Incorporation of arbitrary-symmetry anisotropy into the P-wave EI formula is described in Martins (2006).…”

Section: Methodsmentioning

confidence: 99%

“…Selection of normalizing constants ρ 0 , α 0 , β 0 , G 0 = ρ 0 β 2 0 and EI 0 = ρ 0 α 0 at a specific depth facilitates correlation of AI and EI in the same units (Whitcombe, 2002). However, although Eq.…”

Section: Isotropic and Anisotropic Ei Formulasmentioning

confidence: 99%

Spatial variation of angle-dependent impedance through a thin-layered oil reservoir

Oliveira¹,

Martins²

2011

Rev. Bras. Geof.

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ABSTRACT. The P-wave elastic impedance (EI) concept is currently used as a complementary petrophysical parameter for the characterization of oil and gas reservoirs. In this paper, we construct maps representing the spatial variation of isotropic and anisotropic EI at a specific depth through a turbiditic oil-producing reservoir.EI is thus used here not for calibration and inversion of seismic data at farther offsets as firstly introduced, but as an original application of a novel petrophysical concept.As long as bulk density, seismic velocities and incidence angle are common variables in the isotropic and anisotropic EI formulas, we used geophysical measurements at the surroundings of 39 wells drilled through the reservoir formation in order to generate isotropic and anisotropic EI maps. The reservoir inner structure consists of fine layering, allowing us to approximate the formation to a transverse isotropic medium with vertical axis of symmetry (VTI medium) for anisotropic EI map construction. We then applied the Backus-averaging technique for estimating VTI elastic stiffness logs from the well log measurements through the reservoir formation.For the construction of the maps, we implemented an interpolation process incorporating a robust inverse-distance square-weighted interpolator into a search radius scheme. In this scheme, only control points inside a distance specified a priori are considered in the interpolation process. The resulting EI maps for incidence angles of 0 • , 20 • and 40 • , at 3080 m depth, reveal zones of fine layering around certain wells. We observed that seismic anisotropy induced by fine layering is pronounced in these zones, coinciding with low oil-producing intervals. At the same selected depth of the reservoir formation, the remaining parts of the maps show a weak strength of VTI anisotropy.Keywords: geophysical well logs, elastic impedance, seismic anisotropy, Backus-averaging, spatial data interpolation, Namorado reservoir.RESUMO. O conceito de impedância elástica (EI) da onda compressionalé atualmente usado como um parâmetro petrofísico complementar para a caracterização de reservatórios de petróleo e gás. Neste artigo, construímos mapas que representam a variação espacial da EI isotrópica e anisotrópica a uma profundidade específica através de um reservatório turbidítico produtor de petróleo e gás. EIé então usada aqui não para calibração e inversão de dados sísmicos de grandes afastamentos como proposto originalmente, mas como uma aplicação original de um conceito petrofísico novo. Uma vez que densidade efetiva, velocidades sísmicas eângulo de incidência são variáveis comuns nas fórmulas isotrópica e anisotrópica da EI, usamos registros geofísicos nas vizinhanças de 39 poços perfurados através da formação que contém o reservatório a fim de gerar mapas isotrópicos e anisotrópicos de EI. A estrutura interna do reservatório consiste de camadas delgadas, o que nos permitiu aproximar a formação a um meio transversalmente isotrópico com eixo de simetria vertical (meio TIV) para const...

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“…This is more advantageous in the extraction of pre-stack parameters. Whitcombe (2002) first applied a new normalized form of elastic impedance to improve the stability of parameter extraction. Additionally, Martins (2006) and Cui et al (2010) introduced P-and P-SV wave elastic impedance in weakly anisotropic media, respectively.…”

Section: Introductionmentioning

confidence: 99%

Seismic fluid identification using a nonlinear elastic impedance inversion method based on a fast Markov chain Monte Carlo method

Zhang

Pan

et al. 2015

Pet. Sci.

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Elastic impedance inversion with high efficiency and high stability has become one of the main directions of seismic pre-stack inversion. The nonlinear elastic impedance inversion method based on a fast Markov chain Monte Carlo (MCMC) method is proposed in this paper, combining conventional MCMC method based on global optimization with a preconditioned conjugate gradient (PCG) algorithm based on local optimization, so this method does not depend strongly on the initial model. It converges to the global optimum quickly and efficiently on the condition that efficiency and stability of inversion are both taken into consideration at the same time. The test data verify the feasibility and robustness of the method, and based on this method, we extract the effective pore-fluid bulk modulus, which is applied to reservoir fluid identification and detection, and consequently, a better result has been achieved.

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Elastic impedance normalization

Cited by 195 publications

References 2 publications

Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis

Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis

Spatial variation of angle-dependent impedance through a thin-layered oil reservoir

Seismic fluid identification using a nonlinear elastic impedance inversion method based on a fast Markov chain Monte Carlo method

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