Extended elastic impedance for fluid and lithology prediction

Whitcombe, David N.; Connolly, Patrick; Reagan, Roger L.; Redshaw, T.

doi:10.1190/1.1815660

Cited by 186 publications

(32 citation statements)

References 2 publications

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“…The impact of an inaccurate velocity model on the AVA is explored along with assessing the facies prediction through the extended elastic impedance (Whitcombe et al . ). Finally, a 3D marine data are migrated and benched against a synthetic angle common image gathers generated from a well log.…”

Section: Examplesmentioning

confidence: 97%

Pre‐stack Kirchhoff depth migration local space‐shift imaging condition: synthetic and data examples

O’Brien¹,

Delaney²,

Igoe³

2019

Geophysical Prospecting

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A B S T R A C TExtracting accurate common image angle gathers from pre-stack depth migrations is important in the generation of any incremental uplift to the amplitude versus angle attributes and seismic inversions that can lead to significant impacts in exploration and development success. The commonly used Kirchhoff migration outputs surface common offset image gathers that require a transformation to angle gathers for amplitude versus angle analysis. The accuracy of this transformation is one of the factors that determine the robustness of the amplitude versus angle measurements. Here, we investigate the possibility of implementing an extended imaging condition, focusing on the space-lag condition, for generating subsurface reflection angle gathers within a Kirchhoff migration. The objective is to determine if exploiting the spatial local shift imaging condition can provide any increase in angle gather fidelity relative to the common offset image gathers. The same restrictions with a ray-based approach will apply using the extended imaging condition as both the offset and extended imaging condition method use travel times derived from solutions to an Eikonal equation. The aims are to offer an alternative ray-based method to generate subsurface angle gathers and to understand the impact on the amplitude versus angle response. To this end, the implementation of the space-shift imaging condition is discussed and results of three different data sets are presented. A layered three-dimensional model and a complex two-dimensional model are used to assess the space shift image gathers output from such a migration scheme and to evaluate the seismic attributes relative to the traditional surface offset common image gathers. The synthetic results show that the extended imaging condition clearly provides an uplift in the measured amplitude versus angle over the surface offset migration. The noise profile post-migration is also improved for the space-lag migration due to the double summation inside the migration. Finally, we show an example of a space-lag gather from deep marine data and compare the resultant angle gathers with those generated from an offset migration and a time-shift imaging condition Kirchhoff migration. The comparison of the real data with a well log shows that the space-lag result is a better match to the well compared to the time-lag extended imaging condition and the common offset Kirchhoff migration. Overall, the results from the synthetics and real data show that a Kirchhoff migration with an extended imaging condition is capable of generating subsurface angle gathers with an * Pre-stack Kirchhoff depth migration 1185 incremental improvement in amplitude versus angle fidelity and lower noise but comes at a higher computational cost.

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Section: Examplesmentioning

confidence: 97%

Pre‐stack Kirchhoff depth migration local space‐shift imaging condition: synthetic and data examples

O’Brien¹,

Delaney²,

Igoe³

2019

Geophysical Prospecting

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“…(3) is that its value dramatically decreases with incident angle, which probably lose some information for analyzing elastic impedance at near and far angles, for example, the difference of fluid or lithology change. Therefore, in order to eliminate the effects, Whitcombe et al [3] deduced a new formula of EI by normalizing the original EI equation, as follows…”

Section: The Definition Of Elastic Impedance and Extended Elastic Impmentioning

confidence: 99%

“…(4) can remove the effect of dramatic EI decrease with incident angle θ and keep the same orders of magnitude with post-stack acoustic impedance, the reflectivity R(θ) are probably larger than 1 conflicting with the real seismic recorder. Thus, Whitcombe [3] further modified the EI equation, and replaced sin 2 θ by tanχ (χ is theoretical incident angle being expanded, which changes between −90 • and 90 • ), scaled the reflectivity R(θ) by multiplication by cos χ. The so-called extended elastic impedance (EEI) can be formulated as…”

Section: The Definition Of Elastic Impedance and Extended Elastic Impmentioning

confidence: 99%

“…Recently, a great quantity of research work for EI has been done by scientists in China and abroad. In order to overcome the drawback of incident angle restriction and the rapid variation of inversion results with incident angle which gives rise to difficulties for interpretation, Whitcombe et al [2,3] deduced the expression of the extended elastic impedance (EEI) by modifying the original equation of the EI established by Connoly, which makes it more suitable for fluid discrimination and lithology prediction. They calculated the distribution map of lithology impedance and fluid impedance using EEI in an oil field of North Sea and obtained the distinct imaging map of their channel system.…”

Section: Introductionmentioning

confidence: 99%

“…However, various case studies show [14∼17] that AVO response for carbonate reservoirs is weaker than the clastic reservoirs. Difficulties were encountered when we discriminated fluid for carbonate reservoirs under the optimal incident angle according to the literature [3] because all EEI values indicate low value abnormity for gas-bearing or water-bearing reservoirs, even under the optimal incident angle. We can effectively predict reservoirs, but it is beyond its capabilities to use the above-mentioned method for evaluating the reservoir quality and discriminating gas-or water-content.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Discriminating Gas and Water Using Multi‐Angle Extended Elastic Impedance Inversion in Carbonate Reservoirs

Peng

et al. 2008

Chinese J of Geophysics

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AVO response for carbonate reservoirs is weaker than the clastic reservoirs. So it is very hard to discriminate fluid in carbonate reservoirs using elastic impedance (EI), even under the optimal incident angle. In this paper, a novel method is proposed for discriminating fluid using multi‐angle extended elastic impedance (MEEI) inversion in carbonate reservoirs. We established the fluid‐bearing patterns and effective criterions for discriminating gas and water by calculating MEEI of target layers using the known well data. MEEI inversion of real seismic data shows that we can judge whether the reservoir is good or bad or is gas‐bearing or water‐bearing by observing EEI change trend with various incident angles. The efficiency of the proposed method is validated by the practical application of real seismic data in Sichuan basin.

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Seismic Reservoir Characterization

Kumar

2021

Encyclopedia of Solid Earth Geophysics

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Extended elastic impedance for fluid and lithology prediction

Cited by 186 publications

References 2 publications

Pre‐stack Kirchhoff depth migration local space‐shift imaging condition: synthetic and data examples

Pre‐stack Kirchhoff depth migration local space‐shift imaging condition: synthetic and data examples

Discriminating Gas and Water Using Multi‐Angle Extended Elastic Impedance Inversion in Carbonate Reservoirs

Seismic Reservoir Characterization

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