How thin is a thin bed? An alternative perspective

Zeng, Hongliu

doi:10.1190/1.3249773

Cited by 27 publications

(6 citation statements)

References 4 publications

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“…The seismic signal was sampled every 2 ms prior to the application of an anti-aliasing filter, giving a vertical resolution of at least 2 ms for λ/4. The calculated vertical resolution is a conservative value, as resolution reaches values of λ/8 or λ/32 in thin beds (Zeng, 2009). The data were zero-phased migrated with a bin spacing of 12.5 × 12.5 m. The processing sequence of the data included resampling, spherical divergence corrections, and zero-phase conversions undertaken prior to stacking, 3-D prestack time migra tion using the Stolt algorithm, and one-pass 3-D migration.…”

Section: Methodsmentioning

confidence: 99%

Differential compaction over Late Miocene submarine channels in SE Brazil: Implications for trap formation

2017

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We used high-quality three-dimensional (3-D) seismic data to quantify the timing and magnitude of differential compaction over a Late Miocene submarine channel complex in SE Brazil (Espírito Santo Basin). A thicknessrelief method was applied to quantify the thickness variations in strata deposited over the channel complex. We found that differential compaction started after the channel complex was buried by ~200 m of strata, as revealed by thinning horizons observed over a compaction-related anticline. The size of the anticline is greatest in the south of the study area, reaching heights of 41 ms (~50 m). Fluid expelled through faults on the margins of the channel complex formed large depressions. These depressions increased in size after deep-water currents removed the fluid-rich sediment filling them. Differential compaction also occurred over deposits downslope of knickpoints, reaching maximum heights of 29 ms (~35 m). Seismic reflections onlap the knickpoint face and are believed to comprise slumped strata and debrites. Two-way traveltime isochron and amplitude maps indicate that there are limited connectivity and lateral continuity of the coarse-grained units. Differential compaction over these deposits created anticlines with four-way dip closure. As a consequence, isolated reservoirs were closed vertically by the compaction anticlines and laterally by strata onlapping the knickpoint face. These unique reservoirs could have been charged by migration of hydrocarbons along sands at the base of the channel complex. A fill-to-spill model is hypothesized using the above mechanism: Once an isolated anticlinal trap reached spill point, hydrocarbons migrated upslope into the next trap. Traps like these could form above submarine channels in similar basins around the world (e.g., Gulf of Mexico, west coast of Africa) after early burial.

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Section: Methodsmentioning

confidence: 99%

Differential compaction over Late Miocene submarine channels in SE Brazil: Implications for trap formation

2017

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“…The vertical resolution depends on the velocity of EM waves and the frequency of the antennae used. Following the λ/4 criterion (Widess 1973;Jol 1995;Zeng 2009), it varies from 70 to 5 cm for frequencies of 50-500 MHz and velocities of 0.1-0.14 m ns −1 . In general, features such as sedimentary structures, lithological boundaries, fractures and/or faults are clearly visible with GPR (Gross et al 2004;Neal 2004;Deparis et al 2007;McClymont et al 2010), even when these features differ only by small changes in the nature, size, shape, orientation and packing of grains (Guillemoteau et al 2012).…”

Section: Methodology Of Gpr Acquisitionmentioning

confidence: 99%

GPR measurements to assess the Emeelt active fault's characteristics in a highly smooth topographic context, Mongolia

Dujardin

Bano

Schlupp

et al. 2014

Geophysical Journal International

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To estimate the seismic hazard, the geometry (dip, length and orientation) and the dynamics (type of displacements and amplitude) of the faults in the area of interest need to be understood. In this paper, in addition to geomorphologic observations, we present the results of two ground penetrating radar (GPR) campaigns conducted in 2010 and 2011 along the Emeelt fault in the vicinity of Ulaanbaatar, capital of Mongolia, located in an intracontinental region with low deformation rate that induces long recurrence time between large earthquakes. As the geomorphology induced by the fault activity has been highly smoothed by erosion processes since the last event, the fault location and geometry is difficult to determine precisely. However, by using GPR first, a non-destructive and fast investigation, the fault and the sedimentary deposits near the surface can be characterized and the results can be used for the choice of trench location. GPR was performed with a 50 MHz antenna over 2-D lines and with a 500 MHz antenna for pseudo-3-D surveys. The 500 MHz GPR profiles show a good consistency with the trench observations, dug next to the pseudo-3-D surveys. The 3-D 500 MHz GPR imaging of a palaeochannel crossed by the fault allowed us to estimate its lateral displacement to be about 2 m. This is consistent with a right lateral strike-slip displacement induced by an earthquake around magnitude 7 or several around magnitude 6. The 2-D 50 MHz profiles, recorded perpendicular to the fault, show a strong reflection dipping to the NE, which corresponds to the fault plane. Those profiles provided complementary information on the fault such as its location at shallow depth, its dip angle (from 23 • to 35 •) and define its lateral extension.

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“…However, these advantages rest on the assumption that the reflection comes from a single interface, or that the seismic data have enough resolution to resolve individual reflections from the top and bottom of a bed (Zeng and Backus, 2005a). For a thin bed with unresolved top and bottom in its composite response, Zeng andBackus (2005a, 2005b) analyze the phase effects on the interference pattern and conclude that a 90°-phase wavelet is more desirable for the identification of thin beds.…”

Section: Zero-crossing Timesmentioning

confidence: 98%

“…Seismic data interpreters have to resort to the art of geologic interpretation based on their knowledge of the basic principles of geology and seismic attributes and their experience and intuition (Chopra et al, 2006). Zeng (2009) proposes a new resolution definition, bed resolution, which emphasizes thin-bed identification rather than interface separation. It is easier to identify a thin bed via inspection of attribute slices than to resolve it via a seismic section.…”

Section: Introductionmentioning

confidence: 99%

Characterization of interbedded thin beds using zero-crossing-time amplitude stratal slices

Sacchi

Wang

et al. 2015

GEOPHYSICS

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We have developed a novel method to characterize thin beds using zero-crossing-time (ZCT) amplitude slices based on an interesting phenomenon we have noticed. Because of the reflection interferences and wavelet overlap, it is almost impossible to identify each thin bed from the composite response of interbedded thin beds. However, the seismic response of one thin bed does not always interfere with other thin beds at all times. At its ZCTs, a thin bed's reflection makes no contribution to the composite response. Therefore, unlike standard amplitude stratal slices, the imprint of a thin bed does not appear in its ZCT amplitude stratal slices. The latter makes the interference pattern of ZCT amplitude stratal slices different from those of other amplitude stratal slices. Based on this difference, the ZCT amplitude stratal slices of each thin bed can be identified from consecutive amplitude slices, and the thickness, depth, and lateral distribution of each thin bed, as well as the vertical spacing between them, can be estimated from their ZCTs. This interpretive method has been systematically tested with synthetic 3D data and has also been applied to field seismic data.

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How thin is a thin bed? An alternative perspective

Cited by 27 publications

References 4 publications

Differential compaction over Late Miocene submarine channels in SE Brazil: Implications for trap formation

Differential compaction over Late Miocene submarine channels in SE Brazil: Implications for trap formation

GPR measurements to assess the Emeelt active fault's characteristics in a highly smooth topographic context, Mongolia

Characterization of interbedded thin beds using zero-crossing-time amplitude stratal slices

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