Wavelet dispersion and bright spot detection

Luh, Peter C.

doi:10.1190/1.1892493

Cited by 4 publications

(4 citation statements)

References 2 publications

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“…Wave motion is gradually absorbed by the medium and reappears in the form of heat. In absorbing media, the amplitude decay occurs exponentially with r (Luh 1993). In this study, the absorption has been restored for the centre frequency of 60 Hz and an effective quality factor Q P of 200 for P-waves was used for layers between the seafloor and the BSR.…”

Section: Absorptionmentioning

confidence: 99%

AVO study of a gas‐hydrate deposit, offshore Costa Rica

Müller

Bönnemann

Neben

2007

Geophysical Prospecting

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A B S T R A C TAmplitude variation with offset (AVO) analysis and waveform inversion are techniques used to determine qualitative or quantitative information on gas hydrates and free gas in sediments. However, the quantitative contribution of gas hydrates to the acoustic impedance contrast observed at the bottom-simulating reflector and the reliability of quantitative AVO analyses are still topics of discussion. In this study, common-midpoint gathers from multichannel wide-angle reflection seismic data, acquired offshore Costa Rica, have been processed to preserve true amplitude information at the bottom-simulating reflector for a quantitative AVO analysis incorporating angles of incidence of up to 60 • . Corrections were applied for effects that significantly alter the observed amplitudes, such as the source directivity. AVO and rock-physics modelling indicate that free gas immediately beneath the gas-hydrate stability zone can be detected and low concentrations can be quantified from AVO analysis, whereas the offset-dependent reflectivity is not sensitive to gas-hydrate concentrations of less than about 10% at the base of the gas-hydrate stability zone. Bulk free-gas saturations up to 5% have been determined from the reflection seismic data assuming a homogeneous distribution of free gas in the sediment. Assuming a patchy distribution of free gas increases the estimated concentrations up to 14%.There is a patchy occurrence of bottom-simulating reflectors south-east of the Nicoya Peninsula on the continental margin, offshore Costa Rica. AVO analysis indicates that this phenomenon is related to the local presence of free gas beneath the gas-hydrate stability zone, probably related to a focused vertical fluid flow. In areas without bottom-simulating reflectors, the results indicate that no free gas is present.

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Section: Absorptionmentioning

confidence: 99%

AVO study of a gas‐hydrate deposit, offshore Costa Rica

Müller

Bönnemann

Neben

2007

Geophysical Prospecting

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“…The selection of scale is based on the desired frequency resolution of seismic data and the dominant frequency of the Morlet wavelet. Depending on the particular frequency used, some seismic signatures representing various geological features such as channels, faults, and gas sands get enhanced (Luh 1993;Chakraborty and Okaya 1995;Kazemeini et al 2009). In this paper, we used a frequency of 15 Hz, the search angle fixed as between -p and p, and the 3D Morlet wavelet to decompose seismic data.…”

Section: A Multiattribute Approachmentioning

confidence: 99%

Multiattribute Seismic Analysis With Fractal Dimension and 2D and 3D Continuous Wavelet Transform

Saraswat

Raj

Sen

et al. 2014

SPE Reservoir Evaluation &Amp; Engineering

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The 3D post-stack seismic attributes provide an intuitive and effective way of using seismic volumes for reservoir characterization and development, and further identification of exploration targets. Some of the seismic attributes can aid in the precise prediction of the geometry and heterogeneity of subsurface geological settings. These also can provide useful information on petrophysical and lithological properties when combined with well-log information. There exist numerous seismic attributes that provide a unique interpretation on some aspects of subsurface geology. Of these, the proper demarcation of structural featuressuch as location and edges of faults and salt domes, and their throw and extent-always has been of primary concern. In this paper, we propose new multiattribute seismic algorithms by using fractal dimension and 2D/3D continuous wavelet transform (CWT). The use of higher-dimensional wavelets incorporates information from the ensemble of traces and can correlate information between neighboring traces in seismic data. The spectral decomposition that is based on the CWT aids in resolving various features of geological interest at a particular scale or frequency, which, when rendered with fractal attribute, demarcates the boundaries between those. We apply these two algorithms separately to a seismic amplitude volume and co-render output volumes together with some weights to yield a final attribute volume incorporating information from the aforementioned algorithms. We demonstrate the efficacy of these two algorithms in terms of the resolution and proper demarcation of various geological structures on real seismic data. The application of these algorithms results in better illumination and proper demarcation of various geological features such as salt domes, channels, and faults, and it illustrates how these simple tools can help to extract detailed information from seismic data.

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“…These operations allow the improvement of seismic image resolution by including high frequencies. The amplitude variation with offset uncertainties are reduced, providing more information on lithology, saturation, permeability, and pore pressure (Luh, 1993;Best et al, 1994;Carcione et al, 2003;Carcione and Picotti, 2006). Several methods have been developed for estimating the quality factor from reflection and transmission data.…”

Section: Introductionmentioning

confidence: 99%

Estimation of quality factor based on peak frequency-shift method and redatuming operator: Application in real data set

et al. 2017

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Quality factor estimation and correction are necessary to compensate the seismic energy dissipated during acoustic-/ elastic-wave propagation in the earth. In this process, known as Q-filtering in the realm of seismic processing, the main goal is to improve the resolution of the seismic signal, as well as to recover part of the energy dissipated by the anelastic attenuation. We have found a way to improve Q-factor estimation from seismic reflection data. Our methodology is based on the combination of the peak-frequency-shift (PFS) method and the redatuming operator. Our innovation is in the way we correct traveltimes when the medium consists of many layers. In other words, the correction of the traveltime table used in the PFS method is performed using the redatuming operator. This operation, performed iteratively, allows a more accurate estimation of the Q factor layer by layer. Applications to synthetic and real data (Viking Graben) reveal the feasibility of our analysis.

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Wavelet dispersion and bright spot detection

Cited by 4 publications

References 2 publications

AVO study of a gas‐hydrate deposit, offshore Costa Rica

AVO study of a gas‐hydrate deposit, offshore Costa Rica

Multiattribute Seismic Analysis With Fractal Dimension and 2D and 3D Continuous Wavelet Transform

Estimation of quality factor based on peak frequency-shift method and redatuming operator: Application in real data set

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