Abnormal transmission attenuation and its impact on seismic-fracture prediction — A physical modeling study

Luo, Min; Arihara, Norio; Wang, Shangxu; Di, Bangrang; Wei, Jianxin

doi:10.1190/1.2159048

Cited by 17 publications

(9 citation statements)

References 15 publications

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“…These findings are consistent with results of previous studies on both field and laboratory data (e.g. Clark et al 2001;Luo et al 2006;Chichinina et al 2006;Maultzsch et al 2007;Clark et al 2009) and thus, the results of the controlled scale model presented here validate the hypothesis that fracture properties can be inferred from P-wave attenuation anisotropy in seismic data.…”

Section: Discussionsupporting

confidence: 93%

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P‐wave attenuation anisotropy in fractured media: A seismic physical modelling study

Ekanem

Wei

et al. 2012

Geophysical Prospecting

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We used a laboratory scale model to study the effects aligned fractures might have on seismic wave propagation at a larger scale in real Earth imaging. Our main objective was to investigate the effect of aligned fractures on seismic P‐wave amplitude through the estimation of the induced attenuation. The physical model was constructed from a mixture of epoxy resin and silicon rubber, with inclusions designed to simulate two sets of inclined fractures at an angle of 29.2° with each other. Two‐dimensional reflection data were acquired using the pulse and transmission method in three principal directions relative to the fracture strike azimuth with the model submerged in a water tank. We used the Quality Versus Offset (QVO) method, an extension of the classical spectral ratio method for determining attenuation to estimate the induced attenuation (inverse of the seismic quality factor) from the Common Mid Point (CMP) pre‐processed gathers. The results of our analysis show that the induced P‐wave attenuation is anisotropic, with elliptical (cos2θ) variations with respect to the survey azimuth angle θ. The minor axis of the Q ellipse corresponds to the fracture normal. In this direction, i.e. across the material grain, the attenuation is a maximum. The major axis corresponds to the fracture strike direction (parallel to the material grain) where minimum attenuation occurs. These attenuation results show consistency with the azimuthal anisotropy observed in the stacking velocities in the fractured‐layer and are all consistent with the physical model, and thus provide a physical basis for using attenuation anisotropy to derive fracture properties from seismic data.

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Section: Discussionsupporting

confidence: 93%

“…Indeed, azimuthal variations in Pwave attenuation have been observed in both field and laboratory data (e.g. Clark et al 2001;Luo et al 2006;Chichinina et al 2006;Maultzsch et al 2007;Clark et al 2009) and have been linked to fracture properties. Experimental studies with laboratory scale models and numerical simulation studies (e.g.…”

Section: Introductionmentioning

confidence: 98%

P‐wave attenuation anisotropy in fractured media: A seismic physical modelling study

Ekanem

Wei

et al. 2012

Geophysical Prospecting

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“…Fracture-related anisotropic attenuation has been theoretically predicted (Hudson, Liu and Crampin 1996), observed in the laboratory (Rathore et al 1995;Luo et al 2006) and its effects have been noted in surface reflection data (Lynn 2004). The quantitative interpretation of anisotropic attenuation in terms of theoretical models remains problematic, as the underlying physics is relatively poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Modelling and analysis of attenuation anisotropy in multi‐azimuth VSP data from the Clair field

Maultzsch

Chapman

Liu

et al. 2007

Geophysical Prospecting

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A B S T R A C TAnisotropic variations in attenuation are of interest since they can give information on the fracture system and may be more amenable to measurement than absolute attenuation values. We examine methods for detecting changes in relative attenuation with azimuth from VSP data, and validate the techniques on synthetic data. Analysis of a multi-azimuth walkaway VSP data set from a fractured hydrocarbon reservoir indicates that such azimuthal variations in P-wave attenuation are observable. The effects are localized in the reservoir, and analysis allows the prediction of a fracture strike direction, which agrees with geological information. The observed effects can be modelled under reasonable assumptions, which suggests the validity of the link between the anisotropic attenuation and the fracturing. I N T R O D U C T I O NMeasurements of seismic attenuation from laboratory and field data, as well as theoretical work, indicate a link between attenuation, the presence of fractures and fluid saturation. Nevertheless, the difficulty of measuring attenuation in band-limited seismic data has impeded the routine application of attenuation-based techniques. The measurement of anisotropic attenuation is of great potential interest both because of the information it could provide about fracture systems and also because there is a suggestion that measuring directional variations of attenuation could perhaps be more robust than attempting to measure absolute values of attenuation.Fracture-related anisotropic attenuation has been theoretically predicted (Hudson, Liu and Crampin 1996), observed in the laboratory (Rathore et al. 1995;Luo et al. 2006) and its effects have been noted in surface reflection data (Lynn 2004). The quantitative interpretation of anisotropic attenuation in terms of theoretical models remains problematic, as the underlying physics is relatively poorly understood. * In previous work (Maultzsch et al. 2003), we showed that frequency dependence of shear-wave splitting could be first observed in vertical seismic profile (VSP) data and then modelled and interpreted in terms of a dynamic equivalent medium theory (Chapman 2003). The goal of this paper is to determine to what extent the concepts can also be maintained for P-wave propagation.Our theoretical expectations with respect to P-wave attenuation are outlined in Fig. 1. In addition to the expected increase of attenuation with fracture density, attenuation is predicted to increase with polar angle and azimuth away from the fracture strike. This means that the 'low attenuation azimuth' is likely to correspond to the fracture strike direction. An important point is that the magnitude of attenuation is sensitive to the fluid bulk modulus, such that, all other parameters being held constant, the attenuation is increased if the fluid bulk modulus is lowered from values typical of water to those typical of gas.In this study, we show that azimuthal variations of attenuation can be observed in a multi-azimuth walkaway VSP survey. As expected, the effec...

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“…Indeed, azimuthal variations in P-wave attenuation have been observed in both laboratory and field data (e.g. Clark et al, 2001;Luo et al, 2006;Chichinina, et al, 2006;Maultzsch et al, 2007;Clark et al, 2009, Ekanem et al, 2013, Ekanem et al, 2014 and has been linked to fracture properties. Attenuation has been observed to have higher magnitudes in fluid-saturated rocks than in dry rocks (e.g.…”

Section: Take Down Policymentioning

confidence: 98%

Seismic attenuation in fractured porous media: insights from a hybrid numerical and analytical model

Ekanem

Chapman

et al. 2015

Journal of Geophysics and Engineering

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Seismic attenuation in fluidsaturated porous rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the 'squirt-flow' mechanism. In principle the pattern of seismic attenuation recorded on an array of sensors then contains information about the medium, in terms of material heterogeneity and anisotropy, as well as material properties such as porosity, crack density and pore-fluid composition and mobility. In practice this inverse problem is challenging. Here we provide some insight into the effect of internal dissipation from analysing synthetic data produced by a hybrid numerical and analytical model for wave propagation in a fractured medium embedded in a layered geological structure. The model is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a porous, fluid-saturated material containing vertically-aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the model fractures.. Our results show that the fluid mobility, and the associated relaxation time of the fluid-pressure gradient controls the frequency range over which attenuation occurs. The induced attenuation increases with incidence angle and azimuth away from the fracture strike direction. Azimuthal variations in the induced attenuation are elliptical, allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications, including hydrocarbon exploration and production, subsurface storage of CO2 or geothermal energy extraction.

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Abnormal transmission attenuation and its impact on seismic-fracture prediction — A physical modeling study

Cited by 17 publications

References 15 publications

P‐wave attenuation anisotropy in fractured media: A seismic physical modelling study

P‐wave attenuation anisotropy in fractured media: A seismic physical modelling study

Modelling and analysis of attenuation anisotropy in multi‐azimuth VSP data from the Clair field

Seismic attenuation in fractured porous media: insights from a hybrid numerical and analytical model

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