Fracture detection in Manderson Field: A 3-D AVAZ case history

Gray, David; Head, Kim

doi:10.1190/1.1438508

Cited by 48 publications

(19 citation statements)

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“…This makes characterizing the seismic properties of fractures essential in those fields of research. For instance, aligned vertical fractures can lead to an azimuthal anisotropy (Schoenberg et al 1999; Gray & Head 2000), particularly azimuthal dependence of velocity and attenuation, which is sensitive to key properties of the reservoir, such as fluid type, flow direction, porosity, permeability, etc.…”

Section: Introductionmentioning

confidence: 99%

Numerical experiments of fracture-induced velocity and attenuation anisotropy

Carcione

Picotti

Santos

2012

Geophysical Journal International

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SUMMARY Fractures are common in the Earth’s crust due to different factors, for instance, tectonic stresses and natural or artificial hydraulic fracturing caused by a pressurized fluid. A dense set of fractures behaves as an effective long‐wavelength anisotropic medium, leading to azimuthally varying velocity and attenuation of seismic waves. Effective in this case means that the predominant wavelength is much longer than the fracture spacing. Here, fractures are represented by surface discontinuities in the displacement u and particle velocity v as , where the brackets denote the discontinuity across the surface, is a fracture stiffness and is a fracture viscosity. We consider an isotropic background medium, where a set of fractures are embedded. There exists an analytical solution—with five stiffness components—for equispaced plane fractures and an homogeneous background medium. The theory predicts that the equivalent medium is transversely isotropic and viscoelastic. We then perform harmonic numerical experiments to compute the stiffness components as a function of frequency, by using a Galerkin finite‐element procedure, and obtain the complex velocities of the medium as a function of frequency and propagation direction, which provide the phase velocities, energy velocities (wavefronts) and quality factors. The algorithm is tested with the analytical solution and then used to obtain the stiffness components for general heterogeneous cases, where fractal variations of the fracture compliances and background stiffnesses are considered.

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Section: Introductionmentioning

confidence: 99%

Numerical experiments of fracture-induced velocity and attenuation anisotropy

Carcione

Picotti

Santos

2012

Geophysical Journal International

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“…Rüger (1997Rüger ( , 1998 derives the linearized PP-wave reflection coefficient of HTI media characterized by Thomsen's (1986) anisotropic parameters. Using Rüger's theory and seismic amplitude variation with offset/amplitude variation with incident angle and azimuth (AVOA/AVAZ) data, much work has been done to detect the fractures based on the inverted Thomsen's anisotropic parameters (Mallick et al 1998;Gray and Head 2000;Chen, Brown and Castagna 2005;Goodway, Varsek and Abaco 2007;Bachrach et al 2009;Downton and Roure 2015;Zhang 2018, 2019;Pan, Zhang and Yin 2019).…”

Section: Introductionmentioning

confidence: 99%

Amplitude variation with incident angle and azimuth inversion for Young's impedance, Poisson's ratio and fracture weaknesses in shale gas reservoirs

Pan

Zhang

2019

Geophysical Prospecting

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By analogy with P‐ and S‐wave impedances, the product of Young's modulus and density can be termed as Young's impedance, which indicates the rock lithology and brittleness of unconventional hydrocarbon reservoirs. Poisson's ratio is also an effective indicator of rock brittleness and fluid property of unconventional reservoirs, and fracture weaknesses indicate the fracture properties (fracturing intensity and fracture fillings) in fracture‐induced unconventional reservoirs. We aim to simultaneously estimate the Young's impedance, Poisson's ratio and fracture weaknesses from wide‐azimuth surface seismic data in a fracture‐induced shale gas reservoir, and use the horizontal transversely isotropic model to characterize the fractures. First, the linearized PP‐wave reflection coefficient in terms of Young's impedance, Poisson's ratio, density and fracture weaknesses is derived for the case of a weak‐contrast interface separating two weakly horizontal transversely isotropic media. In addition, an orthorhombic anisotropic case is also discussed in this paper. Then a Bayesian amplitude variation with incident angle and azimuth scheme with a model constraint is used to stably estimate Young's impedance, Poisson's ratio and fracture weaknesses with only PP‐wave azimuthal seismic data. The proposed approach is finally demonstrated on both synthetic and real data sets with reasonable results.

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“…Pérez et al [10] studied the practical application of Pwave AVA to the detection of fracture orientation. Gray and Head [11] studied the properties of anisotropic media based on the P-wave azimuthal anisotropy and predicted fractures in an actual oilfield. Hall and Kendall [12] applied the Pwave AVA of a submarine three-component seismic dataset to analyze natural fracture characteristics.…”

Section: Introductionmentioning

confidence: 99%

PP- and Split PS-Wave AVA Responses of Fractured Shale

Yang

2018

Mathematical Problems in Engineering

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With seismic exploration advancing to the deep Earth, the seismic response of fractured strata has currently become a hot research topic. However, characteristics of the amplitude variation with angle (AVA) of saturated fractured shale still remain unclear. Furthermore, the direct relationships between the AVA response and fracture system parameters have not received much attention. This study is aimed at analyzing the effect of fracture density on AVA responses of fractured shale. For this purpose, we propose a method for modeling saturated fractured shale and analyzing AVA responses of PP-and split PS-waves. First, we introduce Gurevich's fluid theory into the fractured-shale modeling and establish the relationship between Thomsen's weak anisotropy parameters and fracture density and fluid properties. Second, we perform forward simulation considering an isotropic overburden and a fractured stratum. The results show that differences in AVA responses of the fractured-shale model and the isotropic model increase with increasing fracture densities. At small to intermediate incidence angles, the reflection coefficients of split PS-waves increase, whereas those of PP-wave decrease. The reflection coefficients of the two models differ dramatically at incidence angles larger than 55 ∘ . Furthermore, when the fracture density is large, polarity reversal occurs only in PS2-wave AVA gathers.

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Fracture detection in Manderson Field: A 3-D AVAZ case history

Cited by 48 publications

References 0 publications

Numerical experiments of fracture-induced velocity and attenuation anisotropy

Numerical experiments of fracture-induced velocity and attenuation anisotropy

Amplitude variation with incident angle and azimuth inversion for Young's impedance, Poisson's ratio and fracture weaknesses in shale gas reservoirs

PP- and Split PS-Wave AVA Responses of Fractured Shale

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