Fracture parameter inversion for Marcellus Shale

Far, Mehdi E.; Hardage, Bob A.; Wagner, Don

doi:10.1190/geo2013-0236.1

Cited by 29 publications

(3 citation statements)

References 20 publications

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“…In that case, the fracture length can be 1 m long or 30 m long [33]. However, fracture orientations of shale can be easily obtained by field exposure or the formation microimager (FMI) log [19]. In this paper, under the assumption that the fracture width, radius, and strike were known, the WA parameters and fracture density could be directly estimated by Equation (11).…”

Section: Pp-wave Reflection Coefficient and Generalized Anisotropy Pamentioning

confidence: 99%

Seismic AVOA Inversion for Weak Anisotropy Parameters and Fracture Density in a Monoclinic Medium

Pan

2020

Applied Sciences

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In shale gas development, fracture density is an important lithologic parameter to properly characterize reservoir reconstruction, establish a fracturing scheme, and calculate porosity and permeability. The traditional methods usually assume that the fracture reservoir is one set of aligned vertical fractures, embedded in an isotropic background, and estimate some alternative parameters associated with fracture density. Thus, the low accuracy caused by this simplified model, and the intrinsic errors caused by the indirect substitution, affect the estimation of fracture density. In this paper, the fractured rock of monoclinic symmetry assumes two non-orthogonal vertical fracture sets, embedded in a transversely isotropic background. Firstly, assuming that the fracture radius, width, and orientation are known, a new form of P-wave reflection coefficient, in terms of weak anisotropy (WA) parameters and fracture density, was obtained by substituting the stiffness coefficients of vertical transverse isotropic (VTI) background, normal, and tangential fracture compliances. Then, a linear amplitude versus offset and azimuth (AVOA) inversion method, of WA parameters and fracture density, was constructed by using Bayesian theory. Tests on synthetic data showed that WA parameters, and fracture density, are stably estimated in the case of seismic data containing a moderate noise, which can provide a reliable tool in fracture prediction.

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Section: Pp-wave Reflection Coefficient and Generalized Anisotropy Pamentioning

confidence: 99%

Seismic AVOA Inversion for Weak Anisotropy Parameters and Fracture Density in a Monoclinic Medium

Pan

2020

Applied Sciences

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“…Subsurface fractures contribute to providing pathways for fluid flow and increasing the permeability of reservoirs. The key parameters of great interest for fractured reservoir exploration are the distribution and orientation of fracture systems, which play an important role in optimizing production from naturally fractured reservoirs (Sayers 2009;Far et al 2014;Den Boer and Sayers 2018).…”

Section: Introductionmentioning

confidence: 99%

Azimuthal elastic impedance-based Fourier coefficient variation with angle inversion for fracture weakness

Zhang

Pan

et al. 2020

Pet. Sci.

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Quantitative inversion of fracture weakness plays an important role in fracture prediction. Considering reservoirs with a set of vertical fractures as horizontal transversely isotropic media, the logarithmic normalized azimuthal elastic impedance (EI) is rewritten in terms of Fourier coefficients (FCs), the 90° ambiguity in the azimuth estimation of the symmetry axis is resolved by judging the sign of the second FC, and we choose the FCs with the highest sensitivity to fracture weakness and present a feasible inversion workflow for fracture weakness, which involves: (1) the inversion for azimuthal EI datasets from observed azimuthal angle gathers; (2) the prediction for the second FCs and azimuth of the symmetry axis from the estimated azimuthal EI datasets; and (3) the estimation of fracture weakness combining the extracted second FCs and azimuth of the symmetry axis iteratively, which is constrained utilizing the Cauchy sparse regularization and the low-frequency regularization in a Bayesian framework. Tests on synthetic and field data demonstrate that the 90° ambiguity in the azimuth estimation of the symmetry axis has been removed, and reliable fracture weakness can be obtained when the estimated azimuth of the symmetry axis deviates less than 30°, which can guide the prediction of fractured reservoirs.

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“…Bachrach et al (2009) expands the approximation for reflection coefficient from an HTI medium to an orthorhombic medium based on the study of Vavryčuk (1998, 2001) and uses wide-azimuthal pre-stack seismic data from the American Bakken Shale to develop AVAZ attributes inversion based on an orthorhombic medium. Far et al (2013Far et al ( , 2014 derived a complicated reflection coefficient expression of anisotropic media and inverse elastic parameters by imposing singular value decomposition on numerical simulation results based on prior information such as isotropic background. Systematic theoretical analysis is lacking regarding the relationship between orthorhombic media AVAZ attributes and fracture nature, and AVAZ attributes in orthorhombic media appear to have little practical application.…”

Section: Introductionmentioning

confidence: 99%

Fracture prediction approach for oil-bearing reservoirs based on AVAZ attributes in an orthorhombic medium

Liu

et al. 2018

Pet. Sci.

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Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fractures develop in a VTI (a transversely isotropic media with a vertical symmetry axis) background. In this case, reservoirs can be described better by using an orthorhombic medium instead of a traditional HTI (a transversely isotropic media with a horizontal symmetry axis) medium. In this paper, we focus on the fracture prediction study within an orthorhombic medium for oil-bearing reservoirs. Firstly, we simplify the reflection coefficient approximation in an orthorhombic medium. Secondly, the impact of horizontal fracturing on the reflection coefficient approximation is analyzed theoretically. Then based on that approximation, we compare and analyze the relative impact of vertical fracturing, horizontal fracturing and fluid indicative factor on traditional ellipse fitting results and the scaled B attributes. We find that scaled B attributes are more sensitive to vertical fractures, so scaled B attributes are proposed to predict vertical fractures. Finally, a test is developed to predict the fracture development intensity of an oil-bearing reservoir. The fracture development observed in cores is used to validate the study method. The findings of both theoretical analyses and practical application reveal that compared with traditional methods, this new approach has improved the prediction of fracture development intensity in oil-bearing reservoirs.

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Fracture parameter inversion for Marcellus Shale

Cited by 29 publications

References 20 publications

Seismic AVOA Inversion for Weak Anisotropy Parameters and Fracture Density in a Monoclinic Medium

Seismic AVOA Inversion for Weak Anisotropy Parameters and Fracture Density in a Monoclinic Medium

Azimuthal elastic impedance-based Fourier coefficient variation with angle inversion for fracture weakness

Fracture prediction approach for oil-bearing reservoirs based on AVAZ attributes in an orthorhombic medium

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