Estimation of fracture parameters from reflection seismic data—Part I: HTI model due to a single fracture set

Bakulin, Andrey; Grechka, Vladimir; Tsvankin, Ilya

doi:10.1190/1.1444863

Cited by 509 publications

(230 citation statements)

References 33 publications

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“…Authors [12][13][14] use third-order elasticity theory to characterize 3D stress dependence elasticity and anisotropy. Authors [15][16][17] introduce nonlinear models consistent with empirically derived phenomenological equations [18]. Our interest in the discrete and analytic models described earlier (and in more detail below) is based on seeking formulations described using few and intuitive effective microstructural model parameters that can be calibrated with available data (e.g., ultrasonic core data).…”

Section: Rock Physics Modelmentioning

confidence: 99%

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Angus

Fisher²,

Verdon³

2012

IJG

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Stress dependent rock physics models are being used more routinely to link mechanical deformation and stress perturbations to changes in seismic velocities and seismic anisotropy. In this paper, we invert for the effective non-linear microstructural parameters of 69 dry and saturated sandstone core samples. We evaluate the results in terms of the model input parameters of two non-linear rock physics models: A discrete and an analytic microstructural stress-dependent formulation. The results for the analytic model suggest that the global trend of the initial crack density is lower and initial aspect ratio is larger for the saturated samples compared to the corresponding dry samples. The initial aspect ratios for both the dry and saturated samples are tightly clustered between 0.0002 and 0.001, whereas the initial crack densities show more scatter. The results for the discrete model show higher crack densities for the saturated samples when compared to the corresponding dry samples. With increasing confining stress the crack densities decreases to almost identical values for both the dry and saturated samples. A key result of this paper is that there appears to be a stress dependence of the compliance ratio N T B B within many of the samples, possibly related to changing microcrack geometry with increasing confining stress. Furthermore, although the compliance ratio N T B B for dry samples shows a diffuse distribution between 0.4 and 2.0, for saturated samples the distribution is very tightly clustered around 0.5. As confining stresses increase the compliance ratio distributions for the dry and saturated samples become more diffuse but still noticeably different. This result is significant because it reaffirms previous observations that the compliance ratio can be used as an indicator of fluid content within cracks and fractures. From a practical perspective, an overarching purpose of this paper is to investigate the range of input parameters of the microstructural models under both dry and saturated conditions to improve prediction of stress dependent seismic velocity and anisotropy observed in time-lapse seismic data due to hydro-mechanical effects related to fluid production and injection.

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Section: Rock Physics Modelmentioning

confidence: 99%

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Angus

Fisher²,

Verdon³

2012

IJG

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“…Chichinina et al (2015) analyse the limitations of Schoenberg & Sayers (1995) LS model and find that their model is not generally adequate for real rocks. Chichinina et al (2015) note that the LS model is only valid for two conditions: (1) when Z N = 0 (i.e., case of fluid-filled fractures) or (2) when the scalar crack Z N /Z T = 1 is assumed (i.e., Bakulin et al, 2000). Hildyard (2001) observed that the LS model was only accurate for high-stiffness fractures and became increasingly inaccurate as the stiffness decreased, which is consistent with the first condition Z N = 0.…”

Section: Discussionmentioning

confidence: 99%

When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

Yousef

Angus

2016

Earth and Planetary Science Letters

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Fractures are pervasive features within the Earth's crust and have a significant influence on the multi-physical response of the subsurface. The presence of coherent fracture sets often leads to observable seismic anisotropy enabling seismic techniques to remotely locate and characterise fracture systems. In this study, we confirm the general scale-dependence of seismic anisotropy and provide new results specific to shear-wave splitting (SWS). We find that SWS develops under conditions when the ratio of wavelength to fracture size (λ S /d) is greater than 3, where Rayleigh scattering from coherent fractures leads to an effective anisotropy such that effective medium model (EMM) theory is qualitatively valid. When 1 < λ S /d < 3 there is a transition from Rayleigh to Mie scattering, where no effective anisotropy develops and hence the SWS measurements are unstable. When λ S /d < 1 we observe geometric scattering and begin to see behaviour similar to transverse isotropy. We find that seismic anisotropy is more sensitive to fracture density than fracture compliance ratio. More importantly, we observe that the transition from scattering to an effective anisotropic regime occurs over a propagation distance between 1 to 2 wavelengths depending on the fracture density and compliance ratio. The existence of a transition zone means that inversion of seismic anisotropy parameters based on EMM will be fundamentally biased. More importantly, we observe that linear slip EMM commonly used in inverting fracture properties is inconsistent with our results and leads to errors of approximately 400% in fracture spacing (equivalent to fracture density) and 60% in fracture compliance. Although EMM representations can yield reliable estimates of fracture orientation and spatial location, our results show that EMM representations will systematically fail in providing quantitatively accurate estimates of other physical fracture properties, such as fracture density and compliance. Thus more robust and accurate quantitative estimates of in situ fracture properties will require improvements to effective medium models as well as the incorporation of full-waveform inversion techniques.

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“…This model uses physically intuitive relations between stress and discontinuity in displacement across the fracture plane, and is formulated in terms of excess compliances (or weaknesses) of the material caused by the presence of fractures. It requires no assumptions about the microstructure or microgeometry of the fractures (Bakulin et al, 2000).…”

Section: Anisotropic Rock Property Prediction Workflowmentioning

confidence: 99%

Evaluating the Impact of Fracture-Induced Anisotropy on Rock Property Estimates Made from Seismic Data

Gurevich¹,

Hansen²

2003

The 7th International Symposium on Recent Advances in Exploration Geophysics (RAEG 2003)

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Naturally fractured reservoirs have attracted increasing interest in exploration and production geophysics in recent years. The presence of fractures can affect the AVO response of a reservoir. In this paper we analyse this effect of fractures in a porous reservoir on seismic data, and estimate the errors in the estimation of reservoir properties due to ignoring the presence of these fractures.The effect of fractures on elastic properties of a porous rock is studied using the model of fractures as linear-slip interfaces in an isotropic porous background. The effect of fluid on the elastic properties of this medium is modelled using equations of anisotropic poroelasticity. This yields explicit analytical expressions for the elastic properties of the fractured porous medium saturated with a given fluid.We use this theory to model the seismic response of a reservoir with vertical fractures. We then invert this response for reservoir properties (porosity, net-to-gross) using a workflow based on the above theory, and compare the predictions with the results of the standard industry workflow based on the isotropic Gassmann equation. The comparison yields an estimate of the potential error in the prediction of rock properties using an isotropic workflow for a fractured reservoir. These errors can be as large as ±3% in predicted porosity, and ±40% in predicted netto-gross.

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Estimation of fracture parameters from reflection seismic data—Part I: HTI model due to a single fracture set

Cited by 509 publications

References 33 publications

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

Evaluating the Impact of Fracture-Induced Anisotropy on Rock Property Estimates Made from Seismic Data

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