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Orthotropic dielectric fluid factor and fracture parameter inversion method.

An orthotropic, medium-fluid technology, applied in the field of physical inversion, can solve problems such as fluid and fracture property uncertainties

Inactive Publication Date: 2020-01-14
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, these fracture fluid indicators described above exhibit a coupling effect between fracture density and fluid filling, leading to uncertainties in fluid and fracture properties in this fracture background medium

Method used

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  • Orthotropic dielectric fluid factor and fracture parameter inversion method.
  • Orthotropic dielectric fluid factor and fracture parameter inversion method.
  • Orthotropic dielectric fluid factor and fracture parameter inversion method.

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Embodiment 1

[0129] Referring to Figures 1 to 16, an inversion method for fluid factors and fracture parameters in orthotropic media includes the following steps:

[0130]Step 1: Use the vertical and transverse isotropic medium in the dry rock background, and derive the stiffness matrix of the orthosymmetric anisotropic fractured medium according to the fracture weakness;

[0131] Horizontal thin layers with vertical fractures can be regarded as long-wavelength equivalent orthotropic media. When it is assumed that the dry rock skeleton is a porous rock in the VTI background composed of a set of horizontal fractures perpendicular to the x-axis, the dry rock stiffness tensor is as follows:

[0132]

[0133] 0 represents a 3×3 zero matrix, and Expressed as follows:

[0134]

[0135]

[0136] Here, δ N ,δ V and δ H is the dimensionless fracture weakness in different directions; δ N Expressed as normal weakness, related to the fluid filling; δ V and δ H denoted as vertical a...

Embodiment 2

[0205] Taking the well logging data in the gas-bearing fractured porous background as an example, the proposed Bayesian-EIVOAz inversion method for fluid and fracture separation is verified. Anisotropic logging information is first estimated using a petrophysical model. The process of constructing the rock physics model of the orthosymmetric fractured porous background medium, such as Figure 5 As shown, it is used to estimate the anisotropy logging information. Figure 6a , 6b and 6c show synthetic azimuthal seismic data. The six azimuth angles are 0°, 30°, 60°, 90°, 120° and 150° respectively. Then, a Bayesian-EIVOAz inversion that separates fluid factors and fracture properties is implemented. The original, initial and inversion logs of the model parameters are shown in Fig. 7, respectively. From the inversion results, it can be seen that even though the initial model is relatively smooth, the model parameters are reasonably estimated. Random Gaussian noise is added to ...

Embodiment 3

[0207] Referring to Fig. 13 to Fig. 16, this embodiment takes the actual data of the Sichuan Basin as an example to demonstrate the method of estimating fluid and fracture attributes using the Bayesian-EIVOAz method. The input seismic data of four azimuths are 22.5°, 67.5°, 112.5° and 157.5° respectively. The Bayesian-EIVOAz inversion is realized using partial angle stacked seismic sections shown in Fig. 11. The average incidence angles of near, medium and far angle stacks are 5° (range 0°-10°), 15° (range 10°-20°) and 25° (ranging from 20°-30°). The azimuthal elastic impedance profile obtained by inversion is shown in Fig. 12.

[0208] The estimated separation fluid factors and fracture parameters are shown in Figs. 13, 14 and 15. The right well with white curve and ellipse is used as the initial model, and the left well with gas-bearing response is used as the verification of the initial model. It is easy to find that the estimated values ​​of fluid parameters and fractur...

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Abstract

The invention provides an orthotropic dielectric fluid factor and fracture parameter inversion method. The method comprises the following steps: deducing a rigidity matrix of an ortho-symmetric anisotropic fracture medium by using a vertical transverse isotropic medium under a dry rock background according to fracture weakness; with utilization of hypotheses of weak anisotropy and small fracture weakness, deducing a new expression of weak anisotropy approximate rigidity of a saturated fluid rock in an orthogonal medium by combining an anisotropy Gassmann equation; acquiring a PP wave linearized reflection coefficient for fluid and fracture parameter decoupling in the orthogonally symmetrical weak anisotropic medium by combining stiffness disturbance and scattering theories; and with logging information as prior information, realizing elastic impedance pre-stack inversion changing with offset and azimuth angle by using a partial incident angle stacked by azimuth seismic data under Bayesian framework. According to the invention, Reliable results can be provided for fluid identification and fracture characterization; and technical supports are provided for seismic wave propagation research, oil and gas development and seismic disaster prevention.

Description

technical field [0001] The invention relates to the technical field of physical inversion, in particular to an inversion method for fluid factors and fracture parameters in an orthotropic medium. Background technique [0002] Distinguishing fluid and fracture properties is key to reservoir exploration and production, and information on "sweet spots" of high fracture density properties is needed to locate wells to maximize production. For subsurface fracture detection, azimuth seismic reflection amplitudes are widely used to estimate fracture properties. Fluid indicators estimated directly from seismic reflection data are one of the hotspots used in fluid identification. For fracture-induced anisotropy, fracture properties are assessed using dimensionless fracture compliance or weakness, where normal compliance or weakness exhibits a significant dependence on fluid filling, while tangential compliance or weakness does not vary with Fluid content varies. Therefore, the rati...

Claims

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Application Information

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IPC IPC(8): G01V1/30G01V1/28
CPCG01V1/282G01V1/306G01V1/307G01V2210/586G01V2210/6226G01V2210/626G01V2210/63
Inventor 潘新朋柳卓柳建新张大洲崔益安
Owner CENT SOUTH UNIV
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