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A method and system for inversion of fracture density in seismic strata

A technology of fracture density and fracture, which is applied in the field of seismic formation fracture fracture density inversion method and system, can solve the problems that cannot meet the quantitative evaluation of formation permeability and the calculation requirements of oil and gas reserves in fractured reservoirs

Active Publication Date: 2016-11-16
PETROCHINA CO LTD
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  • Application Information

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Problems solved by technology

However, neither the travel time difference of the split shear wave nor the ratio of the major and minor axes of the longitudinal wave ellipse can only give the relative size of the fracture density (that is, the degree of development) in the formation, which cannot meet the quantitative evaluation of the formation permeability and the oil and gas reserves of fractured reservoirs. computing requirements

Method used

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  • A method and system for inversion of fracture density in seismic strata
  • A method and system for inversion of fracture density in seismic strata
  • A method and system for inversion of fracture density in seismic strata

Examples

Experimental program
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Effect test

Embodiment 1

[0060] This example is a three-layer geological model containing faults, the model size is 1000m×800m; the grid size is: DX=DZ=10m, the fault drop is 10m, the upper and lower layers are the same, the middle layer has cracks, and the thickness of the crack layer is 30m, and the fracture direction is the same as x 1 The axes are parallel, and the model parameters are shown in Table 1:

[0061]

[0062]

[0063] Table 1

[0064] The corresponding schematic diagram of the model is as Figure 1a , Figure 1b as well as Figure 1c shown. The depth direction of fractured density rock changes as figure 2 As shown by the solid line, fissures develop near the fault, and the density of fissures gradually decreases toward both sides, as shown in image 3 shown by the solid line.

[0065] like Figure 4 As shown, it is a flow chart of a method for inversion of seismic formation fracture density in this embodiment, which includes the following steps:

[0066] Step 401, collec...

Embodiment 2

[0160] It is a five-layer geological model, and the model size and grid size are the same as those in Embodiment 1. There are cracks in the third and fourth layers, the crack density of the third layer is 0.12, and the crack direction is the same as x 1 The angle between the axes is -35°, the crack density of the fourth layer is 0.06, and the crack direction is the same as x 1 Axis angle is -75 °, the model of embodiment 2 is as Figure 7 The corresponding parameters are shown in Table 2.

[0161] layer number

Thickness (m)

p(g / cm 2 )

Vp(m / s)

Vs(m / s)

e

θ (degrees)

1

400

2400

3640

1750

0

0

2

70

2300

3157

1579

0

0

3

50

2450

3513

1887

0.12

-35

4

80

2500

3726

2053

0.06

-75

5

600

2400

3640

1750

0

0

[0162] Table 2

[0163] The model collects 30 shots of three-component seismic data, Fi...

Embodiment 3

[0169] Such as Figure 10 As shown, it is a structural diagram of a seismic formation fracture crack density inversion system of the present invention, including the following units:

[0170] A preprocessing unit 1001, configured to acquire three-component seismic data, and perform preprocessing on the three-component seismic data to obtain measured three-component shot data;

[0171] The preprocessing of the three-component seismic data includes: two-horizontal component rotation, three-component static correction, surface consistent amplitude compensation and pre-stack noise removal.

[0172] Depth-domain compressional-wave velocity and formation mass density calculation unit 1002, used to extract common center point gather data from the vertical component shot-set data in the three-component shot-set data, and perform compressional-wave velocity analysis, time-domain compressional-wave velocity calculation and compressional-wave velocity analysis. Time-depth conversion, ob...

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Abstract

The present invention provides a method and system for inversion of fracture density in seismic strata, which fully utilizes the collected seismic wave information through full waveform inversion, and automatically considers the propagation behavior of seismic waves in the ground, and can provide high-precision seismic inversion result. The invention proposes a full waveform crack density inversion method through the elastic full waveform inversion theory in the HTI medium, and realizes the quantitative prediction of the crack density of seismic underground formations.

Description

technical field [0001] The invention relates to the field of seismic exploration, in particular to a method and system for inversion of fracture density in seismic strata. Background technique [0002] Fissures and fractures are oil and gas storage spaces and percolation channels, as well as places where water and coalbed methane are enriched, stored, and migrated. Ascertaining the distribution and development of underground fractures is very important for oil and gas prediction, increasing oil and gas productivity, preventing gas explosions, roof / floor water inrush, and coalbed methane development. [0003] The parameters describing the distribution and development degree of fissures mainly include the direction of fissures and the density of fissures. At present, seismic methods for crack detection mainly include shear wave splitting method, polarization map method, longitudinal wave azimuth AVOA method and azimuth travel time method, etc. Theoretically, shear waves are ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V1/28G01V1/30
Inventor 石玉梅
Owner PETROCHINA CO LTD
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