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Predicting method for longitudinal wave speed and attenuation in pore fracture medium

A technology of longitudinal wave velocity and prediction method, applied in the field of seismic rock physics, can solve the problems of not showing the characteristics of cracks and complicated calculation process

Active Publication Date: 2019-03-15
HOHAI UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] In order to solve the pore fluid flow between pores and fissures, the most classical method is to use fluid mechanics to study the pore fluid flow between pores and fissures, and many models have been proposed to explain this phenomenon (Mavko and Nur, 1975; Murphy et al., 1986; Gurevich et al., 2009 ; Carcione and Gurevich, 2011), but these models do not reflect the characteristics of cracks (crack density, crack aspect ratio and crack radius) and the calculation process is complicated

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  • Predicting method for longitudinal wave speed and attenuation in pore fracture medium

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Embodiment 1

[0081] A method for predicting the velocity and attenuation of longitudinal waves in porous and fractured media, comprising the following steps:

[0082] (1) Obtain the experimental data of ultrasonic velocity changing with pressure;

[0083] (2) Establish an equivalent medium theory that conforms to the microscopic pore structure characteristics of porous and fractured reservoirs, and combine the obtained experimental data to obtain the microscopic pore structure characteristics inside the rock;

[0084] (3) Deduce the stress-strain relationship of porous and fractured media;

[0085] (4) Deriving the equation of motion of porous and fractured media;

[0086] (5) By simulating the fracture as a coin-shaped embedded body to simulate the pore fluid flow between pores and fractures, deduce the local flow control equation of the porous and fractured medium;

[0087] (6) Using plane wave analysis to predict the longitudinal wave velocity and attenuation of porous and fractured m...

Embodiment 2

[0142] In this embodiment, a porous and fractured medium model is designed, and the Tang model, DFM model, Gassmann theory and the predicted results of the present invention are compared and analyzed, such as figure 2 shown. The basic petrophysical parameters are: the bulk modulus and shear modulus of rock particles are 37.9 and 32.6GPa respectively, and the density of rock particles is 2650; the bulk modulus of the skeleton is 4.71GPa, and the shear modulus is 4.99GPa; the volume of water Modulus 2.25GPa, density 1000kg / m 3 , viscosity 0.001Pa·s; the local porosity φ of the background phase and the embedded body 10 and φ 20 The permeability is 0.1D and 100D, the skeletal modulus is 7.6 and 0.096GPa, the fracture density is 0.2, the fracture aspect ratio is 0.002, and the fracture radius is 0.0053m. It can be seen from the figure that the P-wave velocity predicted by this note is in good agreement with Gassmann's prediction at low frequencies, and can explain the P-wave di...

Embodiment 3

[0144] In this embodiment, a porous and fractured medium model is designed to analyze the influence of fracture characteristics on the characteristics of longitudinal wave propagation. The basic petrophysical parameters are: the bulk modulus and shear modulus of rock particles are 37.9GPa and 32.6GPa respectively, and the density of rock particles is 2650kg / m 3 ; The bulk modulus of the skeleton is 4.71GPa, the shear modulus of the skeleton is 4.99GPa; the bulk modulus of water is 2.25GPa, and the density is 1000kg / m 3 , viscosity 0.001Pa·s; the local porosity φ of the background phase and the embedded body 10 and φ 20 are 0.25 and 0.32, the permeability is 0.1D and 100D, the skeleton modulus is 7.6 and 0.096GPa, image 3 The crack density is 0.2, the crack aspect ratio is 0.002, and the crack radius is 10- 6 ~0.1m, the schematic diagram of the variation of P-wave velocity and attenuation with fracture radius in seismic frequency band (10Hz), logging frequency band (1000Hz)...

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Abstract

The invention discloses a predicting method for longitudinal wave speed and attenuation in a pore fracture medium. The predicting method comprises the following steps of 1 obtaining ultrasonic speed experimental data of change along with pressure; 2, building an effective medium theory conforming to microcosmic pore structure characteristics of a pore fracture reservoir, and solving microcosmic pore structure characteristics inside rock in combination with the obtained experimental data; 3, deriving a stress strain relationship of the pore fracture medium; 4, deriving a motion equation of thepore fracture medium; 5, simulating the fractures as a coin-shaped embedding body to simulate flow of pore fluid among the pore fractures, and deriving a local area flow control equation of the pore fracture medium; 6, utilizing planar wave analysis for predicting longitudinal wave speed and attenuation of the pore fracture medium; 7, further guiding exploration and development of underground oiland gas reservoirs through the obtained longitudinal wave speed and attenuation of the pore fracture medium. According to the predicting method, the coin-shaped embedding body is utilized for simulating flow of the pore fluid among the pore fractures, and then transmission characteristics of seismic waves in the pore fracture medium are studied.

Description

technical field [0001] The invention belongs to the field of seismic rock physics, in particular to a method for predicting the velocity and attenuation of longitudinal waves in porous and fissured media. Background technique [0002] Underground rocks often have the characteristics of coexistence of pores and fissures. The existence of fissures not only affects the elastic properties of rocks, but also controls the flow of pore fluid between pores and fissures, also known as jet flow, (Müller et al., 2010; Carcione, 2014), Especially this kind of local fluid flow (referred to as local flow) is the main cause of seismic wave dispersion and attenuation in porous and fractured media. The dispersion and attenuation of seismic waves contain rich information about subsurface lithology, rock pore structure, and pore fluid (Quintal et al., 2011; Yao et al., 2015; Khalid et al., 2016). The study of the characteristics is beneficial to seismic interpretation and identification of un...

Claims

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Application Information

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IPC IPC(8): G01V1/30G01V1/28
CPCG01V1/282G01V1/306
Inventor 张琳巴晶魏颐君马汝鹏
Owner HOHAI UNIV
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