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A first-arrival traveltime tomography method for wave equation with reverse time migration algorithm as the engine

A technology of wave equation and reverse time migration, applied in seismic signal processing and other directions, to achieve a wide range of applications

Active Publication Date: 2018-10-09
CHINA PETROLEUM & CHEM CORP +1
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Problems solved by technology

But these methods can only approximate the range of the Fresnel zone (volume) of the band-limited seismic wave in the variable velocity medium

Method used

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  • A first-arrival traveltime tomography method for wave equation with reverse time migration algorithm as the engine
  • A first-arrival traveltime tomography method for wave equation with reverse time migration algorithm as the engine
  • A first-arrival traveltime tomography method for wave equation with reverse time migration algorithm as the engine

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Embodiment Construction

[0045] Attached below figure 1 The scheme of the present invention is further elaborated.

[0046] Step 1: Input seismic wavelet f(t), observation system, initial velocity field v(x) in depth domain, first arrival travel time T of observed seismic records obs (x r , x s ), the minimum value ε of the L2 norm of the travel time residual;

[0047] Step 2: Using the (acoustic) wave equation forward modeling method, calculate the forward simulated seismic record u in the initial velocity field cal (x r , t|x s ), to solve the following wave equation:

[0048]

[0049] Among them, x is the coordinate of any point in the underground space, and x r and x s Represent the coordinates of the geophone and source in the observation system, t represents time, and Δ represents the Laplacian operator.

[0050] Step 3: Automatically calculate the first arrival time T of the simulated seismic records cal (x r , x s );

[0051] Step 4: Calculate the first arrival travel time resi...

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Abstract

The invention discloses a wave-equation first-arrival travel-time chromatography method taking a reverse-time migration algorithm as an engine. The method comprises the following steps of inputting a seismic wavelet, observing a system, carrying out depth-domain initial speed field and observing a first-arrival travel time of a seismic record and a minimum value of a travel-time residual error norm; using an acoustic wave equation forward modeling method to calculate a forward-modeling simulated seismic record in an initial speed field and solving a wave equation; calculating primary wave arriving time of the simulated seismic record; calculating a primary wave travel time residual and determining whether a norm of the travel time residual is less than a preset precision requirement; calculating a wave equation travel time sensitivity matrix; solving a tomographic linear equation group; updating a speed model; and outputting the speed model obtained through inversion. The method has advantages that the acoustic wave equation is used so that a high inversion resolution is possessed; the method is suitable for describing a forward scattering phenomenon of a wave field; and a wave equation chromatography is used in a primary wave travel time tomography so that a high-precision background speed inversion method is acquired and a large-scale macroscopic background speed field can be inverted.

Description

technical field [0001] The invention relates to tomographic velocity inversion technology in the technical field of seismic tomography, in particular to a tomographic velocity inversion method based on two-way acoustic wave equation for first arrival travel time. Background technique [0002] According to the different data information used, seismic tomography can be mainly divided into travel time tomography, amplitude tomography and waveform tomography. Among them, the travel time chromatography method is the most robust. According to different positive processes, travel time tomography can be mainly divided into ray tomography, fat ray tomography, Fresnel body tomography and wave equation tomography. [0003] Ray tomography (Bishop et al., 1985; Tomographic determination of velocity and depth in laterally varying media, Geophysics, 50, 903-923) is based on high-frequency ray theory, and has low requirements for the accuracy of the initial model, but the inversion accurac...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V1/30
Inventor 杨淑卿单联瑜王华忠赵庆国王延光王兴谋芮拥军陈云峰王慧苗永康
Owner CHINA PETROLEUM & CHEM CORP
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