Background velocity model building by wave-equation reflection traveltime tomography

2015 ◽  
Author(s):  
Bo Feng ◽  
Huazhong Wang ◽  
Hui Li
Keyword(s):  
Wave Equation ◽  
Model Building ◽  
Velocity Model ◽  
Traveltime Tomography ◽  
Velocity Model Building

Velocity model building by semblance maximization of modulated-shot gathers

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. U67-U73 ◽  
Author(s):  
Robert Soubaras ◽  
Bruno Gratacos
Keyword(s):  
Wave Equation ◽  
Model Building ◽  
Velocity Model ◽  
Multiscale Approach ◽  
Nonlinear Inversion ◽  
Velocity Models ◽  
Velocity Model Building ◽  
Frequency Maximum ◽  
The Cost ◽  
Starting Model

In recent years, wave-equation migration has greatly enhanced imaging in complex velocity models. However, velocity model building is still dependent on ray-theory approximations. We propose a full wave-equation methodology for velocity model building based on the nonlinear inversion of a semblance criterion with respect to the velocity field. A newly described type of migration, called the modulated-shot migration, is used to obtain the necessary gathers, which are indexed in surface angle. The semblance of these gathers, after spatial averaging, is used as the cost function. This methodology is shown to successfully image the Marmousi model and the subsalt part of the Sigsbee model, especially in terms of focusing, which is as good as with the true model, but also in terms of depthing which is enhanced compared with the initial model. Realistic constraints are used in terms of minimum frequency, maximum offset, and crudeness of the starting model. A key point in the success of this methodology is the multiscale approach wherein the iterations are started on a coarse scale, and ended at a finer scale.

Onshore wave-equation depth imaging and velocity model building

2010 ◽  
Vol 29 (11) ◽  
pp. 1386-1392 ◽  
Author(s):  
Joe Higginbotham ◽  
Morgan Brown ◽  
Cosmin Macesanu ◽  
Oscar Ramirez
Keyword(s):  
Wave Equation ◽  
Model Building ◽  
Velocity Model ◽  
Depth Imaging ◽  
Velocity Model Building

Velocity model building in complex settings: combining the strengths of Tomography and Wave‐Equation PreSDM

2008 ◽  
Author(s):  
François Audebert ◽  
Pierre Jousselin ◽  
Bertrand Duquet ◽  
Kaveh Dehghan ◽  
Yves Le Stunff
Keyword(s):  
Wave Equation ◽  
Model Building ◽  
Velocity Model ◽  
Velocity Model Building ◽  
Complex Settings

Efficient 3D velocity modeling building using joint inline and crossline plane-wave wave-equation migration velocity analyses

2020 ◽  
Author(s):  
Xuejian Liu ◽  
Lianjie Huang ◽  
Zongcai Feng ◽  
George El-kaseeh ◽  
Robert Will ◽  
...  
Keyword(s):  
Wave Equation ◽  
Plane Wave ◽  
Model Building ◽  
Velocity Model ◽  
Migration Velocity ◽  
Inversion Method ◽  
Data Interpolation ◽  
Image Domain ◽  
Velocity Model Building ◽  
3D Velocity Model

Summary Wave-equation migration velocity analysis (WEMVA) is an image-domain inversion method for velocity model building. Automatic plane-wave WEMVA (PWEMVA) calculates the moveouts of plane-wave common-image gathers (CIGs) by searching a best-fitting parabola with semblance analysis and back-projects residual CIG moveouts into wavefield wavepaths with a reflection tomographic kernel. However, 3D PWEMVA is very computationally expensive because 3D reflection tomographic inversion requires at least five 3D reverse-time migrations per iteration and stores two types of source wavefields at model boundaries. We develop a joint inline and crossline PWEMVA method for efficient 3D velocity model building. We alternatively implement the inline and crossline PWEMVAs with a constraint for each other, in which we iteratively construct the 3D velocity model update through 1D spline interpolation of 2D gradients. The inline and crossline joint inversion is practical since PWEMVA only inverts for low-wavenumber velocity perturbations along wavepaths, and the method can take less than one per cent of the computational cost of full 3D PWEMVA. To construct unaliased plane-waves for our joint inline and crossline PWEMVA, we develop a 3D data interpolation method in the frequency-wavenumber (FK) domain to recover regularly and randomly missing traces. The method minimizes the misfit on sufficiently localized data subsets with iterative optimal step-lengths and a gradient preconditioner that iteratively selects dominant dips along different azimuths. In numerical experiments, we use a 3D synthetic seismic dataset and a land 3D field seismic dataset acquired at the Farnsworth CO2-EOR [Enhanced Oil Recovery] field to demonstrate the efficacy of our velocity model building and data interpolation methods.

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