Reference velocity model estimation from prestack waveforms: Coherency optimization by simulated annealing

Geophysics ◽  
1989 ◽  
Vol 54 (8) ◽  
pp. 984-990 ◽  
Author(s):  
Evgeny Landa ◽  
Wafik Beydoun ◽  
Albert Tarantola
Keyword(s):  
Monte Carlo ◽  
Simulated Annealing ◽  
Velocity Model ◽  
Monte Carlo Step ◽  
Lateral Velocity ◽  
Seismic Waveforms ◽  
Reference Velocity ◽  
Velocity Information ◽  
Zero Offset ◽  
Annealing Method

Coherency inversion, which consists of maximizing a semblance function calculated from unstacked seismic waveforms, has the potential of estimating reliable velocity information without requiring traveltime picking on unstacked data. In this work, coherency inversion is based on the assumption that reflectors’ zero‐offset times are known and that the velocity in each layer may vary laterally. The method uses a type of Monte Carlo technique termed the generalized simulated annealing method for updating the velocity field. At each Monte Carlo step, time‐to‐depth conversion is performed. Although this procedure is slow at convergence to the global minimum, it is robust and does not depend on the initial model or topography of the objective function. Applications to both synthetic and field data demonstrate the efficiency of coherency inversion for estimating both lateral velocity variations and interface depth positions.

Nonlinear velocity inversion by a two‐step Monte Carlo method.

Geophysics ◽  
1994 ◽  
Vol 59 (4) ◽  
pp. 577-590 ◽  
Author(s):  
Side Jin ◽  
Raul Madariaga
Keyword(s):  
Monte Carlo ◽  
Velocity Model ◽  
Small Scale ◽  
Inversion Method ◽  
Nonlinear Inversion ◽  
Ray Theory ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Velocity Models ◽  
Reference Velocity

Seismic reflection data contain information on small‐scale impedance variations and a smooth reference velocity model. Given a reference velocity model, the reflectors can be obtained by linearized migration‐inversion. If the reference velocity is incorrect, the reflectors obtained by inverting different subsets of the data will be incoherent. We propose to use the coherency of these images to invert for the background velocity distribution. We have developed a two‐step iterative inversion method in which we separate the retrieval of small‐scale variations of the seismic velocity from the longer‐period reference velocity model. Given an initial background velocity model, we use a waveform misfit‐functional for the inversion of small‐scale velocity variations. For this linear step we use the linearized migration‐inversion method based on ray theory that we have recently developed with Lambaré and Virieux. The reference velocity model is then updated by a Monte Carlo inversion method. For the nonlinear inversion of the velocity background, we introduce an objective functional that measures the coherency of the short wavelength components obtained by inverting different common shot gathers at the same locations. The nonlinear functional is calculated directly in migrated data space to avoid expensive numerical forward modeling by finite differences or ray theory. Our method is somewhat similar to an iterative migration velocity analysis, but we do an automatic search for relatively large‐scale 1-D reference velocity models. We apply the nonlinear inversion method to a marine data set from the North Sea and also show that nonlinear inversion can be applied to realistic scale data sets to obtain a laterally heterogeneous velocity model with a reasonable amount of computer time.

scholarly journals 2D High-Resolution Crosswell Seismic Traveltime Tomography

2020 ◽  
Vol 25 (1) ◽  
pp. 47-53
Author(s):  
Chuan Li ◽  
JianXin Liu ◽  
Jianping Liao ◽  
Andrew Hursthouse
Keyword(s):  
High Resolution ◽  
Eastern China ◽  
Velocity Model ◽  
Well Logging ◽  
Oil Field ◽  
Traveltime Tomography ◽  
Reference Velocity ◽  
Velocity Information ◽  
High Resolution Reconstruction

This paper presents a method for combining the hybrid eikonal solver and the prior velocity information to obtain high-resolution crosswell imaging. The hybrid eikonal solver in this technique can ensure rapid and reliable forward modeling of traveltime field in an unsmoothed velocity model. We also utilize the sonic well logging curve to properly develop an initial reference velocity model, and use the sonic well logging data as the prior information for the inversion part, which can restrict the problem of non-uniqueness. The results of the numerical experiment of traveltime in multi-layer media showed that the hybrid eikonal solver was more accurate than the finite difference method. The case study of an oil field in eastern China demonstrated that our method can derive a high-resolution reconstruction of the subsurface structure by inverting the primary traveltime datasets. These results suggest that even though the eikonal equation is a high frequency approximation to the wavefield, the hybrid eikonal solver can provide an accurate traveltime field in the forward modelling step of seismic crosswell tomography, which is critical to ensure high-resolution invert imaging in a highly heterogeneous environment.

A simulation study of self-assembly of ABC star terpolymers confined between two parallel surfaces

Soft Matter ◽  
2021 ◽  
Author(s):  
Zhiyao Liu ◽  
Zheng Wang ◽  
Yuhua Yin ◽  
Run Jiang ◽  
Baohui Li
Keyword(s):  
Simulated Annealing ◽  
Phase Behavior ◽  
Phase Diagrams ◽  
Simulation Study ◽  
Self Assembly ◽  
Simulated Annealing Method ◽  
Parallel Surfaces ◽  
Annealing Method

Phase behavior of ABC star terpolymers confined between two identical parallel surfaces is systematically studied with a simulated annealing method. Several phase diagrams are constructed for systems with different bulk...

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