Method and apparatus for adaptive cross-correlation based full waveform inversion

1 . A method for performing a seismic full waveform inversion to generate a velocity model of subsurface formations of a survey region, comprising:

(a) positioning seismic data recording sensors at a plurality of locations in the survey region and positioning a well logging tool having seismic data recording sensors in a well bore in the survey region;

(b) emitting at points of incidence in the survey region to generate seismic waves, which travel through subsurface earth formations;

(c) observing the seismic waves and recording observed seismic data based on the seismic waves using the seismic data recording sensors positioned at the plurality of locations and/or disposed in the well logging tool in the well bore;

(d) transmitting the observed seismic data from the seismic data recording sensors to a computer system including one or more memories, storing the observed seismic data in the one or more memories, and storing a source wavelet and a current medium parameter model in the one or more memories;

(e) performing, by the computer system, a forward modeling operation using the source wavelet and the current medium parameter model according to a forward wave equation and obtain a forward wavefield to generate synthetic data based on the forward wave equation;

(f) processing, by the computer system, the synthetic data and the observed seismic data using a Hann window operation, respectively, to obtain a localized synthetic data and a localized seismic data;

(g) selecting, by the computer system, a traveltime difference based on a cross-correlation between the localized synthetic data and the localized seismic data;

(h) solving, by the computer system, an adjoint equation of the forward wave equation using the traveltime difference and the localized seismic data to obtain an adjoint source;

(i) generating, by the computer system, an updated medium parameter model for the seismic full waveform inversion and synthetic data using the forward modeling operation;

(j) performing operations (e) to (i) until convergence;

(k) outputting the updated velocity as a final velocity model to a display upon the convergence; and

(l) displaying an image of the final velocity model on the display of the computer system.

2 . The method of claim 1 , further comprising constructing, by the computer system, a matching filter that matches the synthetic data and the observed seismic data.

3 . The method of claim 2 , wherein the synthetic data, prior to being subject to the Hann window operation, is convolved with the matching filter.

4 . The method of claim 3 , wherein operation (i) further comprises, by the computer system, reversely propagating the adjoint source to obtain an adjoint wavefield;

calculating a gradient using the forward wavefield and the adjoint wavefield;

determining a search direction and a step length; and

updating the medium parameter model with the step length.

5 . The method of claim 1 , wherein the convergence is obtained when a value of a traveltime based misfit function is less than a predetermined value.

6 . The method of claim 1 , wherein the convergence is obtained when a number of iterations reaches a predetermined value.

7 . The method of claim 1 , wherein the medium parameter model is selected from a velocity model.

8 . The method of claim 1 , wherein the source wavelet is an Ormsby wavelet or a Ricker wavelet.

9 . The method of claim 2 , wherein the matching filter is a Wiener filter.

10 . The method of claim 4 , wherein the updating step uses an inversion method selected from a steepest-descent algorithm, a nonlinear conjugate gradient method, a Gaussian Newton's method, and a quasi-Newton's method.

11 . A system for performing a seismic full waveform inversion to generate a velocity model of subsurface formations of a survey region, the system comprising:

a plurality of seismic data recording sensors positioned in the survey region at different locations and/or a well logging tool including having seismic data recording sensors positioned in a well bore in the survey region; and

a blasting device positioned at each a point of incidence in the survey region to generate seismic waves, which travel through subsurface earth formations,

wherein:

the plurality of seismic data recording sensors and/or the seismic data recording sensors in the well logging tool positioned in the well bore are configured to sense seismic waves and record seismic data based on the seismic waves and to transmit the seismic data to a computer system including one or more memories and at least one processor,

the one or more memories are configured to store the transmitted seismic data, a source wavelet, and instructions, and

the one or more processors are configured to execute the instructions stored in the one or more memories to implement:

performing a forward modeling operation using the source wavelet and a current medium parameter model according to a forward wave equation to obtain a forward wavefield;

processing a synthetic data and an observed seismic data to Hann window operation, respectively, to obtain a localized synthetic data and a localized seismic data;

selecting a traveltime difference based on a cross-correlation between the localized synthetic data and the localized seismic data;

solving an adjoint equation of the forward wave equation using the traveltime difference and the localized seismic data to obtain an adjoint source; and

generating an updated medium parameter model for the seismic full waveform inversion and synthetic data using the forward modeling operation.