Method for tomographically laterally varying seismic data velocity estimation

Claim 1

A method of seismic energy processing to determine estimated velocities using a diffraction tomographic technique, comprising the steps of: inputting pre-processed and dynamically corrected seismic section data as derived for selected sources and receivers along a line of survey over an inhomogeneous earth medium; determining true travel times between each source and each receiver for specific reflectors of the section data; estimating travel times and sensitivity matrix parameters with respect to model parameters of the section data for source-reflector-receiver rays of an initial model; receiving the true travel times and the estimated model travel times and determining ray-based parameter corrections by designating the earth medium as a predetermined array of cells of selected size and determining energy velocities at respective cell corners, and energy reflectors in terms of cell depth; updating the model parameters as a weighted combination of the ray-based corrections; iterating the steps of determining ray-based parameter corrections and updating the model parameters; testing the updated travel time parameters to determine if convergence criteria are satisfied such as when there is no appreciable decrease in travel time error; and outputting the estimated velocities relative to the reflector position for the section data.

Claim 2

A method of seismic energy processing to determine estimated velocities using a diffraction tomographic technique, comprising the steps of: inputting pre-processed and dynamically corrected seismic section data as derived for selected sources and receivers along a line of survey over an inhomogeneous earth medium; determining true travel times between each source and each receiver for specific reflectors of the section data; estimating travel times and sensitivity matrix parameters with respect to model parameters of the section data for source-reflector-receiver rays of an initial model; receiving the true travel times and the estimated model travel times and determining ray-based parameter corrections by designating the earth medium as a predetermined array of cells of selected size and determining energy velocities at respective cell corners, and energy reflectors in terms of cell depth; updating the model parameters as a weighted combination of the ray-based corrections; iterating the steps of determining ray-based parameter corrections and updating the model parameters; testing the updated travel time parameters to determine if convergence criteria are satisfied such as when there is no appreciable decrease in travel time error; and outputting the estimated velocities relative to the reflector position for the section data.

Claim 10

A method for processing seismic data to effect tomographic parameter estimation related to laterally varying seismic energy velocities, comprising: inputting pre-processed and dynamically corrected seismic section data as derived for selected offset sources and receivers along a designated line of survey; aligning the seismic section data with a grid array of two-dimensional cells of predetermined coordinate size; writing to file for each offset each of the derivatives of travel time with respect to velocities at cell corners, the derivatives of travel time with respect to reflector position parameters, the number of rays visiting each cell corner, the number of rays visiting each reflector position parameter, the travel time estimate of each ray; read from file for ray tracing each of model parameters consisting of the derivatives of travel time for velocities at cell corners, the derivatives of travel time for reflector position parameters, the number of rays visiting each cell corner, the number of rays visiting each reflector position parameter, and the travel time estimate of each ray; initialize the iteration count; initialize the sum of corrections for the velocities at cell corners, and the sum of corrections for the reflector position parameters; determine the sum of corrections for all rays for each velocity and reflector position parameter; normalize all summed correction values; compute estimates of the ray-based quantities α v and α p ; query data to determine extent of convergence; and outputting the data result when predetermined convergence is attained.

Claim 11

A method for processing seismic data to effect tomographic parameter estimation related to laterally varying seismic energy velocities, comprising: inputting pre-processed and dynamically corrected seismic section data as derived for selected offset sources and receivers along a designated line of survey; aligning the seismic section data with a grid array of two-dimensional cells of predetermined coordinate size; writing to file for each offset each of the derivatives of travel time with respect to velocities at cell corners, the derivatives of travel time with respect to reflector position parameters, the number of rays visiting each cell corner, the number of rays visiting each reflector position parameter, the travel time estimate of each ray; read from file for ray tracing each of model parameters consisting of the derivatives of travel time for velocities at cell corners, the derivatives of travel time for reflector position parameters, the number of rays visiting each cell corner, the number of rays visiting each reflector position parameter, and the travel time estimate of each ray; initialize the iteration count; initialize the sum of corrections for the velocities at cell corners, and the sum of corrections for the reflector position parameters; determine the sum of corrections for all rays for each velocity and reflector position parameter; normalize all summed correction values; compute estimates of the ray-based quantities α v and α p ; query data to determine extent of convergence; and outputting the data result when predetermined convergence is attained.