Migration Velocity Analysis of Seismic Data Using Common Image Cube and Green's Functions
First Claim
1. A computer implemented method of forming a measure of the velocity of travel of seismic energy through subsurface formations from emission at a seismic energy source to reception at seismic energy receivers, comprising the steps of:
- assembling in a computer seismic data received at the receivers to form an array of common image data gathers as functions of cross-correlation lags and offset over depth levels of interest in the earth;
determining in the computer, from a selected seismic event of the assembled array of common image gathers which indicates a cross-correlation lag providing a maximum seismic energy focus, an amount of seismic energy travel time required to equalize upgoing and downgoing wavefields for the selected seismic event;
repeating the step of determining an amount of seismic energy travel time for other seismic events in the assembled array of common image gathers; and
forming in the computer from the determined amounts of travel time for the seismic events in the array of common image gathers a velocity function indicating the seismic energy velocity for the depth levels of interest in the subsurface formations.
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Accused Products
Abstract
Seismic data are assembled and stored for a set of cross-correlation lag times to form an array of common image gathers over depth levels of interest. The two dimensional gathers assembled over different lag times form a three-dimensional cube of common image data. The data are analyzed to determine the travel time shift required to equalize upgoing and downgoing wavefields. Events in the common image gathers are then modeled using Green'"'"'s functions to generate a data set representing the data resulting from processing had a precise velocity model been obtainable from the seismic data. The generated data are then processed with inversion techniques to form a velocity model for seismic data analysis.
33 Citations
27 Claims
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1. A computer implemented method of forming a measure of the velocity of travel of seismic energy through subsurface formations from emission at a seismic energy source to reception at seismic energy receivers, comprising the steps of:
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assembling in a computer seismic data received at the receivers to form an array of common image data gathers as functions of cross-correlation lags and offset over depth levels of interest in the earth; determining in the computer, from a selected seismic event of the assembled array of common image gathers which indicates a cross-correlation lag providing a maximum seismic energy focus, an amount of seismic energy travel time required to equalize upgoing and downgoing wavefields for the selected seismic event; repeating the step of determining an amount of seismic energy travel time for other seismic events in the assembled array of common image gathers; and forming in the computer from the determined amounts of travel time for the seismic events in the array of common image gathers a velocity function indicating the seismic energy velocity for the depth levels of interest in the subsurface formations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A data processing system for forming a measure of the velocity of travel of seismic energy through subsurface formations from emission at a seismic energy source to reception at seismic energy receivers, the data processing system comprising:
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a data storage memory; a processor for performing the steps of; assembling in the storage memory of the data processing system seismic data received at the receivers to fox iii an array of common image data gathers as functions of cross-correlation lags and offset over depth levels of interest in the earth; determining, from a selected seismic event of the assembled array of common image gathers which indicates a cross-correlation lag providing a maximum seismic energy focus, an amount of seismic energy travel time required to equalize upgoing and downgoing wavefields for the selected seismic event; repeating the step of determining an amount of seismic energy travel time for other seismic events in the assembled array of common image gathers; and forming from the determined amounts of travel time for the seismic events in the array of common image gathers a velocity function indicating the seismic energy velocity for the depth levels of interest in the subsurface formations; and storing in the data storage memory the determined velocity functions for the seismic events indicating the seismic energy velocity for the depth levels of interest in the subsurface formations. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A data storage device having stored in a computer readable medium computer operable instructions for causing a data processing system to form a measure of the velocity of travel of seismic energy through subsurface formations from emission at a seismic energy source to reception at seismic energy receivers, the instructions stored in the data storage device causing the data processing system to perform the following steps:
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assembling in the data processing system seismic data received at the receivers to form an array of common image data gathers as functions of cross-correlation lags and offset over depth levels of interest in the earth; determining in the data processing system, from a selected seismic event of the assembled array of common image gathers which indicates a cross-correlation lag providing a maximum seismic energy focus, an amount of seismic energy travel time required to equalize upgoing and downgoing wavefields for the selected seismic event; repeating the step of determining an amount of seismic energy travel time for other seismic events in the assembled array of common image gathers; and forming in the data processing system, from the determined amounts of travel time for the seismic events in the array of common image gathers, a velocity function indicating the seismic energy velocity for the depth levels of interest in the subsurface formations. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification