Seismic signal processing method and apparatus for generating a cube of

Abstract

A workstation computer system, and its associated method and program storage device, stores a novel software package known as 'Variance Cube'. The computer system is responsive to a plurality of seismic signals propagating through a cubic volume of an earth formation for generating a cube, representing said cubic volume of earth, where the cube includes a plurality of seismic data samples and where each seismic data sample has a corresponding 'variance value' assigned thereto. The computer system also generates one or more maps, such as a time slice map, representing one or more slices through the cube. Each map displays and is used to determine certain geologic features which exist along the corresponding slice through the cube, each map including a plurality of the variance values representing the geologic features, each such variance value being defined as the degree to which an amplitude of each seismic data sample in the cube at a particular reflection time 't' varies about an average amplitude. When the Variance Cube software is executed, the method of this invention determines the plurality of variance values by: dividing the cube into a plurality of slices, dividing each slice into a plurality of cells, calculating an average of the amplitudes of a plurality of seismic data samples in each cell on the slice, subtracting that average from each amplitude of each seismic data sample in each cell thereby producing a plurality of differences, summing the squares of the plurality of differences thereby producing a numerator, summing the squares of the plurality of amplitudes of the plurality of seismic data samples in each cell thereby producing a denominator, dividing the numerator by the denominator to thereby produce an approximate variance value which is assigned to a center seismic data sample in each cell on the time slice.