Method for interpretation of seismic records to yield indicating of the lithology of gas-bearing and capping strata

Claim 1

A method for determining lithology of gas-bearing strata in the earth using high-intensity amplitude events in seismic records, comprising the steps of: (a) generating seismic data, including a record of signals from acoustic discontinuities associated with said strata of interest by positioning and employing an array of sources and detectors such that centerpoints between selected pairs of sources and detectors form a series of centerpoints along a line of survey, said recorded signals being the output of said detectors; (b) by means of automated processing means, statically and dynamically correcting said recorded signals to form corrected traces whereby each of said corrected traces is associated with a centerpoint horizontally midway between a source-detector pair from which said each corrected trace was originally derived; (c) by means of automated processing means, indexing said corrected traces in two dimensions whereby each of said corrected traces is identified in its relationship to neighboring traces on the basis of progressive changes in horizontal offset value versus progressive changes in common centerpoint location; (d) displaying a series of said traces of step (c) on a side-by-side basis as a function of progressively changing horizontal offset values, said displayed traces all being associated with at least the same general common group of centerpoints whereby progressive change in a high-intensity amplitude event from trace to trace of said displayed traces as a function of progressive change in horizontal offset value, more likely than not relates to reflections from acoustic discontinuities associated with strata containing gaseous hydrocarbons; and (e) determining lithologic character of the strata containing the gaseous hydrocarbons based on the direction of the progressive change in the amplitude event as a function of horizontal offset.

Claim 2

A method for determining lithology of gas-bearing strata in the earth using high-intensity amplitude events in seismic records, comprising the steps of: (a) generating seismic data, including a record of signals from acoustic discontinuities associated with said strata of interest by positioning and employing an array of sources and detectors such that centerpoints between selected pairs of sources and detectors form a series of centerpoints along a line of survey, said recorded signals being the output of said detectors; (b) by means of automated processing means, statically and dynamically correcting said recorded signals to form corrected traces whereby each of said corrected traces is associated with a centerpoint horizontally midway between a source-detector pair from which said each corrected trace was originally derived; (c) by means of automated processing means, indexing said corrected traces in two dimensions whereby each of said corrected traces is identified in its relationship to neighboring traces on the basis of progressive changes in horizontal offset value versus progressive changes in common centerpoint location; (d) displaying a series of said traces of step (c) on a side-by-side basis as a function of progressively changing horizontal offset values, said displayed traces all being associated with at least the same general common group of centerpoints whereby progressive change in a high-intensity amplitude event from trace to trace of said displayed traces as a function of progressive change in horizontal offset value, more likely than not relates to reflections from acoustic discontinuities associated with strata containing gaseous hydrocarbons; and (e) determining lithologic character of the strata containing the gaseous hydrocarbons based on the direction of the progressive change in the amplitude event as a function of horizontal offset.

Claim 9

A method for converting an original multitrace seismic record into an improved section having increased capability as to the lithologic nature of high-intensity amplitude events related to reflections from subsurface strata containing gaseous hydrocarbons, said improved section being composed of a plurality of amplitude-versus-horizontal offset-and-time traces, said original record consisting of a plurality of multitrace seismic traces of amplitude-versus-horizontal coordinate-and-time, each of said traces constituting energy derived in association with a particular source-detector pair of known horizontal offset and of known centerpoint location, and representing, in part, event reflections from said subsurface strata, said conversion comprising the steps of: (a) classifying said original traces on the basis of common but progressively changing horizontal offset values and common but progressively changing common centerpoint locations, whereby each trace is identified by a centerpoint location common to at least another trace and a known horizontal offset value; (b) displaying at least said each trace and said another trace associated with said common centerpoint location, as a function of progressively changing horizontal offset values to form at least a segment of said improved section whereby progressive change in a high-intensity amplitude event common to said each trace and said another trace identified as a function of progressive change in horizontal offset, relates to reflections from acoustic discontinuities associated with strata containing gaseous hydrocarbons; and (c) determining lithologic character of the strata containing the gaseous hydrocarbons based on the direction of progressive change in the amplitude event common to said traces.

Claim 10

A method for converting an original multitrace seismic record into an improved section having increased capability as to the lithologic nature of high-intensity amplitude events related to reflections from subsurface strata containing gaseous hydrocarbons, said improved section being composed of a plurality of amplitude-versus-horizontal offset-and-time traces, said original record consisting of a plurality of multitrace seismic traces of amplitude-versus-horizontal coordinate-and-time, each of said traces constituting energy derived in association with a particular source-detector pair of known horizontal offset and of known centerpoint location, and representing, in part, event reflections from said subsurface strata, said conversion comprising the steps of: (a) classifying said original traces on the basis of common but progressively changing horizontal offset values and common but progressively changing common centerpoint locations, whereby each trace is identified by a centerpoint location common to at least another trace and a known horizontal offset value; (b) displaying at least said each trace and said another trace associated with said common centerpoint location, as a function of progressively changing horizontal offset values to form at least a segment of said improved section whereby progressive change in a high-intensity amplitude event common to said each trace and said another trace identified as a function of progressive change in horizontal offset, relates to reflections from acoustic discontinuities associated with strata containing gaseous hydrocarbons; and (c) determining lithologic character of the strata containing the gaseous hydrocarbons based on the direction of progressive change in the amplitude event common to said traces.