Non-unique seismic lithologic inversion for subterranean modeling

Apparatus for convening real seismic traces from a seismic survey composed of reflection signals which typify subterranean discontinuities, and lithologic well log data representative of the structure and texture of subterranean layers, into a model image of subterranean characteristics and structure to be displayed on a display means, said apparatus comprising:

• a computer programmed to perform method steps comprising:
• (a) determining an initial model based on said lithologic well log data and said real seismic traces, which are representative of known petrophysical parameters at an initial site;
• (b) perturbing said initial model to propose a plurality of new petrophysical parameters that bracket said known petrophysical parameters at said initial site for a plurality of forward model sites, wherein said model sites are spaced apart in an area included in said seismic survey, and wherein each forward model site is associated with a single one of said real seismic trace, which is thus designated as a characteristic seismic trace for the corresponding forward model site;
• (c) building a catalog of synthetic seismic model traces and corresponding pseudo-logs, and storing said catalog in a memory of said computer, said catalog containing a synthetic seismic model trace and a corresponding pseudo-log for each one of said plurality of new petrophysical parameters;
• (d) selecting a set of said synthetic seismic model traces having a corresponding set of said pseudo-logs from said catalog for association with each one of said characteristic seismic traces;
• (e) designating a selected one pseudo-log from said set of pseudo-logs associated with each of said characteristic traces, as a prime pseudo-log for association with each one of said characteristic seismic traces selected in step (d) to provide a plurality of prime pseudo-logs, whereby each one of said plurality of prime pseudo-logs is associated with a corresponding one of said forward model sites;
• and
• (f) using said plurality of prime pseudo-logs selected in step (e) for generating said model image of subterranean characteristics.

A program storage device, readable by a computer, tangibly embodying a program of instructions executable by said computer to perform method steps for converting real seismic traces from a seismic survey composed of reflection signals which typify subterranean discontinuities, and lithologic well log data representative of the structure and texture of subterranean layers, into a model image of subterranean characteristics and structure to be displayed on a display means, said method steps comprising:

• (a) determining an initial model based on said lithologic well log data and said real seismic traces, which are representative of known petrophysical parameters at an initial site;
• (b) perturbing said initial model to propose a plurality of new petrophysical parameters that bracket said known petrophysical parameters at said initial site for a plurality of forward model sites, wherein said forward model sites are spaced apart in an area included in said seismic survey, and wherein each forward model site is associated with a single one of said real seismic traces, which is thus designated as a characteristic seismic trace for the corresponding forward model site;
• (c) building a catalog of synthetic seismic model traces and corresponding pseudo-logs, and storing said catalog in a memory of said computer, said catalog containing a synthetic seismic model trace and a corresponding pseudo-log for each one of said plurality of new petrophysical parameters;
• (d) selecting a set of said synthetic seismic model traces having a corresponding set of said pseudo-logs from said catalog for association with each one of said characteristic seismic traces;
• (e) designating a selected one pseudo-log from said set of pseudo-logs associated with each of said characteristic traces, as a prime pseudo-log for association with each one of said characteristic seismic traces selected in step (d) to provide a plurality of prime pseudo-logs, whereby each one of said plurality of prime pseudo-logs is associated with a corresponding one of said forward model sites;
• and
• (f) using said plurality of prime pseudo-logs selected in step (e) for generating said model image of subterranean characteristics.