Non-unique seismic lithologic inversion for subterranean modeling
First Claim
1. A computer implemented method 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 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.
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Abstract
A method of modeling subsurface reservoir conditions deals with non-uniqueness of seismic reflection signals with respect to reservoir conditions by proposing and then comparing both seismic and lithologic data for forward model sites to select the most likely model for each site. Forward modeling techniques are used to build a synthetic seismic trace catalog, which includes a range of corresponding pseudo-logs for reservoir characteristics that could reasonably exist within a defined region. Then each synthetic seismic trace in the catalog is compared against every real seismic trace, and a number (e.g., 10 to 50) of synthetic traces is selected for association with each real trace that best match the real trace. Finally, the pseudo-logs corresponding to the number of selected synthetic seismic traces for each forward model site are compared to the pseudo-logs selected for adjacent sites to select the most lithologically coherent pseudo-log at each site for use in generating a model display of reservoir characteristics.
69 Citations
22 Claims
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1. A computer implemented method 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 comprising:
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(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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. 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. - View Dependent Claims (13, 14, 15, 16, 17)
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18. 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:
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(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. - View Dependent Claims (19, 20, 21, 22)
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Specification