System for evaluating seismic sequence lithology and property, and for evaluating risk associated with predicting potential hydrocarbon reservoir, seal, trap or source

• US 5,475,589 A
• Filed: 07/08/1993
• Issued: 12/12/1995
• Est. Priority Date: 07/08/1992
• Status: Expired due to Fees

• Current Assignee: Spiral Holding Limited
• Original Assignee: Spiral Holding Limited
• Inventors: Armitage, Kenneth R. L.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Tkacs, Stephen R.
• Application Number:
  US08/135,122
• Time in Patent Office: 887 Days
• Field of Search: 73/152, 364/421, 364/422, 364/420, 367/38, 367/59, 367/73, 367/25
• US Class Current: 702/13
• CPC Class Codes: G01V 1/30 Analysis G01V1/50 takes precedence

Abstract

A method for translating seismic time data via seismic depth data to seismic depth/lithology data, enabling reduced-risk location of hydrocarbons. Reducing dry hole risk is accomplished by introducing a new work domain which provides a several-fold increase in parameters per data point corresponding to geophysical space and associated with seismic sequence data. This work domain provides improved separation and definition and quality control of a panoply of relevant geofactors which in turn provide enhanced material information about a plurality of sedimentary rock properties. The enhanced material information is quality-controlled to be geologically possible, then further quality-controlled to be consistent with probability via quantification of burial history, depositional facies distribution and data resolution.

Claims

1. In a basin environment encompassing sedimentary rocks disposed insitu in subsurface sequences, from which well log data, including sonic data, have been obtained downhole, and from which seismic time sections and seismic velocity data derived from spectra, at discrete locations, have been obtained, a computerized method of evaluating velocity distributions and interpreting spatial distributions of said subsurface sequences, and of interpreting depositional and post-depositional and resolution errors thereof, for exploring and prospecting for subsurface hydrocarbon reservoir, seal, trap or source, said method comprising the steps of:

converting said seismic velocity data to reveal presence of seismic lithological sequences;

determining spatial velocity behavior of said seismic lithological sequences at available points of velocity control;

plotting interval velocity versus depth for said velocity control, for each sequence of said seismic lithological sequence, to determine compaction characteristics;

ascertaining apparent lithology related to said sedimentary rocks at the depth and velocity established from said determining spatial velocity behavior and plotting interval velocity versus depth steps;

constraining said sequence velocity distribution by applying adjustable filters which identify and reject evidence of velocity behavior deemed to be impossible on the basis of estimated depth, velocity, compaction and lithology, for prognosticating locations in said basin environment for exploring and prospecting for said subsurface hydrocarbon reservoir, seal, trap or source; and

storing said rejected velocity evidence and its associated location parameters in a database for use in subsequent analysis of said subsurface sequences.

2. The method recited in claim 1, wherein said available points of control in said step of determining spatial velocity behavior of said seismic lithological sequences includes well velocity control.

3. The method recited in claim 1, wherein said available points of control in said step of determining spatial velocity behavior of said seismic lithological sequences includes seismic velocity control.

4. In a basin environment encompassing sedimentary rocks disposed insitu in subsurface sequences, from which well log data, including sonic data, have been obtained downhole, and from which seismic time sections and seismic velocity data derived from spectra, at discrete locations, have been obtained, a computerized method of evaluating velocity distributions and interpreting spatial distributions of said subsurface sequences, and of interpreting depositional and post-depositional and resolution errors thereof, for exploring and prospecting for subsurface hydrocarbon reservoir, seal, trap or source, said method comprising the steps of:

converting said seismic velocity data to reveal presence of seismic lithological sequences;

constructing a work domain having parameters of time, velocity, compaction, depth and lithology, to be worked at said locations, for each sequence of said seismic lithological sequences, in conjunction with a seismic waveform;

adapting said work domain to accommodate a subdivision of said parameters into all component parts thereof, with each of said component parts associated with a change of said parameters, sufficient to cause error exploring and prospecting for aid hydrocarbon reservoir, seal, trap or source;

sensitizing said adapted work domain to a description of geophysically defined geology, as a combination of resolution error, depositional geology and burial change to geology, such that all spatial changes in said time, velocity, compaction, depth and lithology are defined on the basis of said combined changes;

spatially quantifying a majority of sequence burial changes and isolating said burial changes in filters;

removing effects of said burial changes from apparent velocity to obtain treated depositional properties and velocity error and resolution error;

constraining said treated depositional properties to act in accordance with deposition lithology, environment and form;

resolving said apparent sequence velocity distribution to cause, per reference point, two new parameters for present depth and velocity, and having normalized burial lithology expressed as corresponding normalized velocity and compaction; and

integrating all separate causes of parameter change, laterally in sequences, and vertically between sequences, to quantify the extent to which each performs in a geologically verifiable manner, for prognosticating locations in said basin environment for exploring and prospecting for said subsurface hydrocarbon reservoir, seal, trap or source.

5. The method recited in claim 4, wherein said reference point in said resolving step includes a grid point.

6. The method recited in claim 4, wherein said reference point in said resolving step includes a shot point.

7. In a basin environment encompassing sedimentary rocks disposed insitu in subsurface sequences, from which well log data, including sonic data, have been obtained downhole, and from which seismic time sections and seismic velocity data derived from spectra, at discrete locations, have been obtained, a computerized method of evaluating velocity distributions and interpreting spatial distributions of said subsurface sequences, and of interpreting depositional and post-depositional and resolution errors thereof, for exploring and prospecting for subsurface hydrocarbon reservoir, seal, trap or source, said method comprising the steps of:

converting said seismic velocity data to reveal presence of seismic lithological sequences;

accessing a compilation of geologic data using said seismic lithological sequences, such that a range of properties relevant to definition of source, seal, reservoir and migration route may be searched in said compilation to obtain a match, appropriate to classify said seismic lithological sequences derived per sequence, per grid point;

generating maps and cross sections from said classifications to display sequence behavior in terms of said source, seal, reservoir and migration route;

selecting reservoirs based upon said maps and cross sections which are sealed and structurally and stratigraphically closed and configured as traps;

determining risk for each of said classifications that said range of properties is not likely to be proven, per gridpoint, per sequence; and

assembling individual sequence, grid area material evidence from said risk determination for prognosticating locations in said basin environment for exploring and prospecting for said subsurface hydrocarbon reservoir, seal trap or source.