US 5,838,634 AGranted

Method of generating 3-D geologic models incorporating geologic and geophysical constraints

AssigneeExxon Production Research Company

InventorsThomas A. Jones, Sterling J. Helwick, Jr.

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Abstract

Features of subsurface earth reservoirs of interest are made available for analysis and evaluation by forming three-dimensional, geologic block models based on field data. The field data include geological observations, such as lithofacies and porosity values obtained from well data and other sources, as well as geophysical data, usually from seismic surveys. The geologic models representative of subsurface reservoirs so obtained are optimized to match as closely as feasible geologic constraints known or derived from observed geologic data. The models also conform to geophysically based constraints indicated by seismic survey data. The modeled geologic lithofacies and porosity are converted into acoustic velocity and bulk density values, which are then formulated as a seismic response which is then compared with actual seismic data. A perturbation process on lithofacies and porosity can be iteratively repeated until a representation of the reservoir is obtained which is within specified limits of accuracy or acceptability.

Claims32

Dependent claims

A method of forming a geologic model of a subsurface earth reservoir of interest based on lithofacies and porosity data obtained from wells in the reservoir and seismic traces obtained from seismic survey data, said geologic model being arranged into an assigned number of model blocks in a three-dimensional array corresponding to the reservoir, comprising the steps of:

forming a tentative geologic model by assigning obtained lithofacies and porosity values to model blocks where well data are present and by assigning estimated lithofacies and porosity values to model blocks where well data are not present;
forming synthetic seismic traces based on model block values of lithofacies and porosity, taking into account fluid saturation;
forming a statistical measure indicative of the match between the synthetic seismic traces and the obtained seismic traces;
forming measures indicative of the distribution of lithofacies and porosity values within the tentative geologic model;
comparing the measures so formed with specified criteria to determine if the degree of agreement is acceptable;
retaining the current tentative geologic model if it is determined acceptable during said step of comparing;
forming a new tentative geologic model by perturbing the lithofacies and porosity values within the current tentative geologic model if said current tentative geologic model is determined unacceptable during said step of comparing;
and
iteratively repeating said steps of forming synthetic seismic traces, forming measures, comparing measures, and retaining or perturbing until specified limits of acceptability are achieved.

6 more elements

A method of forming a geologic model of a subsurface earth reservoir of interest, said geologic model being arranged into an assigned number of blocks in a three-dimensional array corresponding to the reservoir, comprising the steps of:

obtaining geologic data from wells in the reservoir;
obtaining seismic survey data in the area of the reservoir;
forming a tentative geologic model by assigning data values to model blocks;
forming synthetic seismic traces based on the assigned model block values;
forming a statistical measure indicative of the match between the synthetic seismic traces and the obtained seismic survey data;
forming measures indicative of the distribution of model block values within the tentative geologic model;
comparing the measures so formed with specified criteria to determine if the degree of agreement is acceptable;
retaining the current tentative geologic model if it is determined acceptable during said step of comparing;
forming a new tentative geologic model by perturbing the model block values within the current tentative geologic model if said current tentative geologic model is determined unacceptable during said step of comparing;
and
iteratively repeating said steps of forming synthetic seismic traces, forming measures, comparing measures, and retaining or perturbing further until specified limits of acceptability are achieved.

8 more elements

Dependencies are inferred from the claim text.