Method for exploring for hydrocarbons utilizing three dimensional modeling of thermal anomalies

• US 5,321,612 A
• Filed: 02/26/1991
• Issued: 06/14/1994
• Est. Priority Date: 02/26/1991
• Status: Expired due to Term

• Current Assignee: Swift Energy Company
• Original Assignee: Swift Energy Company
• Inventors: Stewart, Charles H.
• Primary Examiner(s): Envall, Jr., Roy N.
• Assistant Examiner(s): Hazard, J. L.
• Application Number:
  US07/661,902
• Time in Patent Office: 1,204 Days
• Field of Search: 364/420, 364/421, 364/422, 374/136, 374/137, 73/154, 250/253
• US Class Current: 702/13
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting
• CPC Class Codes: G01V 9/005 by thermal methods, e.g. after generation of heat by chemical reactions

Abstract

A method for exploring and finding a subterranean hydrocarbon reservoir by modeling of temperature and/or thermal anomalies within a geologic volume of the earth'"'"'s crust. The geologic volume is subdivided into a plurality of laterally disposed and aligned, and vertically disposed and aligned, volumetric cells. Geologic properties are assigned for each of the volumetric cells, and a normal gradient temperature is determined and generated for the geologic volume. An x, y, z temperature is assigned for each volumetric cell based on the normal gradient temperature of the geologic volume. A hypothetical hydrocarbon reservoir is disposed in the geologic volume by varying the geologic properties of some of the plurality of volumetric cells; and a true x, y, z temperature is computed for each volumetric cell caused by the hypothetical hydrocarbon reservoir. A true hydrocarbon reservoir in the geologic volume is determined from the true x, y, z temperature of each volumetric cell.

Claims

1. A computer-implemented process for exploring for hydrocarbons which utilizes temperatures determined in a geologic volume comprising the steps of:

(a) providing a geologic volume to a computer means;

(b) subdividing the geologic volume in the computer means into a plurality of laterally disposed, laterally aligned and vertically disposed, vertically aligned volumetric cells;

(c) assigning geologic properties for each of the volumetric cells;

(d) determining a normal gradient temperature for the geological volume;

(e) assigning an x, y, z temperature for each volumetric cell based on the normal gradient temperature of the geologic volume;

(f) disposing a hypothetical hydrocarbon reservoir in the geologic volume;

(g) computing with the computer means a true x, y, z temperature for each volumetric cell caused by disposing the hypothetical hydrocarbon reservoir in the geologic volume; and

(h) determining a true hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell.

2. The process of claim 1 additionally comprising determining a thermal conductivity value for each volumetric cell prior to said disposing step (f).

3. The process of claim 2 additionally comprising assigning the heat flux value to each volumetric cell prior to determining a thermal conductivity value for each volumetric cell.

4. The process of claim 3 wherein said determining a thermal conductivity value for each volumetric cell comprises determining a normal gradient temperature for each volumetric cell from the normal gradient temperature for the geologic volume, and dividing the heat flux of each volumetric cell by the normal gradient temperature for each volumetric cell.

5. The process of claim 1 wherein said disposing of a hypothetical hydrocarbon reservoir in the geologic volume comprises varying at least one geologic property of some of the plurality of volumetric cells.

6. The process of claim 5 wherein said at least one geologic property varied is selected from a group consisting of thermal conductivity, oil saturation, heat capacity of oil, gas saturation, heat capacity of gas, and mixtures thereof.

7. The process of claim 1 additionally comprising assigning a heat flux value to each volumetric cell.

8. The process of claim 1 additionally comprising determining an observed temperature for at least one volumetric cell prior to said determining step (h).

9. The process of claim 8 wherein said determining step (h) comprises comparing the true z temperature for at least one volumetric cell with said observed temperature for at least one volumetric cell.

10. In an improved computer-implemented process for exploring for hydrocarbons in a geologic volume which has been subdivided into a plurality of volumetric cells and wherein geologic properties have been assigned for each of the volumetric cells, the improvement comprising the steps of:

(a) determining a normal gradient temperature for the geologic volume;

(b) assigning an x, y, z temperature for each volumetric cell based on the normal gradient temperature of the geologic volume;

(c) disposing a hypothetical hydrocarbon reservoir in the geologic volume;

(d) with a computer means computing a true x, y, z temperature for each volumetric cell caused by disposing the hypothetical hydrocarbon reservoir in the geologic volume; and

(e) determining a true hydorcarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell.

11. A computer-implemented process for exploring for hydrocarbons comprising the steps of:

(a) providing a geologic volume to a computer means from a geographic area that is to be investigated and where thermal anomalies are to be modeled for determining if a subterranean hydrocarbon reservoir exist underneath the geographic area;

(b) subdividing the geologic volume into a plurality volumetric cells;

(c) assigning geologic properties for each of the volumetric cells;

(d) determining a gradient temperature for the geologic volume;

(e) assigning an x, y, z temperature for each volumetric cell based on the normal gradient temperature of the geologic volume;

(f) disposing a hypothetical hydrocarbon reservoir in the geologic volume;

(g) computing with the computer means a true x, y, z temperature for each volumetric cell caused by disposing the hypothetical hydrocarbon reservoir in the geological volume; and

(h) determining a subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell.

12. The process of claim 11 wherein each of said volumetric cells initially comprises geologic properties which include generally identical geologic properties with no oil and gas in any of said volumetric cells.

13. The process of claim 11 wherein said determining step (d) of said normal gradient temperature for said geologic volume comprises providing a second geologic volume having known temperature data versus depth and containing no oil and gas;

and forming a graph by plotting said known temperature data versus depth.

14. The process of claim 13 wherein said determining step (h) of a subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises comparing at least one temperature at a given depth from the plotted temperature versus cell depth curve with at least one temperature at said given depth from said normal gradient temperature of step (d) and determining if said at least one temperature from said plotted temperature versus cell depth curve equals said at least one temperature from said normal gradient temperature of step (d) within a margin of error.

15. The process of claim 14 wherein said determining step (h) of said subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises redisposing said hypothetical hydrocarbon in said geologic volume and computing a true x, y, z temperature for each volumetric cell caused by redisposing the hypothetical hydrocarbon reservoir in the geologic volume.

16. The process of claim 11 wherein said determining step (d) of said normal gradient temperature for said geologic volume comprises obtaining temperature data versus known depths for said geologic volume;

and forming a graph by plotting said temperature data against said known depths.

17. The process of claim 16 wherein said obtaining temperature data versus known depth for said geologic volume comprises measuring temperatures versus depths in the geologic volume.

18. The process of claim 17 where said measuring temperatures versus known depths in the geologic volume comprises drilling at least one well into the geologic volume and measuring a bottom hole temperature for said at least one well.

19. The process of claim 16 wherein said determining step (h) of a subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises comparing at least one temperature at a given depth from the plotted temperature versus cell depth curve with at least one temperature at said given depth from said normal gradient temperature of step (d) and determining if said at least one temperature from said plotted temperature versus cell depth curve equals said at least one temperature from said normal gradient temperature of step (d) within a margin or error.

20. The process of claim 19 wherein said determining step (h) of said subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises redisposing said hypothetical hydrocarbon in said geologic volume and computing a true x, y, z temperature for each volumetric cell caused by redisposing the hypothetical hydrocarbon reservoir in the geologic volume.

21. The process of claim 11 wherein said geologic volume comprises known thermal conductivity data versus depths in the geologic volume;

and said process additionally comprises prior to said disposing step (f) forming a graph by plotting said known thermal conductivity data versus depths in the geologic volume to determine a thermal conductivity for each of said volumetric cells.

22. The process of claim 11 additionally comprising determining a thermal conductivity value for each of said volumetric cells prior to the said disposing step (f).

23. The process of claim 22 wherein said determining of said thermal conductivity value for each of said volumetric cells prior to said disposing step (f) comprises providing a second geologic volume having known thermal conductivity data versus depths and containing no oil and gas;

and forming a graph by plotting said known thermal conductivity data versus depths.

24. The process of claim 22 wherein said determining said thermal conductivity value for each of said volumetric cells prior to said disposing step (f) comprises drilling at least one well into the geologic volume and obtaining drill cuttings from the at least one well.

25. The process of claim 11 additionally comprising after said computer step (g) forming a temperature versus cell depth curve from said true x, y, z temperature for each of said volumetric cells by plotting said true x, y, z temperature for each of said volumetric cells against cell depth of each of said volumetric cells.

26. The process of claim 25 wherein said determining step (h) of a subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises comparing at least one temperature at a given depth from said plotted temperature versus cell depth curve with at least one temperature at said given depth from said normal gradient temperature of step (d) and determining if said at least one temperature from said plotted temperature versus cell depth curve equals said at least one temperature from said normal gradient temperature of step (d) within a margin of error.

27. The process of claim 26 wherein said determining step (h) of said subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises redisposing said hypothetical hydrocarbon in said geologic volume and computing a true x, y, z temperature for each volumetric cell caused by redisposing the hypothetical hydrocarbon reservoir in the geologic volume.

28. The process of claim 11 wherein said determining step (h) of said subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell comprises redisposing said hypothetical hydrocarbon in said geologic volume and computing a true x, y, z temperature for each volumetric cell caused by redisposing the hypothetical hydrocarbon reservoir in the geological volume.

29. A computer-implemented process for collecting and processing data relating to exploring for hydrocarbons comprising the steps of:

(a) providing a geologic volume to a computer means;

(b) subdividing the geologic volume in the computer means into a plurality volumetric cells;

(c) assigning geologic properties for each of the volumetric cells;

(d) determining a normal gradient temperature for the geologic volume;

(e) assigning an x, y, z temperature for each volumetric cell based on the normal gradient temperature for the geologic volume;

(f) disposing a hypothetical hydrocarbon reservoir in the geologic volume;

(g) computing with the computer means a true x, y, z temperature for each volumetric cell caused by disposing the hypothetical hydrocarbon reservoir in the geological volume; and

(h) determining a subterranean hydrocarbon reservoir in the geologic volume from the true x, y, z temperature of each volumetric cell.