Gravity modeling a rifted continental margin

• US 10,474,767 B2
• Filed: 01/26/2016
• Issued: 11/12/2019
• Est. Priority Date: 01/26/2016
• Status: Active Grant

• Current Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Original Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Inventors: Salem, Ahmed
• Primary Examiner(s): Dorais, Craig C
• Application Number:
  US15/007,035
• Publication Number:
  US 20170212971A1
• Time in Patent Office: 1,386 Days
• Field of Search: None
• CPC Class Codes: G01V 7/00 Measuring gravitational fields or waves; Gravimetric prospecting or detecting
• CPC Class Codes: G01V 99/00 Subject matter not provided for in other groups of this subclass

Abstract

Example computer-implemented methods, computer-readable media, and computer systems are described for performing gravity modeling. In some aspects, survey data that includes gravity data of a rifted continental margin is accessed. A value of a geometric parameter is determined, which corresponds to a desired value of a Mohorovicic Discontinuity (Moho) uplift at a specified location of the rifted continental margin. A Moho surface is determined based on a value of Moho uplift at a rift center that is determined based on the value of the geometric parameter. A top basement surface is determined based on a residual gravity data associated with the Moho surface. A crustal model of the rifted continental margin is output. The crustal model includes the Moho surface and the top basement surface of the rifted continental margin.

Claims

1. A computer-implemented gravity modeling method comprising:

accessing, by operation of a computer system, survey data that includes gravity data of a rifted continental margin;

determining, by operation of the computer system, a value of a geometric parameter that corresponds to a desired value of a Mohorovicic Discontinuity (Moho) uplift at a specified location of the rifted continental margin;

determining, by operation of the computer system, a Moho surface based on a value of Moho uplift at a rift center, the value of Moho uplift at the rift center determined based on the value of the geometric parameter;

determining, by operation of the computer system, a top basement surface based on a residual gravity data associated with the Moho surface;

outputting, by operation of the computer system, a crustal model of the rifted continental margin, the crustal model including the Moho surface and the top basement surface of the rifted continental margin; and

drilling one or more wellbores based on the Moho surface and the top basement surface of the rifted continental margin in the crustal model.

2. The method of claim 1, further comprising:

calculating a gravity response of the Moho surface; and

calculating the residual gravity response associated with the Moho surface.

3. The method of claim 1, wherein the value of Moho uplift at the rift center is determined based further on a known depth to the Moho.

4. The method of claim 1, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidate Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

calculating a plurality of candidate depths to the top basement for the plurality of candidate Moho surfaces; and

identifying a best candidate Moho surface based on a misfit between the plurality of candidate depths of the top basement and a known depth to the top basement.

5. The method of claim 1, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidates Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

for each of the plurality of candidate Moho surfaces,

determining a candidate gravity response of the candidate Moho surface;

determining a candidate residual gravity data associated with the candidate Moho surface;

calculating a correlation between the gravity response of the candidate Moho surface and the candidate residual gravity data associated with the candidate Moho surface; and

identifying a best candidate Moho surface among the plurality of candidate Moho surfaces based on respective correlation coefficients of the plurality of candidate Moho surfaces.

6. The method of claim 1, wherein determining a value of a geometric parameter comprises determining the value of the geometric parameter in an iterative manner.

7. The method of claim 1, wherein the specified location of the rifted continental margin is a continental oceanic boundary or the rift center of the rifted continental margin.

8. The method of claim 1, wherein the depth to Moho surface, denoted as h_m, is determined according to:

9. A non-transitory computer-readable medium storing instructions executable by a computer system to perform operations comprising:

accessing, by operation of the computer system, survey data that includes gravity data of a rifted continental margin;

determining, by operation of the computer system, a value of a geometric parameter that corresponds to a desired value of a Mohorovicic Discontinuity (Moho) uplift at a specified location of the rifted continental margin;

determining, by operation of the computer system, a Moho surface based on a value of Moho uplift at a rift center, the value of Moho uplift at the rift center determined based on the value of the geometric parameter;

determining, by operation of the computer system, a top basement surface based on a residual gravity data associated with the Moho surface;

outputting, by operation of the computer system, a crustal model of the rifted continental margin, the crustal model including the Moho surface and the top basement surface of the rifted continental margin; and

drilling one or more wellbores based on the Moho surface and the top basement surface of the rifted continental margin in the crustal model.

10. The computer-readable medium of claim 9, the operations further comprising:

calculating a gravity response of the Moho surface; and

calculating the residual gravity response associated with the Moho surface.

11. The computer-readable medium of claim 9, wherein the value of Moho uplift at the rift center is determined based further on a known depth to the Moho.

12. The computer-readable medium of claim 9, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidate Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

calculating a plurality of candidate depths to the top basement for the plurality of candidate Moho surfaces; and

identifying a best candidate Moho surface based on a misfit between the plurality of candidate depths of the top basement and a known depth to the top basement.

13. The computer-readable medium of claim 9, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidates Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

for each of the plurality of candidate Moho surfaces,

determining a candidate gravity response of the candidate Moho surface;

determining a candidate residual gravity data associated with the candidate Moho surface;

calculating a correlation between the gravity response of the candidate Moho surface and the candidate residual gravity data associated with the candidate Moho surface; and

identifying a best candidate Moho surface among the plurality of candidate Moho surfaces based on respective correlation coefficients of the plurality of candidate Moho surfaces.

14. The computer-readable medium of claim 9, wherein determining a value of a geometric parameter comprises determining the value of the geometric parameter in an iterative manner.

15. The computer-readable medium of claim 9, wherein the specified location of the rifted continental margin is a continental oceanic boundary or the rift center of the rifted continental margin.

16. The computer-readable medium of claim 9, wherein the depth to Moho surface, denoted as h_m, is determined according to:

17. A system comprising one or more computers that include:

memory operable to store survey data; and

data processing apparatus operable to;

access survey data that includes gravity data of a rifted continental margin;

determine a value of a geometric parameter that corresponds to a desired value of a Mohorovicic Discontinuity (Moho) uplift at a specified location of the rifted continental margin;

determine a Moho surface based on a value of Moho uplift at a rift center, the value of Moho uplift at the rift center determined based on the value of the geometric parameter;

determine a top basement surface based on a residual gravity data associated with the Moho surface;

output a crustal model of the rifted continental margin, the crustal model including the Moho surface and the top basement surface of the rifted continental margin; and

drill one or more wellbores based on the Moho surface and the top basement surface of the rifted continental margin in the crustal model.

18. The system of claim 17, wherein the value of Moho uplift at the rift center is determined based further on a known depth to the Moho.

19. The system of claim 17, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidate Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

calculating a plurality of candidate depths to the top basement for the plurality of candidate Moho surfaces; and

identifying a best candidate Moho surface based on a misfit between the plurality of candidate depths of the top basement and a known depth to the top basement.

20. The system of claim 17, wherein determining a Moho surface based on a value of Moho uplift at a rift center comprises:

determining a plurality of candidates Moho surfaces based on a plurality of candidate values of Moho uplift at the rift center;

for each of the plurality of candidate Moho surfaces,

determining a candidate gravity response of the candidate Moho surface;

determining a candidate residual gravity data associated with the candidate Moho surface;

calculating a correlation between the gravity response of the candidate Moho surface and the candidate residual gravity data associated with the candidate Moho surface; and

identifying a best candidate Moho surface among the plurality of candidate Moho surfaces based on respective correlation coefficients of the plurality of candidate Moho surfaces.