Method of real time subsurface imaging using electromagnetic data acquired from moving platforms

• US 9,322,910 B2
• Filed: 06/04/2012
• Issued: 04/26/2016
• Est. Priority Date: 07/15/2011
• Status: Active Grant

• Current Assignee: TechnoImaging, LLC
• Original Assignee: TechnoImaging, LLC
• Inventors: Zhdanov, Michael S., Wilson, Glenn A., Cox, Leif H.
• Primary Examiner(s): Barbee, Manuel L
• Application Number:
  US13/488,256
• Publication Number:
  US 20130018585A1
• Time in Patent Office: 1,422 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01V 3/083 Controlled source electromagnetic [CSEM] surveying
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G01V 3/16 specially adapted for use from aircraft G01V3/165 - G01V3/175 take precedence

Abstract

A method for the real time volume imaging of geological structures and/or man-made objects having electrical conductivity is described, using electromagnetic (EM) sources and/or EM sensors mounted from at least one moving platform. The EM sources may include natural EM sources and/or man-made inductive sources and/or man-made galvanic sources. The EM sensors may measure at least one component of the EM field at the at least one sensor position. The EM fields measured for each combination of EM source and EM sensor may be volume imaged in real time using a moving sensitivity domain that captures the finite spatial sensitivity of each combination of EM sources and EM sensors. At least one desired property, such as conductivity, dielectric permittivity and/or induced polarization parameters, may be derived from the volume image, providing a reconstruction or classification of the physical properties of the geological structures and/or man-made objects.

Claims

1. A method for real time volume imaging of electrical conductivity of an examined medium from electromagnetic (EM) data measured from at least one moving platform, the method comprising:

a. placing at least one physical EM source and/or physical EM sensor in at least one position on at least one moving platform and moving the moving platform from the start of a survey up to a given time moment t;

b. measuring while the moving platform is moving at least one component of electric and/or magnetic field data with the at least one physical EM sensor in at least one receiving position on the moving platform along at least one survey line by the at least one moving platform from the start of the survey up to the given time moment t;

c. computing predicted at least one component of EM data from the start of the survey up to the given time moment t by use of an initial 3D electrical conductivity model that is based on known information regarding the examined medium;

d. calculating a temporal sensitivity for the EM data measured at the at least one physical EM sensor operating from the start of the survey up to the given time moment t using a perturbation of the electrical conductivity within the moving sensitivity domain of the physical EM source and physical EM sensor sensitivities of the at least one moving platform;

e. comparing the computed predicted EM data with the EM data measured at the at least one physical EM sensor to determine an error value between the predicted EM data and the measured EM data;

f. constructing a temporal 3D volume image of the electrical conductivity for the given time moment t when the error value is less than a predetermined threshold value by applying an iterative linearized inversion and/or migration with line search and/or preconditioning to the temporal EM data measured by the at least one moving platform from the start of the survey up to the given time moment t; and

g. outputting the temporal 3D image,

wherein when the error value is greater than the predetermined threshold value;

the initial 3D electrical conductivity model is updated and an updated predicted at least one component of EM data is calculated;

the updated predicted at least one component of EM data is compared with the EM data measured at the at least one physical EM sensor to determine an updated error value between the predicted EM data and the measured EM data; and

the temporal 3D volume image is constructed when the updated error value is less than the predetermined threshold value.

2. The method of claim 1, wherein the electrical conductivity comprises one of conductivity, dielectric permittivity, and/or induced polarization parameters, representing the physical properties of the examined medium containing natural structures or man-made objects.

3. The method of claim 1, wherein the at least one physical EM sensor comprises a plurality of physical EM sensors arranged in an array.

4. The method of claim 3, wherein the plurality of physical EM sensors include inductive and/or galvanic and/or capacitive sensors.

5. The method of claim 1, wherein the physical EM sources may be controlled EM sources including man-made inductive sources and/or man-made galvanic sources located at at least one fixed position with respect to the at least one moving platform.

6. The method of claim 1, wherein the physical EM sources may be controlled EM sources including man-made inductive sources and/or man-made galvanic sources located on the at least one moving platform.

7. The method of claim 1, wherein the physical EM sources may be natural EM sources.

8. The method of claim 1, wherein the 3D modeling, inversion and/or migration of the EM data includes an algorithm based on a numerical solution of Maxwell'"'"'s equations in either the frequency-domain or the time-domain including but not limited to semi-analytical, finite difference, finite element, boundary element, integral equation and/or hybrid numerical methods.

9. The method of claim 1, wherein the 3D modeling comprises of algorithms based on linear approximations.

10. The method of claim 1, wherein imaging is based on the inversion and/or migration comprised of

a) an algorithm based on an iterative linearized method and/or line search and/or preconditioning technique;

b) temporal sensitivities and/or their actions calculated implicitly and/or explicitly using adjoint operators;

c) temporal sensitivities and/or their actions calculated implicitly and/or explicitly using linear approximations;

d) an algorithm based on regularization including smooth and/or focusing stabilizers and/or combinations thereof;

e) an algorithm based on a temporal moving sensitivity domain of the physical EM source and EM sensor sensitivities;

f) an algorithm based using the initial 3D electrical conductivity model at the time moment t_n may be constructed from in real time from the 3D electrical conductivity model at the time moment t_n-1.

11. The method of claim 1, wherein at least one moving platform is a vessel.

12. The method of claim 1, wherein at least one moving platform is a wireline device.

13. The method of claim 1, wherein at least one moving platform is a bottom hole assembly.

14. The method of claim 1, wherein at least one moving platform is an unattended aerial system.

15. The method of claim 1, wherein at least one moving platform is a helicopter.

16. The method of claim 1, wherein at least one moving platform is a fixed wing aircraft.

17. The method of claim 1, wherein at least one moving platform is an airship.

18. The method of claim 1, wherein at least one moving platform is a vehicle.

19. The method of claim 1, wherein the examined medium contains a geological structure.

20. The method of claim 1, wherein volume images for variations in the subsurface electrical conductivity may be obtained from time-lapsed surveys.

21. A physical non-transitory computer readable medium having stored thereon computer executable instructions that when executed by a processor cause a computing system to perform a method for rapid real time imaging of electrical conductivity from moving platforms using at least one physical EM source and/or physical EM sensor placed in at least one position on at least one moving platform, where the moving platform is moved from the start of a survey up to a given time moment t, the method comprising:

a. measuring while the moving platform is moving at least one component of electric and/or magnetic field data with the at least one physical EM sensor in at least one receiving position on the moving platform along at least one survey line by the at least one moving platform from the start of the survey up to the given time moment t;

b. computing predicted at least one component of EM data from the start of the survey up to the given time moment t by use of an initial 3D electrical conductivity model that is based on known information regarding an examined medium;

c. calculating a temporal sensitivity for the EM data measured at the at least one physical EM sensor operating from the start of the survey up to the given time moment t using a perturbation of the electrical conductivity within the moving sensitivity domain of the physical EM source and physical EM sensor sensitivities of the at least one moving platform;

d. comparing the computed predicted EM data with the EM data measured at the at least one physical EM sensor to determine an error value between the predicted EM data and the measured EM data;

e. constructing a temporal 3D volume image of the electrical conductivity for the given time moment t when the error value is less than a predetermined threshold value by applying an iterative linearized inversion and/or migration with line search and/or preconditioning to the temporal EM data measured by the at least one moving platform from the start of the survey up to the given time moment t; and

f. outputting the temporal 3D image,

wherein when the error value is greater than the predetermined threshold value;

the initial 3D electrical conductivity model is updated and an updated predicted at least one component of EM data is calculated;

the updated predicted at least one component of EM data is compared with the EM data measured at the at least one physical EM sensor to determine an updated error value between the predicted EM data and the measured EM data; and

the temporal 3D volume image is constructed when the updated error value is less than the predetermined threshold value.

22. A system for rapid real time imaging of electrical conductivity from moving platforms comprising:

a moving platform;

at least one physical EM source and/or physical EM sensor configured to generate and/or measure one component of electric and/or magnetic field data, wherein the at least one physical EM source and/or physical EM sensor are positioned on the moving platform; and

a computing system comprising;

a processor;

one or more physical non-transitory computer readable medium having computer executable instructions stored thereon that when executed by the processor, cause the computing system to perform the following;

a. measure while the moving platform is moving at least one component of electric and/or magnetic field data with the at least one physical EM sensor in at least one receiving position on the moving platform along at least one survey line by the at least one moving platform from the start of the survey up to the given time moment t;

b. compute predicted at least one component of EM data from the start of the survey up to the given time moment t by use of an initial 3D electrical conductivity model that is based on known information regarding the examined medium;

c. calculate a temporal sensitivity for the EM data measured at the at least one physical EM sensor operating from the start of the survey up to the given time moment t using a perturbation of the electrical conductivity within the moving sensitivity domain of the physical EM source and physical EM sensor sensitivities of the at least one moving platform;

d. compare the computed predicted EM data with the EM data measured at the at least one physical EM sensor to determine an error value between the predicted EM data and the measured EM data;

e. constructing a temporal 3D volume image of the electrical conductivity for the given time moment t when the error value is less than a predetermined threshold value by applying an iterative linearized inversion and/or migration with line search and/or preconditioning to the temporal EM data measured by the at least one moving platform from the start of the survey up to the given time moment t; and

f. outputting the temporal 3D image,

wherein when the error value is greater than the predetermined threshold value;

the initial 3D electrical conductivity model is updated and an updated predicted at least one component of EM data is calculated;

the updated predicted at least one component of EM data is compared with the EM data measured at the at least one physical EM sensor to determine an updated error value between the predicted EM data and the measured EM data; and

the temporal 3D volume image is constructed when the updated error value is less than the predetermined threshold value.