Systems and methods for building axes, co-axes and paleo-geographic coordinates related to a stratified geological volume
View Patent ↗A method and system for modeling a subsurface structure at a time when the structure was originally formed. A first model having non-planar horizons representing a current subsurface structure may be used to calculate a vector field based on the non-planar geometry of the horizons of the model. The vector field may be non-uniform or uniform. Geographic coordinates of the first model may be transformed to paleo-geographic coordinates of a model representing the subsurface structure in the past, where the non-planar horizons in the first model are transformed to planar horizons in the second model. A set of points describing one or more fractures in the subsurface structure may be used to calculate a tuning parameter to correct a first set of paleo-geographic coordinates. A second set of coordinates representing an improved prediction at a time period when the subsurface structure was originally formed may be generated.
1. A method for generating a depositional model representing a predicted past geometry of a subsurface structure using a global axis, local axis, and local co-axis, of the subsurface structure in a region of a present day geological domain, the method comprising:
generating a global axis of the subsurface structure in the region of the present day geological domain;
at each point of the subsurface structure in the region of the present day geological domain, computing a vector field of local axis and local co-axis vectors characterizing the approximate local directions of curvature of the subsurface structure using the global axis and a field of normal vectors orthogonal to horizons of the subsurface structure in the region of the present day geological domain;
at each point of the subsurface structure in the region of the present day geological domain, generating paleo-geographic coordinates of the depositional model based on the geometry of the present day configuration of the subsurface structure using the local axis and co-axis vectors, wherein the paleo-geographic coordinates map each point in the region of the present day geological domain to a point in the depositional model representing a predicted past location of one or more particles of sediment when the particles were originally deposited; and
displaying the depositional model using the paled-geographic coordinates visualizing the predicted past geometry of the subsurface structure.
2. The method of claim 1 comprising computing the global axis of the subsurface structure to be an eigen vector associated with the smallest eigen value of a matrix generated using the field of normal vectors orthogonal to the horizons.
3. The method of claim 1 comprising receiving user input selecting the global axis.
4. The method of claim 1 , wherein the patio-geographic coordinates are generated assuming that the subsurface structure had minimal deformation from the past depositional model to the present day geological domain.
5. The method of claim 1 , wherein the patio-geographic coordinates are generated by modeling the deformation of the subsurface structure from the past depositional model to the present day geological domain using infinitely thin modeled layers that slide against each other.
6. The method of claim 1 comprising generating the horizons of the subsurface structure in the present day geological domain using one or more of seismic records and well data collected by probing the subsurface structure.
7. The method of claim 1 comprising representing the depositional model by a geological time t and paleo-geographic coordinates u and v.
8. The method of claim 1 comprising representing the present day geological domain by Cartesian (x,y,z) coordinates.
9. The method of claim 1 , wherein the paleo-geographic coordinates are generated using a set of equations that are linear and independent from each other.
10. The method of claim 1 comprising:
receiving an identification of a gap or an overlap in a planar horizon in the depositional model;
receiving identified points on the planar horizon, wherein the identified points are erroneously generated based on corresponding points of the present day geological domain; and
re-generating the paleo-geographic coordinates of the depositional model so that points of the present day geological domain corresponding to the identified points, generate points on a planar horizon in the depositional model having no gaps and no overlaps.
11. The method of claim 1 comprising receiving geological data representing the present day configuration of the subsurface structure in the region of a present day geological domain, wherein the geological data is seismic data produced in a three-dimensional field by a transmitter emitting seismic waves that reflect at geological discontinuities throughout the subsurface structure and a receiver receiving the reflected seismic waves that correspond to the seismic waves output by the transmitter.
12. A system configured to generate a depositional model representing a predicted past geometry of a subsurface structure using a global axis, local axis, and local co-axis, of the subsurface structure in a region of a present day geological domain, the system comprising:
a memory to store data representing the subsurface structure in the region of the present day geological domain;
a processor configured to:
generate a global axis of the subsurface structure in the region of the present day geological domain,
at each point of the subsurface structure in the region of the present day geological domain, compute a vector field of local axis and local co-axis vectors characterizing the approximate local directions of curvature of the subsurface structure using the global axis and a field of normal vectors orthogonal to horizons of the subsurface structure in the region of the present day geological domain, and
at each point of the subsurface structure in the region of the present day geological domain, generate paled-geographic coordinates of the depositional model based on the geometry of the present day configuration of the subsurface structure using the local axis and co-axis vectors, wherein the paleo-geographic coordinates map each point in the region of the present day geological domain to a point in the depositional model representing a predicted past location of one or more particles of sediment when the particles were originally deposited; and
a display to display the depositional model using the paled-geographic coordinates to visualize the predicted past geometry of the subsurface structure.
13. The system of claim 12 , wherein the processor is configured to compute the global axis of the subsurface structure to be an eigen vector associated with the smallest eigen value of a matrix generated using the field of normal vectors orthogonal to the horizons.
14. The system of claim 12 , wherein the processor is configured to receive user input selecting the global axis.
15. The system of claim 12 , wherein the processor is configured to generate the paled-geographic coordinates assuming that the subsurface structure had minimal deformation from the past depositional model to the present day geological domain.
16. The system of claim 12 , wherein the processor is configured to generate the paler-geographic coordinates by modeling the deformation of the subsurface structure from the past depositional model to the present day geological domain using infinitely thin modeled layers that slide against each other.
17. The system of claim 12 , wherein the processor is configured to generate the horizons of the subsurface structure in the present day geological domain using one or more of seismic records and well data collected by probing the subsurface structure.
18. The system of claim 12 , wherein the processor is configured to represent the depositional model by a geological time t and paled-geographic coordinates u and v.
19. The system of claim 12 , wherein the processor is configured to represent the present day geological domain by Cartesian (x,y,z) coordinates.
20. The system of claim 12 , wherein the processor is configured to generate the paleo-geographic coordinates using a set of equations that are linear and independent from each other.
21. The system of claim 12 , wherein the processor is configured to:
receive an identification of a gap or an overlap in a planar horizon in the depositional model,
receive identified points on the planar horizon, wherein the identified points are erroneously generated based on corresponding points of the present day geological domain, and
re-generate the paleo-geographic coordinates of the depositional model so that points of the present day geological domain corresponding to the identified points, generate points on a planar horizon in the depositional model having no gaps and no overlaps.