Systems and methods for building axes, co-axes and paleo-geographic coordinates related to a stratified geological volume
View Patent ↗A method, apparatus and system for, in a computing system, modeling a subsurface structure at a time period when the structure was originally formed. A memory may store a first model having a plurality of non-planar horizons representing a current state of the subsurface structure. A processor may compute a vector field based on the non-planar geometry of the horizons of the first model. The vector field may be a non-uniform vector field (e.g., the axe and/or co-axe vector field) or a uniform vector field (e.g., a global axis). Using the vector field, the processor may transform geographic coordinates of the first model to paleo-geographic coordinates of a second model representing a predicted state of the subsurface structure at a time period when the subsurface structure was originally formed, where the non-planar horizons in the first model are transformed to planar horizons in the second model. A display may display the first model.
1. A method for modeling a subsurface structure at a time period when the structure was originally formed, the method comprising:
generating a first model having a plurality of non-planar horizons representing a current state of the subsurface structure;
computing a non-uniform vector field based on the non-planar geometry of the horizons of the first model;
using the vector field, transforming geographic coordinates of the first model to paleo-geographic coordinates of a second model representing a predicted state of the subsurface structure at a time period when the subsurface structure was originally formed, wherein the non-planar horizons in the first model are transformed to planar horizons in the second model; and
displaying the first model.
2. The method of claim 1 , comprising determining a global structural axis based on the geometry of the first model and computing a second vector field, wherein the first vector field and the second vector field are computed based on the geometry of both the horizons in the first model and the global structural axis.
3. The method of claim 2 , comprising automatically computing the global structural axis associated with the first model using the geometry of horizons of the first model.
4. The method of claim 2 , comprising accepting from a user a selection of the global structural axis.
5. The method of claim 2 , wherein the first vector field and the second vector field include vectors generated based on the local geometry of the horizons of the first model and wherein the paleo-geographic coordinates of the second model are generated as functions of the first vector field and the second vector field.
6. The method of claim 1 , wherein each of the paleo-geographic coordinates of the second model is a least squares solution of a plurality of linear and independent equations based on the vector field.
7. The method of claim 1 , wherein the paleo-geographic coordinates of the second model flatten non-planar horizons in the first model.
8. The method of claim 1 , wherein the first model is generated using one or more of seismic records and well data collected by probing the subsurface structure.
9. The method of claim 1 , further comprising:
receiving an identification of a gap or an overlap in one of the planar horizons in the second model;
receiving identified points on the one of the planar horizon, wherein the identified points are erroneously transformed from the corresponding points of the first model; and
re-computing the vector field between the first and second models so that points of the first model which were erroneously transformed to the identified points, are transformed to a planar horizon of the second model having no gaps and no overlaps.
10. The method of claim 9 comprising receiving a segment drawn by a user and identifying the gap or overlap intersected thereby.
11. The method of claim 1 , further comprising generating a global axis A of the subsurface structure represented in the first model, wherein the vector field includes local axis a(x,y,z) and local co-axis b(x,y,z) vectors that are computed at each point (x,y,z) of the subsurface structure using the global axis A and a field of normal vectors orthogonal to horizons of the subsurface structure in the first model and, wherein each point (x,y,z) in the subsurface structure of the first model is transformed to the paleo-geographic coordinates (u(x,y,z), v(x,y,z), t(x,y,z)) of the second model using the local axis a(x,y,z) and co-axis b(x,y,z) vectors.
12. The method of claim 11 , wherein the global axis A of the subsurface structure is computed to be an eigen vector associated with the smallest eigen value of a matrix [m] generated using the field of normal vectors orthogonal to the non-planar horizons in the first model.
13. The method of claim 11 , comprising receiving user input selecting the global axis A.
14. The method of claim 11 , wherein the paleo-geographic coordinates u(x,y,z) and v(x,y,z) are generated assuming that deformation of the subsurface structure from its representation in the first model to its representation in the second model is minimal.
15. The method of claim 11 , wherein the paleo-geographic coordinates u(x,y,z) and v(x,y,z) are generated by modeling the deformation of the subsurface structure from its representation in the first model to its representation in the second model using infinitely thin modeled layers that slide against each other.
16. A system configured to model a subsurface structure at a time period when the structure was originally formed, the system comprising:
a memory to store a first model having a plurality of non-planar horizons representing a current state of the subsurface structure;
a processor configured to compute a non-uniform vector field based on the non-planar geometry of the horizons of the first model, and, using the vector field, to transform geographic coordinates of the first model to paleo-geographic coordinates of a second model representing a predicted state of the subsurface structure at a time period when the subsurface structure was originally formed, wherein the non-planar horizons in the first model are transformed to planar horizons in the second model; and
a display to display the first model.
17. The system of claim 16 , wherein the processor is configured to determine a global structural axis based on the geometry of the first model and to compute a second vector field, wherein the first vector field and the second vector field are computed based on the geometry of both the horizons in the first model and the global structural axis.
18. The system of claim 16 , wherein the processor is configured to automatically compute the global structural axis associated with the first model using the global geometry of horizons of the first model.
19. The system of claim 16 , wherein the processor is configured to accept from a user a selection of the global structural axis.
20. The system of claim 16 , wherein the processor is configured to generate the first vector field and the second vector field to include vectors based on the local geometry of the horizons of the first model and to generate each of the paleo-geographic coordinates of the second model as a function of the first vector field and the second vector field.
21. The system of claim 16 , wherein the processor is configured to generate each of the paleo-geographic coordinates of the second model to be a least squares solution of a plurality of linear and independent equations based on the vector field.
22. The system of claim 16 , wherein the processor is configured to generate the paleo-geographic coordinates of the second model to flatten non-planar horizons in the first model.
23. The system of claim 16 , wherein the processor is configured to generate the first model using one or more of seismic records and well data collected by probing the subsurface structure.