Method of constraining seismic inversion

Patent metadata

Field	Value
Publication number	US-10067264-B2
Application number	US-201414895960-A
Country	US
Kind code	B2
Filing date	May 23, 2014
Priority date	Jun 4, 2013
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

Disclosed is a method a seismic inversion for petrophysical properties of a subsurface volume comprising the steps of: obtaining petrophysical data relating to valid geological and/or dynamical scenarios, converting this data into valid combinations of elastic parameters; projecting the valid combinations of elastic parameters onto a spherical plot; and determining a penalty term from the distances between each cell of the spherical plot and the nearest valid combination of elastic parameters within the subsurface volume. Valid geological and/or dynamical scenarios comprise those which are petrophysically possible. The penalty term is then used to constrain an inversion minimizing a cost function associated with seismic mismatch between two or more seismic surveys.

First claim

The invention claimed is:

1. A method of performing a geometric inversion of seismic data comprising the steps of:
obtaining petrophysical data relating to valid geological and/or dynamical scenarios within a subsurface volume comprising a hydrocarbon reservoir or region thereof, wherein valid geological and/or dynamical scenarios comprise those which are petrophysically possible;
converting said petrophysical data into valid combinations of elastic parameters;
projecting said valid combinations of elastic parameters onto a spherical plot;
determining a penalty term from the distances between each cell of the spherical plot and the nearest valid combination of elastic parameters;
performing an inversion which inverts for changes in dynamic properties of the hydrocarbon reservoir by minimizing a cost function associated with seismic mismatch between two or more seismic surveys and at least a synthetic dataset computed from said elastic parameters; wherein said penalty term is used to constrain said inversion; and
using the result of said inversion in predicting performance of said hydrocarbon reservoir.

2. A method as claimed in claim 1 wherein the projection of said valid combinations of elastic parameters onto a spherical plot comprises projection onto the surface of a plotted sphere, and the determined distance between each cell of the spherical plot and the nearest valid combination of elastic parameters is the great circle distance.

3. A method as claimed in claim 1 wherein, when the inversion is a 3D inversion, one of the surveys is the synthetic dataset computed from the inverted parameters.

4. A method as claimed in claim 1 comprising determining the penalty term for only a region of said subsurface volume, wherein said valid geological and/or dynamical scenarios and therefore said valid combinations of elastic parameters are those which are valid for that particular region.

5. A method as claimed in claim 4 comprising determining different penalty terms for different regions within the subsurface volume.

6. A method as claimed in claim 4 wherein each region comprises a different layer of the subsurface volume.

7. A method as claimed in claim 4 comprising the step of using knowledge of the predominant fluid effect in a region in determining valid geological and/or dynamical scenarios for that region.

8. A method as claimed in claim 1 comprising the step of using a simulation to determine said valid geological and/or dynamical scenarios within the subsurface volume.

9. A method as claimed in claim 8 wherein said simulation is a MonteCarlo simulation.

10. A method as claimed in claim 1 comprising the step of using a rock physics/petro-elastic model to convert said petrophysical data into valid combinations of elastic parameters.

11. A method as claimed in claim 1 comprising the step of determining valid combinations of elastic parameters directly from observation.

12. A method as claimed in claim 1 wherein said method comprises 4D modelling of said subsurface volume and the spherical plot is a plot of changes over time in any three elastic parameters, one on each axis.

13. A method as claimed in claim 1 wherein said method comprises 3D modelling of said subsurface volume and the spherical plot is a plot of any three elastic parameters, with one elastic parameter on each axis.

14. A method as claimed in claim 13 comprising determining an origin of the spherical plot of elastic values wherein said determination comprises:
grouping said petrophysical data according to their facies or seismic-facies characteristics;
calculating average values for the elastic parameters being plotted, from the values of each of these parameters for each group of facies characteristic; and
locating said origin at the point defined by said calculated average values for each parameter.

15. A method as claimed in claim 12 wherein said elastic parameters comprise any three of: p-wave velocity or impedance, s-wave velocity or impedance, density and any Lamé parameter.

16. A method as claimed in claim 1 further comprising the step of using the results of said method to aid hydrocarbon recovery from a reservoir.

17. A computer program comprising computer readable instructions which, when run on suitable computer apparatus, cause the computer apparatus to perform the method of claim 1 .

18. A computer program carrier comprising the computer program of claim 17 .

19. Apparatus specifically adapted to carry out the steps of the method as claimed in claim 1 .

20. A method as claimed claim 1 comprising using the result of said inversion in determining future well placement.

Assignees

• Total Sa

Inventors

• Blanchard Thomas David
• Thore Pierre Daniel

Classifications

• G01V1/308

  Time lapse or 4D effects, e.g. production related effects to the formation (fluid flow per se E21B47/00) · CPC title

• G01V2210/6169

  using well-logging · CPC title

• G01V2210/6242

  Elastic parameters, e.g. Young, Lamé or Poisson · CPC title

• G06F17/18

  for evaluating statistical data {, e.g. average values, frequency distributions, probability functions, regression analysis (forecasting specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• G01V1/306 Primary

  for determining physical properties of the subsurface, e.g. impedance, porosity or attenuation profiles · CPC title