Method for providing a calibrated rock-physics model of a subsoil

1. A method for providing a calibrated rock-physics model of a subsoil using a processor for determining the rock physics of each cell of the subsoil for geoscientific characterization of a subsoil, the method comprising:

measuring seismic data with a seismic sensor,

receiving a geological model of the subsoil, the geological model comprising a grid made of cells, each cell being associated with at least one rock-physics parameter,

selecting at least one group of cells forming a calibration body in the grid, the calibration body corresponding to a region of the subsoil having substantially homogenous rock-physics parameter values across said region; the calibration body does not comprise all the cells of the grid,

calibrating at least one adjustable constant parameter in a physical equation expressing a relationship between the at least one rock-physics parameter and at least one petro-elastic parameter in the calibration body, so as to reduce a mismatch between a value of the at least one petro-elastic parameter estimated using the physical equation and a value of the at least one petro-elastic parameter determined from inverted seismic data, the calibrated physical equation providing through the processor a calibrated rock-physics model of the subsoil in the calibration body;

wherein the method further comprises, prior to calibrating the at least one adjustable constant parameter and after selecting at least one group of cells forming a calibration body: comparing values of the at least one rock-physics parameter from cells of the calibration body and determining a standard deviation of said values; and updating the calibration body if the standard deviation exceeds a predetermined threshold.

2. The method according to claim 1 , wherein selecting the at least one group of cells forming the calibration body is performed by:

selecting cells belonging to a same homogenous facies of the subsoil.

3. The method according to claim 1 , wherein selecting the at least one group of cells forming the calibration body is performed by:

selecting cells corresponding to a region of the subsoil that is subject to a single physical phenomenon responsible for a variation of the at least one rock-physics parameter as a function of time.

4. The method according to claim 1 , wherein selecting the at least one group of cells forming the calibration body is performed by:

selecting cells comprising at least one cell adjacent to a well providing production data.

5. The method according to claim 1 , wherein updating the calibration body is performed by:

removing from the calibration body a cell at which a value of the at least one rock-physics parameter differs from a mean value by more than a predetermined amount.

6. The method according to claim 1 , wherein updating the calibration body is performed by:

modifying the value of the at least one rock-physics parameter within a predetermined uncertainty range in accordance with available data.

7. The method according claim 1 , wherein comparing values of the at least one rock-physics parameter from cells of the calibration body and determining a standard deviation of said values is implemented in time at dates of four-dimensional data for base and monitor values of the at least one rock-physics parameter to estimate spatial coherence of said values in the calibration body at different times, wherein the at least one rock-physics parameter is a static rock-physics parameter.

8. The method according to claim 1 , wherein calibrating at least one adjustable constant parameter is implemented on four dimensional data.

9. The method according to claim 1 , wherein calibrating at least one adjustable constant parameter is implemented on three dimensional data.

10. The method according to claim 1 , further comprising:

using the rock-physics model to predict a future evolution of the subsoil.

11. The method according to claim 1 , further comprising:

using the rock-physics model to modify the geological model of the subsoil when the at least one rock-physics parameter obtained via three-dimensional seismic inversion substantially differs from an evolution of the at least one petro-elastic parameter estimated using the rock-physics model.

12. The method according to claim 1 , further comprising:

using the rock-physics model to modify the geological model of the subsoil when an evolution over time of the at least one rock-physics parameter obtained via seismic inversion substantially differs from an evolution of the at least one petro-elastic parameter estimated using the rock-physics model.

13. The method according to claim 1 , wherein the at least one rock-physics parameter is selected from among static parameters and dynamic parameters.

14. The method according to claim 13 , wherein the at least one rock-physics parameter is chosen from among:

a seismic wave propagation speed in cells of the calibration body,

a static rock-physics parameter chosen from among: clay volume in cells of the calibration body,

a porosity of the medium in cells of the calibration body, a water saturation of the medium in cells of the calibration body, a gas saturation of the medium in cells of the calibration body, an initial pressure in the medium in cells of the calibration body, a temperature in cells of the calibration body, a variation in temperature in cells of the calibration body, and

a dynamic rock-physics parameter chosen from among: a change in pressure of the medium in cells of the calibration body, a variation in water saturation of the medium in cells of the calibration body, a variation in gas saturation of the medium in cells of the calibration body, a variation of the porosity of the medium in cells of the calibration body, a temperature in cells of the calibration body, a variation in temperature in cells of the calibration body.

15. A non-transitory computer readable storage medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and adapted to cause the data-processing unit to carry out a method for estimating a calibrated rock-physics model of a subsoil for applications in geoscientific characterization of a subsoil, comprising:

measuring seismic data with a seismic sensor,

obtaining a geological model of the subsoil, the geological model comprising a grid made of cells, each cell being associated with at least one rock-physics parameter,

selecting at least one group of cells forming a calibration body in the grid, the calibration body corresponding to a region of the subsoil having substantially homogenous rock-physics parameter values across said region, the calibration body does not comprise all the cells of the grid; and

calibrating at least one adjustable constant parameter in a physical equation expressing a relationship between the at least one rock-physics parameter and at least one petro-elastic parameter in the calibration body, so as to reduce a mismatch between a value of the at least one petro-elastic parameter estimated using the physical equation and a value of the at least one petro-elastic parameter determined from inverted seismic data, the calibrated physical equation providing a calibrated rock-physics model of the subsoil in the calibration body when the computer program is run by the data-processing device,

wherein the method further comprises, prior to calibrating the at least one adjustable constant parameter and after selecting at least one group of cells forming a calibration body:

comparing values of the at least one rock-physics parameter from cells of the calibration body and determining a standard deviation of said values; and

updating the calibration body if the standard deviation exceeds a predetermined threshold.