Method For Simulating And Estimating Sandstone Properties

• US 20070203677A1
• Filed: 01/26/2005
• Published: 08/30/2007
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Original Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Inventors: Awwiller, David
• Granted Patent: US 7,933,757 B2
• Time in Patent Office: Days
• US Class Current: 703/1
• CPC Class Codes: G01V 11/00 Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00
• CPC Class Codes: G01V 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: G06F 2111/10 Numerical modelling
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

The invention is a method for simulating sandstone deposition. The sandstone is simulated by estimating the grain size distribution and mineral composition of grains in the sandstone, simulating sedimentation of grains from the grain size distribution and mineral composition of the grains, simulating compaction of the grains, and simulating cementation of the grains. Properties of the sandstone such as porosity and permeability may be estimated from the simulated sandstone. The method permits multiple mineralogies to be simulated during the burial history of sedimentation, compaction and cementation.

Claims

1. A method for simulating sandstone deposition comprising:

(a) Estimating grain size distribution and mineral composition distribution of grains in the sandstone;

(b) Simulating of sedimentation of grains using the grain size distribution and the mineral composition distribution of the grains;

(c) Simulating compaction of the sedimented grains;

(d) Simulating cementation of the compacted grains.

2. The method of claim 1 further comprising estimating properties of a sandstone from the simulated sedimentation, compaction and cementation of the grains.

3. The method of claim 2 wherein the properties of the sandstone are selected from the group consisting of permeability, connectivity, porosity and any combination thereof.

4. The method of claim 1 wherein the grain size distribution and mineral composition of grains in the sandstone are measured mineral distributions.

5. The method of claim 1 wherein the grain size distribution and mineral composition of grains in the sandstone are modeled mineral distributions.

6. The method of claim 1 wherein the mineral composition of step (a) is chosen from the group consisting of composition, shape, ductility, and microporosity of that grain, and any combination thereof.

7. The method of claim 1 wherein at least two distinct mineral composition of grains are estimated in step (a) and used to simulate the sedimentation of grains in step (b).

8. The method of claim 1 wherein the type of deformation simulated during the compaction simulation of grains of step (c) is chosen from the group consisting of ductile deformation, elastic deformation, and any combination thereof.

9. The method of claim 1 wherein the simulating of sedimentation of grains of step (b) is done in three-dimensional space.

10. The method of claim 1 wherein the simulating of the sedimentation of grain of step (b) is simulated with at least two mineralogies by assigning each grain a specific weight based on its mineralogy.

11. The method of claim 1 wherein the simulating of compaction of grain of step (c) are modeled by re-arranging and deforming the grains as a result of increasing overburden stress.

12. The method of claim 8 wherein the elastic deformation is modeled by using a following equation:

$\mathrm{dV}=\frac{\mathrm{Vr}}{\mathrm{Vo}}=\mathrm{\kappa <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\sigma <br><br>}$

wherein;

Vr=volume of the grain in presence of a uniform stress field,

Vo=volume of the grain in under atmospheric (no effective stress) conditions,

σ

=effective stress (MPa),

κ

=a compressibility constant (MPa<sup>−

1</sup>)

13. The method of claim 8 wherein ductile deformation is modeled using a following equation:

V_dg=V_ag= 4/3π

r_ug³

wherein;

V_dg=volume of the grain after deformation,

V_ug=volume of the grain before deformation (such as, at time of sedimentation),

r_ug is undeformed grain radius.

14. The method of claim 1 wherein clay is introduced inside pores between the grains.

15. The method of claim 1 wherein during the simulating of cementation of step (d) cement growth rate is calculated using the following expanded Arrhenius kinetic formulation:

rate=(A_Canff_Can+A_Ceuff_Ceu+A_Aanff_Aan+A_Aeuff_Aeu)e<sup>−

Ea/RT</sup>

wherein;

rate=instantaneous nucleation rate (mol·

s<sup>−

1</sup>),

Ceu=euhedrally terminated c-axis growth face,

Can=non-euhedral (‘

anhedral’

) c-axis growth face,

Aeu=euhedrally terminated a-axis growth face,

Aan=non-euhedral (‘

anhedral’

) a-axis growth face,

A_x=surface area corresponding to each of the above-defined growth faces (cm²),

ff_x=Arrhenius preexponential constant corresponding to each of the above-defined growth faces (mol·

cm<sup>−

2</sup>·

s<sup>−

1</sup>),

Ea=activation energy of the nucleation reaction (J·

mol<sup>−

1</sup>),

R=Ideal gas constant (J·

mol<sup>−

1</sup>·

K<sup>−

1</sup>),

T=temperature (K).

16. The method of claim 2 wherein porosity is the property predicted and porosity is directly calculated from the volume after the simulation of sedimentaiton, compaction and cementation has been performed.

17. The method of claim 2 wherein permeability is the property of sandstone predicted and permeability of the sandstone is calculated by a method chosen from the group consisting of bulk-volume method, a Lattice-Bolzmann method, and any combination thereof.

18. The method of claim 1 further comprising using a burial history model to help simulate compaction.

19. The method of claim 1 further comprising using a burial history model to help simulate cementation.

20. The method of claim 1 further comprising adjusting at least one model parameter of at least one simulation step to conform the simulation results to calibration data.