Formation fracturing potential using surrounding pore pressures

Patent metadata

Field	Value
Publication number	US-10190406-B2
Application number	US-201414581255-A
Country	US
Kind code	B2
Filing date	Dec 23, 2014
Priority date	Dec 23, 2014
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

A method for conducting an earth reservoir process includes receiving a stress field of a reservoir that includes a pore pressure field for a rock volume, selecting a search radius extending from a grid cell of interest, and substituting a pore pressure from a plurality of surrounding grid cells within the selected radius for the pore pressure of the grid cell of interest and determining if a critical stress state exists for each of the substituted pore pressures. The method further includes determining a shortest distance to a grid cell in the plurality of surrounding grid cells having a pore pressure that yields a critical stress state when substituted in the grid cell of interest and conducting the earth reservoir process with earth reservoir process apparatus using a parameter related to the determined shortest distance.

First claim

What is claimed is:

1. A method for conducting a selected earth reservoir physical process, the method comprising:
receiving a stress field of a reservoir that includes a pore pressure field for a rock volume;
selecting a search radius extending from a grid cell of interest;
substituting a pore pressure from a plurality of surrounding grid cells within the selected radius for the pore pressure of the grid cell of interest and determining if a critical stress state exists for each of the substituted pore pressures;
determining a shortest distance to a grid cell in the plurality of surrounding grid cells having a pore pressure that yields a critical stress state when substituted in the grid cell of interest; and
at least one of changing an injection pressure of an injected fluid and changing a temperature of an injected fluid in an enhanced production process with enhanced production process apparatus based on the determined shortest distance such that a risk of fracturing rock is reduced;
wherein the receiving, selecting, substituting and determining are performed using a processor.

2. The method according to claim 1 , wherein the search radius comprises the entire earth reservoir.

3. The method according to claim 2 , wherein the search radius is a closest distance to a boundary of the earth reservoir.

4. The method according to claim 1 , wherein the enhanced production process is an enhanced hydrocarbon production process configured to recover hydrocarbons.

5. The method according to claim 4 , wherein the enhanced hydrocarbon production process comprises an enhanced oil recovery process.

6. The method according to claim 5 , wherein the enhanced oil recovery process is a steam assisted gravity drainage process.

7. The method according to claim 6 , further comprising at least one of setting a limit to an operational parameter and changing an operational constraint in the enhanced production process with the enhanced production process apparatus, wherein the at least one of the operational parameter and the operational constraint is an amount of energy to be injected into the earth reservoir.

8. The method according to claim 7 , wherein an amount of steam and/or a steam temperature is controlled to control the amount of energy to be injected.

9. The method according to claim 1 , wherein:
the stress field comprises a stress tensor and calculating comprises determining Eigenvalues of the stress tensor;
determining if a critical stress state exists for each of the substituted pore pressures comprises sorting the Eigenvalues so that SP 1 ≥SP 2 ≥SP 3 and extracting the minimum principal absolute pressures SP 1 and SP 3 for each grid cell in the stress field; and
the method further comprises:
defining a lateral search distance DL;
defining a vertical search distance DV;
determining the local SP 3 value SP 3 ( i ) and its location L(i) for grid cell (i);
determining the pore pressure values PP(j) (j=0 . . . n) which are in the proximity of the grid cell i such that the lateral dL(i,j) distance is smaller or equal to DL and the vertical distance dv(i,j) is smaller or equal to DV only for depths of PP(j) equal or greater as that of cell i; and
determining which PP*(j) are leading to critical Tau Ratios where τratio≥1.0 using the local SP 1 ( i ) and SP 3 ( i ) and the PP*(j=0 . . . n) and storing the smallest distance to a critical value in the grid cell i.

10. The method according to claim 9 , further comprising:
defining a fluid density ρ correction for the pressure correction; and
correcting the fluid density of PP(j) to obtain PP*(j) to accommodate the pressure change due to gravitational effects, such that with a vertical distance of dv(i,j) the pressure PP*(j) is PP*(j)=PP(j)−G·ρ correction ·dv(i,j) with G being a gravitational constant.

11. The method according to claim 9 , further comprising storing a null value for a grid cell (i) if there is no distance to a surrounding grid cell having a pore pressure that when substituted into the grid cell of interest yields a critical stress state for the grid cell of interest.

12. The method according to claim 9 , wherein the critical stress state comprises a shear fracture and the method further comprises providing a value for a sliding friction coefficient η.

13. The method according to claim 1 , further comprising determining a value of probability, likelihood or risk of the grid cell of interest being in fluid communication with the grid cell in the plurality having the determined shortest distance and using the value for conducting the selected earth reservoir physical process.

14. The method according to claim 13 , wherein the probability, likelihood or risk is with respect to other grid cells in the plurality having a pore pressure that when substituted in the grid cell of interest yields a critical stress state.

15. A method for estimating a probability of a slip of a fracture in an earth reservoir, the method comprising:
receiving a stress field of a reservoir that includes a pore pressure field for a rock volume;
selecting a search radius extending from a grid cell of interest;
substituting a pore pressure from a plurality of surrounding grid cells within the selected radius for the pore pressure of the grid cell of interest and determining if a critical stress state exists for each of the substituted pore pressures;
determining a shortest distance to a grid cell in the plurality of surrounding grid cells having a pore pressure that yields a critical stress state when substituted in the grid cell of interest;
transmitting a signal comprising the shortest distance via an output interface to a signal receiving device;
estimating the probability of a slip of a fracture based on the shortest distance; and
at least one of changing an injection pressure of an injected fluid and changing a temperature of an injected fluid in a fluid injection process with fluid injection apparatus based on the estimated probability such that a risk of fracturing rock is reduced;
wherein the receiving, calculating, determining, estimating and using are performed by a processor.

16. The method according to claim 15 , further comprising accounting for gravitational effects in substituting the pore pressure from a plurality of surrounding grid cells.

17. The method according to claim 15 , wherein the signal receiving device comprises at least one of a computer display, printer, memory, storage medium and controller.

18. The method according to claim 15 , wherein the grid cell of interest comprises a plurality of grid cells of interest.

19. The method according to claim 18 , further comprising displaying the shortest distance for each grid cell in the plurality to a user.

20. A non-transitory computer readable medium comprising computer executable instructions for estimating a probability of a slip of a fracture in an earth reservoir that when executed by a computer cause an apparatus to implement a method comprising:
receiving a stress field of a reservoir that includes a pore pressure field for a rock volume;
selecting a search radius extending from a grid cell of interest;
substituting a pore pressure from a plurality of surrounding grid cells within the selected radius for the pore pressure of the grid cell of interest and determining if a critical stress state exists for each of the substituted pore pressures;
determining a shortest distance to a grid cell in the plurality of surrounding grid cells having a pore pressure that yields a critical stress state whe

Assignees

• Holland Marc
• Van Der Zee Wouter
• Baker Hughes A Ge Co Llc

Inventors

• Holland Marc
• Van Der Zee Wouter

Classifications

• E21B49/006

  Measuring wall stresses in the borehole · CPC title

• E21B43/2406

  Steam assisted gravity drainage [SAGD] · CPC title

• G01V2210/6248

  Pore pressure · CPC title

• E21B47/06 Primary

  Measuring temperature or pressure · CPC title