Method and system for modeling fractures in ductile rock

Patent metadata

Field	Value
Publication number	US-9305121-B2
Application number	US-201113698243-A
Country	US
Kind code	B2
Filing date	Apr 11, 2011
Priority date	Jun 28, 2010
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

Method and systems for modeling fractures in quasi-brittle materials are provided. An exemplary method included generating a model that incorporates a unified creep-plasticity (UCP) representation into a constitutive model for a ductile rock. The model may be used in a finite element analysis to model hydraulic fractures in the ductile rock.

First claim

What is claimed is:

1. A method for modeling hydraulic fractures in ductile rocks, comprising:
generating, on a computer, a constitutive model for a quasi-brittle material that incorporates unified creep-plasticity (UCP) based on viscoplasticity theory;
performing, on a computer, a finite element analysis using the constitutive model, wherein performing the finite element analysis comprises predicting a J-integral value and a stress field that incorporates a plasticity effect from finite element analysis using the constitutive model;
determining, on a computer, an effective fracture propagation property for the quasi-brittle material based at least in part, upon a result from the finite element analysis;
predicting, on a computer, hydraulic fractures in the quasi-brittle material, wherein predicting hydraulic fractures in the quasi-brittle material comprises predicting a hydraulic fracture of the ductile rocks using a pore pressure cohesive zone model (CZM); and
harvesting hydrocarbon from the fractured rock.

2. The method of claim 1 , further comprising adjusting a hydraulic fracturing parameter based, at least in part, on the fractures predicted in the ductile rock.

3. The method of claim 1 , wherein a ratio between a length of a fracture process zone and a length of a non-linear fracture zone at a tip of a fracture is between about 1:1 and 1:1.5.

4. The method of claim 1 , wherein the ductile rock forms fractures that have a fracture process zone, wherein the fracture process zone is distributed over a finite size volume, and wherein the fracture process zone exhibits strain-softening.

5. The method of claim 4 , wherein a ratio of a length of the fracture process zone to a length of a non-linear fracture zone located at the tip of a fracture is between about 1:1 and 1:1.5.

6. The method of claim 1 , further comprising determining an effective fracture propagation property of the ductile rock.

7. The method of claim 6 , further comprising determining the effective fracture propagation property of the ductile rock using a numerical method.

8. The method of claim 1 , further comprising predicting a fracture in the ductile rock.

9. The method of claim 8 , further comprising adjusting a parameter in a fracturing process based, at least in part, on the predicted fracture in the ductile rock.

10. The method of claim 9 , wherein the parameter is a mass flow rate of a fluid, a pressure of a fluid, or a combination thereof.

11. The method of claim 1 , further comprising determining a flow of hydrocarbon in a fractured ductile rock.

12. A system for modeling fractures in a reservoir, comprising:
a processor;
a storage medium comprising a data structure comprising a model that incorporates unified creep-plasticity (UCP) based on viscoplasticity theory into a constitutive model for a ductile rock; and
a non-transitory computer readable medium comprising code configured to direct the processor to:
perform a finite element analysis of the ductile rock using the model, wherein performing the finite element analysis comprises predicting a J-integral value and a stress field that incorporates a plasticity effect from finite element analysis using the constitutive model; and
predict hydraulic fractures in the ductile rock, wherein predicting hydraulic fractures in the ductile rock comprises using a pore pressure cohesive zone model (CZM), and wherein the prediction is useful for harvesting hydrocarbon from the reservoir.

13. The system of claim 12 , wherein the processor comprises a multi-processor cluster computer system.

14. The system of claim 12 , wherein the computer readable medium comprises code configured to direct the processor to determine the fracture propagation properties of the ductile rock.

15. The system of claim 12 , wherein the computer readable medium comprises code configured to direct the processor to predict a hydraulic fracture in the ductile rock based, at least in part, upon a result from the finite element analysis.

16. The system of claim 12 , wherein the computer readable medium comprises code configured to direct the processor to determine a flow of hydrocarbon in a fractured ductile rock.

17. A non-transitory, computer-readable medium comprising a data structure representing a cohesive fracture-mechanics model that combines a constitutive model with a unified creep-plasticity (UCP) model based on viscoplasticity theory, further comprising code configured to direct a processor to:
perform a finite element analysis using the constitutive model, wherein performing the finite element analysis comprises predicting a J-integral value and a stress field that incorporates a plasticity effect from finite element analysis using the constitutive model;
determine an effective fracture property for a ductile rock based at least in part, upon a result from the finite element analysis; and
predict fractures in the ductile rock, wherein predicting fractures in the ductile rock comprises using a pore pressure cohesive zone model (CZM), and wherein the prediction is useful for harvesting hydrocarbon from the fractures in the ductile rock.

18. A method for harvesting hydrocarbons from a ductile rock formation, comprising:
generating, on a computer, a model that incorporates unified creep-plasticity (UCP) based on viscoplasticity theory into a constitutive model for a ductile rock;
performing, on a computer, a finite element analysis using the model, wherein performing the finite element analysis comprises predicting a J-integral value and a stress field that incorporates a plasticity effect from finite element analysis using the constitutive model;
predicting, on a computer, fractures in a ductile rock formation based, at least in part, upon a result from the finite element analysis, wherein predicting fractures in the ductile rock formation comprises using a pore pressure cohesive zone model (CZM);
fracturing the ductile rock formation using parameters based, at least in part, on the prediction of the fractures; and
harvesting hydrocarbons from the fractured rock.

Assignees

• Yao Yao
• Gosavi Shekhar V
• Searles Kevin H
• Ellison Timothy K
• Exxonmobil Upstream Res Co

Inventors

• Yao Yao
• Gosavi Shekhar V
• Searles Kevin H
• Ellison Timothy K

Classifications

• E21B43/26 Primary

  by forming crevices or fractures · CPC title

• G06F17/5009 Primary

  Physics · mapped topic

• G06F17/5018

  Physics · mapped topic

• G06F30/23 Primary

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title