1. Overburden Pressure Affects Fracture Aperture and Permeability in a Stress- Sensitive Reservoir Vivek Muralidharan

2. Matrix Porosity Permeability Fracture Permeability

3. Problems Fracture behavior is complex. Overburden Pressure affects fracture parameters.

4. What has been done Observed the change in permeability with overburden pressure (Fatt and Davis, 1952; Jones,1975 and Cook et al, 2001). Measured fracture aperture physically (Jones et al, 1968; Gentier,1986; Arun et al,1997). Studied the effect of overburden pressure using unfractured cores (Holt,1990; Keaney et al,1998).

5. What has not been done Determination of fracture aperture during fluid flow. Determination of matrix and fracture flow contributions.

6. Approach Perform laboratory experiments with different overburden pressure. Develop an equation to determine the fracture aperture and flow contributions. Perform simulation modeling based on experimental results.

7. Approach Perform laboratory experiments with different overburden pressure. Develop an equation to determine the fracture aperture and flow contributions. Perform simulation modeling based on experimental results.

8. Laboratory Experiments How do we analyze the experimental results ? What information can be deduced from experimental results? Fracture Aperture Fracture permeability Matrix and fracture flow contributions How these properties change with overburden stress

9. Experimental Apparatus

10. Permeability changes at variable overburden pressure kmkm k av

11. Approach Perform laboratory experiments with different overburden pressure. Develop an equation to determine the fracture aperture and flow contributions. Perform simulation modeling based on experimental results.

12. Experimental Data Analysis Parallel plate assumption: Fracture Permeability : Combining above equations to determine w: Contribution of flow from matrix and fracture systems: w A l L

13. Fracture Aperture 0 0.001 0.002 0.003 0.004 0.005 0.006 02004006008001000120014001600 Overburden Pressure (Psia) Fracture Aperture (cm) 5 cc/min10 cc/min15 cc/min20 cc/min 500psia1000psia1500psia w w w 5 cc/min 20 cc/min 5 cc/min10 cc/min15 cc/min20 cc/min w w w 5 cc/min 20 cc/min 0 0.001 0.002 0.003 0.004 0.005 0.006 02004006008001000120014001600 ) 5 cc/min10 cc/min15 cc/min20 cc/min w w w 5 cc/min 20 cc/min ) 5 cc/min10 cc/min15 cc/min20 cc/min w w w 5 cc/min 20 cc/min 5 cc/min10 cc/min15 cc/min20 cc/min w w w 5 cc/min 20 cc/min

14. Fracture Permeability OR

15. Fracture Permeability OR W1 W2 W2 < W1

16. Fracture Flow Rate

18. 0.00 5.00 10.00 15.00 20.00 25.00 02004006008001000120014001600 Overburden Pressure (Psia) Matrix Flow Rate (cc/min) 5 cc/min10 cc/min15 cc/min20 cc/min 5 cc/min 20 cc/min 5 cc/min10 cc/min15 cc/min20 cc/min 0 ) 5 cc/min10 cc/min15 cc/min20 cc/min5 cc/min10 cc/min15 cc/min20 cc/min 5 cc/min10 cc/min15 cc/min20 cc/min Matrix Flow Rate

19. Approach Perform laboratory experiments with different overburden pressure. Develop an equation to determine the fracture aperture and flow contributions. Perform simulation modeling based on experimental results.

20. Modeling Laboratory Experiment Is single fracture aperture sufficient for modeling the flow through the fracture? Model for future reservoirs

21. Simulation Parameters  Single phase black oil simulation  Laboratory dimensions (4.9875” x 2.51”)  31x1x31 layers  Matrix porosity = 16.764%  Matrix permeability = 296 md  Fracture properties is introduced in 16 th layer  Fracture porosity = 0.56%  Mean fracture aperture = 56.4 micro meter

22. Example of flow through single fracture aperture

23. Injection Rate Fracture Flow Matrix Flow Outlet Pressure Inlet Pressure Simulation Result for 500 psi and 5cc/min Flow

24. Match between Laboratory data and Simulation Results for 500 psi and 5cc/min flow Observed Simulated Fracture Matrix

25. Match between Laboratory data and Simulation Results for 5 cc/min Observed Simulated

26. Actual Fracture Face

27. Single fracture aperture cannot be used in modeling the experimental data. The fracture aperture must be distributed. Lesson Learned !

28. Log-normal Distribution of Fracture Aperture

29. Variogram Modeling to Generate Fracture Aperture Distribution

30. Core Surface Generated after Krigging

31. Example of flow through different fracture spatial heterogenity

32. 1.Effect of stresses are most pronounced in fractured reservoirs. 2.The fracture aperture equation has been developed and thus, the matrix and fracture flow contributions can be estimated. 3.The spatial heterogeneity in the fracture aperture must be included in the modeling of fracture system. Conclusions

33. Acknowledgement Dr. D. S. Schechter, Texas A&M University Dr. Erwin Putra, Texas A&M University Department of Energy (D.O.E) for sponsoring the project.