**7. Conclusions**


**•** Preliminary work on the modeling of shear failure region (SRV) shows that no shear events are detected when a high value of uniaxial compressive strength (UCS) of the rock is assumed, representative of intact rock. A narrow shear region is predicted when the UCS is lowered to represent media with pre-existing fractures or planes of weakness.

This work demonstrates the need for coupled geomechanical modeling in injection to capture poroelastic effects and stress alterations during stimulation.

#### **Nomenclature**

and natural fractures then will predict possibility of shear fracturing and shear-generated SRV creation. However, the SRV based on shear failure is still very narrow and therefore one has to conclude that the majority of the matrix permeability enhancement should be contributed to matrix and micro-fractures. These results are preliminary and further work should be done

using finer gridding and elasto-plastic modeling.

322 Effective and Sustainable Hydraulic Fracturing

**Figure 8.** Stress level after 237 mins of injection – Co= 4657 psi – YZ cross section – Well A

**•** The method used for modeling the fracture propagation is practical, and provides realistic representation of fracturing in reservoir models or coupled geomechanical models.

**•** Uncoupled modeling is not capable of history matching the injection pressures for the two

**•** Coupled modeling achieves reasonable history match of both wells. The main factors that have been identified as important are the fracture permeability factor (*Rfa*) (which primarily shifts the pressure curve), the reservoir permeability dependence on stress and confining the length of fracture propagation (which causes to increase of pressure in later part of the

**•** Value of Biot's constant controls the increase of effective stresses during pumping. For larger

values of Biot's constant it is very difficult to fracture the formation.

**7. Conclusions**

wells studied.

job and thus improves the matches).

*Af* = Fracture cross sectional area, ft2 *Am*= Matrix block cross sectional area, ft2 BHIP = Bottomhole injection pressure, psi *Co* =Uniaxial compressive strength (UCS), psi *E*= Elastic modulus, psi *H <sup>f</sup>* = Fracture half height, ft *K <sup>f</sup>* = Fracture permeability, mD *Km*= Matrix block permeability, mD *L <sup>f</sup>* = Fracture half length, ft MS = Microseismic *P <sup>f</sup>* = Fluid (fluid) pressure, psi *Rfa*= Permeability enhancement/reduction factor *P foc*= Fracture opening or closing pressure, psi *S*= Stress factor SPF = Single planer fracture SRV = Stimulated reservoir volume, ft3 *SL=* Stress level *Tr*= Transmissibility multiplier UTS = Ultimate tensile strength, psi *W* = Grid block size in x-direction, ft *W <sup>f</sup>* = Fracture width, ft

*α*= Biot's constant

*υ*= Poisson's ratio

#### **Acknowledgements**

We would like to acknowledge help from Taurus Reservoir Solutions Ltd. for providing the TRS® reservoir and GeoSim® geomechanical simulator. We also wish to acknowledge the financial aid from the JIP consortium for Tight Gas Sands and Shale Gas Modeling at University of Calgary for supporting the research fund. We wish to thank Vikram Sen for helping during this project and Apache Canada for providing us data for this study.

[5] Ji, L., Settari, A., and Sullivan, R. B. 2009. A Novel Hydraulic Fracturing Model Fully Coupled with Geomechanics and Reservoir Simulation. *SPE Journal* 14 (3): 423-430.

Injection Modeling and Shear Failure Predictions in Tight Gas Sands — A Coupled …

http://dx.doi.org/10.5772/56312

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[6] Weng, X., Kresse, O., Cohen, C. et al. 2011. Modeling of Hydraulic-Fracture-Network Propagation in a Naturally Fractured Formation. *SPE Prod & Oper* 26 (4): 368-380.

[7] Settari, A., Puchyr, P. J., and Bachman, R. C. 1990. Partially Decoupled Modeling of

[8] Settari, A., Sullivan, R. B., Walters, D. A. et al. 2002a. 3-D Analysis and Prediction of Microseismicity in Fracturing by Coupled Geomechanical Modeling. Paper SPE 75714 presented at the SPE Gas Technology Symposium, Calgary, Alberta, 28 April –

[9] Sneddon, I. N., and Lowengrud, M. 1969. Crack Problems in the Classical Theory of Elasticity, 20-30. New York: SIAM Series in Applied Mathematics, John Wiley &

[10] Perkins, T. K., and Kern, L. R. 1961. Widths of Hydraulic Fractures. *J. Pet Tech* 13 (9):

[11] Tran, D., Settari, A., and Nghiem, L. 2012. Predicting Growth and Decay of Hydraul‐ ic Fracture Width in Porous Media Subjected to Isothermal and Nonisothermal Flow. Paper SPE 162651 presented at the SPE Canadian Unconventional Resources Confer‐

[12] Dean, R.H., and Schmidt, J. H. 2009. Hydraulic-Fracture Predictions With a Fully Coupled Geomechanical Reservoir Simulator. *SPE Journal* 14 (4): 707-714.

[13] Settari, A., Sullivan, R. B., Turk, G. et al. 2009. Comprehensive Coupled Modeling Analysis of Stimulations and Post-Frac Productivity – Case Study of the Wyoming Field. Paper SPE 119394 presented at the 2009 SPE Hydraulic Fracturing Technology

[14] Jeffrey, R., and Settari, A. 1998. An Instrumented Hydraulic Fracture Experiment in Coal. Paper SPE 39908 presented at the 1998 Rocky Mountain Regional/Low Permea‐

Hydraulic Fracturing Process. *SPE Prod Eng* 5 (1): 37-44. SPE-16031.

SPE-110845-PA.

SPE-140253-PA.

2 May.

Sons.

937-949. SPE-89-PA.

SPE-116470-PA.

ence, Calgary, Alberta, Oct. 30 – Nov. 1.

Conference, The Woodlands, Texas, 19–21, January.

bility Reservoirs Symposium, Denver, CO, April 5-8.
