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Research Papers

The Enigma of Large-Scale Permeability of Gas Shale: Pre-Existing or Frac-Induced?

[+] Author and Article Information
Viet T. Chau, Saeed Rahimi-Aghdam

Department of Civil and Environmental Engineering,
Northwestern University,
Evanston, IL 60208

Cunbao Li

Department of Civil and Environmental Engineering,
Northwestern University,
Evanston, IL 60208;
Key Laboratory of Energy Engineering Safety
and Disaster Mechanics Ministry of Education,
Sichuan University,
Chengdu 610065, China;
College of Architecture and Environment,
Sichuan University,
Chengdu 610065, China

Zdeněk P. Bažant

McCormick Institute Professor
W.P. Murphy Professor of Civil and Mechanical
Engineering and Materials Science,
Northwestern University,
Evanston, IL 60208
e-mail: z-bazant@northwestern.edu

1V. T. Chau, C. Li, and S. Rahimi-Aghdam contributed equally to this work.

2Corresponding author.

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received March 11, 2017; final manuscript received April 7, 2017; published online April 25, 2017. Editor: Yonggang Huang.

J. Appl. Mech 84(6), 061008 (Apr 25, 2017) (11 pages) Paper No: JAM-17-1140; doi: 10.1115/1.4036455 History: Received March 11, 2017; Revised April 07, 2017

The existing commercial programs for simulation of hydraulic fracturing (aka fracking, or frac) of gas (or oil) shale predict parallel vertical cracks to spread in vertical parallel planes, with no lateral branching. These cracks emanate from the perforation clusters on the horizontal wellbore casing, typically spaced 10 m apart or more. For such a large spacing, the rate of gas production observed at the wellhead can be explained only upon making the hypothesis that the large-scale (or regional) permeability of shale is (even at 3 km depth) about 10,000 times higher than the gas permeability of shale measured in the lab on drilled (nondried) shale cores under confining pressures corresponding to shale at the depth of about 3 km. This hypothesis has recently been rendered doubtful by a new three-phase medium theory that takes into account the body forces due to pressure gradients of pore water diffusing into the pores. This theory predicts the fracking to produce a dense system of branched vertical hydraulic cracks with the spacing of about 0.1 m. This value matches the crack spacing deduced from the gas production rate at wellhead based on the actual lab-measured permeability. It is calculated that, to boost the permeability 10,000 times, the width of the pre-existing open (unfilled) natural cracks or joints (whose ages are distributed from one to several hundred million years) would have to be about 2.8 μm (not counting possible calcite deposits in the cracks). But this width is improbably high because, over the geologic time span, the shale must exhibit significant primary and secondary creep or flow. It is shown that the creep must close all the cracks tightly (except for residual openings of the order of 10 nm) even if the cracks are propped open by surface asperities. The inevitability of secondary creep (or steady-state flow) is explained theoretically by activation of new creep sites at stress concentrations caused by prior creep deformation. The time of transition from primary to secondary creep is taken equal to the Maxwell time estimate from geology. The overall conclusion is that the 10,000-fold increase of large-scale permeability is most likely not pre-existing but frac-induced. Although this conclusion will make little difference for long-term forecasts, it would make a major difference for the understanding and control of the frac process.

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References

Soliman, M. , and Grieser, W. , 2010, “ Analyzing, Optimizing Frac Treatments by Means of a Numerical Simulator,” J. Pet. Technnol., 62(7), pp. 22–24. [CrossRef]
Bažant, Z. P. , Salviato, M. , Chau, V. T. , Viswanathan, H. , and Zubelewicz, A. , 2014, “ Why Fracking Works,” ASME J. Appl. Mech., 81(10), p. 101010. [CrossRef]
Chau, V. T. , Bažant, Z. P. , and Su, Y. , 2016, “ Growth Model for Large Branched Three-Dimensional Hydraulic Crack System in Gas or Oil Shale,” Philos. Trans. R. Soc., A, 374(2078), p. 20150418. [CrossRef]
Bažant, Z. P. , and Chau, V. T. , 2016, “ Recent Advances in Global Fracture Mechanics of Growth of Large Hydraulic Crack Systems in Gas or Oil Shale: A Review,” New Frontiers in Oil and Gas Exploration, C. Jin , and G. Cusatis , eds., Springer International Publishing, Cham, Switzerland, Chap. 13.
Yoffe, E. H. , 1951, “ The Moving Griffith Crack,” London, Edinburgh, Dublin Philos. Mag. J. Sci., 42(330), pp. 739–750. [CrossRef]
Ravi-Chandar, K. , and Knauss, W. , 1984, “ An Experimental Investigation Into Dynamic Fracture—III: On Steady-State Crack Propagation and Crack Branching,” Int. J. Fract., 26(2), pp. 141–154. [CrossRef]
Anderson, T. L. , 2005, Fracture Mechanics: Fundamentals and Applications, CRC Press, Boca Raton, FL.
Schlumberger, 2012, “ FracCADE,” Schlumberger, Houston, TX.
NSI Technologies, 2014, “ StimPlan, Version 7.0,” NSI Technologies Inc., Tulsa, OK.
Sakhaee-Pour, A. , and Bryant, S. , 2012, “ Gas Permeability of Shale,” SPE Reservoir Eval. Eng., 15(4), pp. 401–409. [CrossRef]
Mason, J. E. , 2011, “ Well Production Profiles Assess Fayetteville Shale Gas Potential,” Oil Gas J., 109(11), p. 76.
Bazant, Z. P. , 1982, “ Crack Band Model for Fracture of Geomaterials,” Proceedings of the Fourth International Conference on Numerical Methods in Geomechanics (ICONMIG), Edmonton, Canada, May 31–June 4, pp. 1137–1152.
Zoback, M. D. , 2007, Reservoir Goemechanics, Cambridge University Press, Cambridge, UK.
Kwon, O. , Kronenberg, A. K. , Gangi, A. F. , and Johnson, B. , 2001, “ Permeability of Wilcox Shale and Its Effective Pressure Law,” J. Geophys. Res.: Solid Earth, 106(B9), pp. 19339–19353. [CrossRef]
Dong, J. J. , Hsu, J. Y. , Wu, W. J. , Shimamoto, T. , Hung, J. H. , Yeh, E. C. , and Sone, H. , 2010, “ Stress-Dependence of the Permeability and Porosity of Sandstone and Shale From TCDP Hole-A,” Int. J. Rock Mech. Min. Sci., 47(7), pp. 1141–1157. [CrossRef]
Chalmers, G. R. , Ross, D. J. , and Bustin, R. M. , 2012, “ Geological Controls on Matrix Permeability of Devonian Gas Shales in the Horn River and Liard Basins, Northeastern British Columbia, Canada,” Int. J. Coal Geol., 103, pp. 120–131. [CrossRef]
Cui, X. , Bustin, A. M. M. , and Bustin, R. M. , 2009, “ Measurements of Gas Permeability and Diffusivity of Tight Reservoir Rocks: Different Approaches and Their Applications,” Geofluids, 9(3), pp. 208–223. [CrossRef]
Rydzy, M. B. , Patino, J. , Elmetni, N. , and Appel, M. , 2016, “ Stressed Permeability in Shales: Effects of Matrix Compressibility and Fractures—A Step Towards Measuring Matrix Permeability in Fractured Shale Samples,” International Symposium of the Society of Core Analysts (SCA), Snowmass, CO, pp. 1–12.
Chhatre, S. S. , Braun, E. M. , Sinha, S. , Determan, M. D. , Passey, Q. R. , Zirkle, T. E. , and Kudva, R. A. , 2015, “ Steady-State Stress-Dependent Permeability Measurements of Tight Oil-Bearing Rocks,” Petrophysics, 56(2), pp. 116–124.
Ghanizadeh, A. , Bhowmik, S. , Haeri-Ardakani, O. , Sanei, H. , and Clarkson, C. R. , 2015, “ A Comparison of Shale Permeability Coefficients Derived Using Multiple Non-Steady-State Measurement Techniques: Examples From the Duvernay Formation, Alberta (Canada),” Fuel, 140, pp. 371–387. [CrossRef]
Falk, K. , Coasne, B. , Pellenq, R. , Ulm, F. J. , and Bocquet, L. , 2015, “ Subcontinuum Mass Transport of Condensed Hydrocarbons in Nanoporous Media,” Nat. Commun., 6, p. 6949.
Klinkenberg, L. J. , 1941, “ The Permeability of Porous Media to Liquids and Gases,” American Petroleum Institute, New York, pp. 200–213.
Jones, S. C. , 1994, “ A New, Fast, Accurate Pressure-Decay Probe Permeameter,” SPE Form. Eval., 9(3), pp. 193–199. [CrossRef]
Gensterblum, Y. , Ghanizadeh, A. , Cuss, R. J. , Amann-Hildenbrand, A. , Krooss, B. M. , Clarkson, C. R. , and Zoback, M. D. , 2015, “ Gas Transport and Storage Capacity in Shale Gas Reservoirs: A Review—Part A: Transport Processes,” J. Unconv. Oil Gas Resour., 12, pp. 87–122. [CrossRef]
Monteiro, P. J. M. , Rycroft, C. H. , and Barenblatt, G. I. , 2012, “ A Mathematical Model of Fluid and Gas Flow in Nanoporous Media,” Proc. Natl. Acad. Sci., 109(50), pp. 20309–20313. [CrossRef]
Brace, W. F. , 1980, “ Permeability of Crystalline and Argillaceous Rocks,” Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 17(5), pp. 241–251. [CrossRef]
Brace, W. F. , 1984, “ Permeability of Crystalline Rocks: New in Situ Measurements,” J. Geophys. Res.: Solid Earth, 89(B6), pp. 4327–4330. [CrossRef]
Huenges, E. , Erzinger, J. , Keck, J. , Engeser, B. , and Kessels, W. , 1997, “ The Permeable Crust: Geohydraulic Properties Down to 9101 m Depth,” J. Geophys. Res.: Solid Earth, 102(B8), pp. 18255–18265. [CrossRef]
Townend, J. , and Zoback, M. D. , 2000, “ How Faulting Keeps the Crust Strong,” Geology, 28(5), pp. 399–402. [CrossRef]
Zoback, M. D. , and Townend, J. , 2001, “ Implications of Hydrostatic Pore Pressures and High Crustal Strength for the Deformation of Intraplate Lithosphere,” Tectonophysics, 336(1), pp. 19–30. [CrossRef]
Massarotto, P. , 2002, “ 4-D Coal Permeability Under True Triaxial Stress and Constant Volume Conditions,” Ph.D. thesis, The University of Queensland, Brisbane, Australia.
Sereshki, F. , 2005, “ Improving Coal Mine Safety by Identifying Factors That Influence the Sudden Release of Gases in Outburst Prone Zones,” Ph.D. thesis, University of Wollongong, New South Wales, Australia.
Han, F. , Busch, A. , Krooss, B. M. , Liu, Z. , van Wageningen, N. , and Yang, J. , 2010, “ Experimental Study on Fluid Transport Processes in the Cleat and Matrix Systems of Coal,” Energy Fuel, 24(12), pp. 6653–6661. [CrossRef]
Pan, Z. , Connell, L. D. , and Camilleri, M. , 2010, “ Laboratory Characterisation of Coal Reservoir Permeability for Primary and Enhanced Coalbed Methane Recovery,” Int. J. Coal Geol., 82(3), pp. 252–261. [CrossRef]
Ghanizadeh, A. , Gasparik, M. , Amann-Hildenbrand, A. , Gensterblum, Y. , and Krooss, B. M. , 2014, “ Experimental Study of Fluid Transport Processes in the Matrix System of the European Organic-Rich Shales—I: Scandinavian Alum Shale,” Mar. Pet. Geol., 51, pp. 79–99. [CrossRef]
Hildenbrand, A. , Schlämer, S. , and Krooss, B. M. , 2002, “ Gas Breakthrough Experiments on Fine-Grained Sedimentary Rocks,” Geofluids, 2(1), pp. 3–23. [CrossRef]
Hildenbrand, A. , Schlämer, S. , Krooss, B. M. , and Littke, R. , 2004, “ Gas Breakthrough Experiments on Pelitic Rocks: Comparative Study With N2, CO2 and CH4,” Geofluids, 4(1), pp. 61–80. [CrossRef]
Amann-Hildenbrand, A. , Bertier, P. , Busch, A. , and Krooss, B. M. , 2013, “ Experimental Investigation of the Sealing Capacity of Generic Clay-Rich Caprocks,” Int. J. Greenhouse Gas Control, 19, pp. 620–641. [CrossRef]
Bažant, Z. P. , 1972, “ Thermodynamics of Interacting Continua With Surfaces and Creep Analysis of Concrete Structures,” Nucl. Eng. Des., 20(2), pp. 477–505. [CrossRef]
Wang, C. Y. , and Beckermann, C. , 1993, “ A Two-Phase Mixture Model of Liquid-Gas Flow and Heat Transfer in Capillary Porous Media—I: Formulation,” Int. J. Heat Mass Transfer, 36(11), pp. 2747–2758. [CrossRef]
Schmitt, L. , Forsans, T. , and Santarelli, F. J. , 1994, “ Shale Testing and Capillary Phenomena,” Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 31(5), pp. 411–427. [CrossRef]
Murrell, S. A. F. , 1976, “ Rheology of the Lithosphere—Experimental Indications,” Tectonophysics, 36(1–3), pp. 5–24. [CrossRef]
Birger, B. I. , 2012, “ Transient Creep and Convective Instability of the Lithosphere,” Geophys. J. Int., 191(3), pp. 909–922.
Ranalli, G. , 1987, Rheology of the Earth, Allen & Unwin, Boston, MA, Sec. 8.3.
Sone, H. , and Zoback, M. D. , 2014, “ Time-Dependent Deformation of Shale Gas Reservoir Rocks and Its Long-Term Effect on the In Situ State of Stress,” Int. J. Rock Mech. Min. Sci., 69, pp. 120–132.
Sone, H. , and Zoback, M. D. , 2013, “ Mechanical Properties of Shale-Gas Reservoir Rocks Part—2: Ductile Creep, Brittle Strength, and Their Relation to the Elastic Modulus,” Geophysics, 78(5), pp. D393–D402. [CrossRef]
Rassouli, F. , and Zoback, M. , 2016, “ A Comparison of Short-Term and Long-Term Creep Experiments in Unconventional Reservoir Formations,” 50th U.S. Rock Mechanics/Geomechanics Symposium, American Rock Mechanics Association, Houston, TX, June 26–29, p. ARMA-2016-430.
Carter, N. L. , and Ave’Lallemant, H. G. , 1970, “ High Temperature Flow of Dunite and Peridotite,” Geol. Soc. Am. Bull., 81(8), pp. 2181–2202. [CrossRef]
Raleigh, C. B. , and Kirby, S. H. , 1970, “ Creep in the Upper Mantle,” Mineral. Soc. Am. Spec. Pap., 3, pp. 113–121.
Murrell, S. A. F. , and Chakravarty, S. , 1973, “ Some New Rheological Experiments on Igneous Rocks at Temperatures Up to 1120°C,” Geophys. J. Int., 34(2), pp. 211–250. [CrossRef]
Cotrell, A. H. , 1964, The Mechanical Properties of Matter, Wiley, New York.
Meyers, M. A. , and Chawla, K. K. , 1999, Mechanical Behavior of Materials, Prentice Hall, Upper Saddle River, NJ, pp. 555–557.
Gale, J. F. , Reed, R. M. , and Holder, J. , 2007, “ Natural Fractures in the Barnett Shale and Their Importance for Hydraulic Fracture Treatments,” AAPG Bull., 91(4), pp. 603–622. [CrossRef]
Inglis, C. E. , 1913, “ Stresses in a Plate Due to the Presence of Cracks and Sharp Corners,” Trans. Inst. Nav. Archit., 55, pp. 219–230.
Timoshenko, S. P. , and Goodier, J. N. , 1970, Theory of Elasticity, 3rd ed., McGraw-Hill, New York, p. 193.
Gale, J. F. W. , Laubach, S. E. , Olson, J. E. , Eichhubl, P. , and Fall, A. , 2014, “ Natural Fractures in Shale: A Review and New Observations,” AAPG Bull., 98(11), pp. 2165–2216. [CrossRef]
Dutton, S. P. , White, C. D. , Willis, B. J. , and Novakovic, D. , 2002, “ Calcite Cement Distribution and Its Effect on Fluid Flow in a Deltaic Sandstone, Frontier Formation, Wyoming,” AAPG Bull., 86(12), pp. 2007–2021.
Bažant, Z. P. , and Ohtsubo, H. , 1977, “ Stability Conditions for Propagation of a System of Cracks in a Brittle Solid,” Mech. Res. Commun., 4(5), pp. 353–366. [CrossRef]
Bažant, Z. P. , and Ohtsubo, R. , 1978, “ Geothermal Heat Extraction by Water Circulation Through a Large Crack in Dry Hot Rock Mass,” Int. J. Numer. Anal. Method Geomech., 2(4), pp. 317–327. [CrossRef]
Bažant, Z. P. , Ohtsubo, R. , and Aoh, K. , 1979, “ Stability and Post-Critical Growth of a System of Cooling or Shrinkage Cracks,” Int. J. Fract., 15(5), pp. 443–456. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Parallel hydraulic cracks as predicted in current practice (a single crack per perforation cluster, with no branching), pictured before localization [2]

Grahic Jump Location
Fig. 2

Crack branching in a horizontal frac domain 5 m × 5 m simulated in Ref. [3] by three-phase medium theory with body forces due to pore pressure gradients: (a) for full fracture energy Gf and tensile strength ft of crack band model [12] and (b) for Gf=ft=0 [3] (the horizontal wellbore lies at the bottom of each square shown, and the frac water is injected at constant pressure from three perforations clusters on the wellbore)

Grahic Jump Location
Fig. 3

Permeability of shale: (a) the effect of volumetric (or hydrostatic) confining stress (test data reported in Ref. [16]) and (b) the effect of creep (test data reported in Ref. [19])

Grahic Jump Location
Fig. 4

Idealized array of parallel planar pre-existing natural cracks, assumed to calculate gas transport to adjacent primary hydraulic cracks spaced at L = 10 m

Grahic Jump Location
Fig. 5

(a) Three phases of creep evolution under constant stress, (b) creep evolution over 200 million years when only the primary creep terms are considered, and (c) the same when the secondary creep (or flow) is included

Grahic Jump Location
Fig. 6

Active creep sites (left) and newly created creep sites (right) of bond breakage at stress concentrations in the nanoscale of shale subjected to shear under confining pressure: (a) during the primary (or transient) creep, (b) during the secondary creep (or steady-state flow), and (c) creep sites (stress concentrations)

Grahic Jump Location
Fig. 7

Sequence of creep closure of the cross section of an elliptical channel, calculated for the expected and greatly increased values of Maxwell time τM of shale

Grahic Jump Location
Fig. 8

(a) Idealization of planar crack in shale kept open by asperities imagined as rectangular pillar walls and (b) subsequent states of creep closure for the expected and greatly increased values of Maxwell time τM of shale

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