Influence of pore pressure on tensile fracture growth in rocks: a new explanation based on numerical testing

Abstract

The diffusion of pore fluid pressures may create both spatial and temporal effective stress gradients that influence or control the development and evolution of fractures within rock masses. To better understand the controls on fracturing behavior, numerical simulations are performed using a progressive fracture modeling approach that shares many of the same natural kinematic features in rocks, such as fracture growth, nucleation, and termination. First, the pinch-off breaking test is numerically performed to investigate the tensile failure of a rock specimen in a uniform pore pressure field. In this numerical simulation, both mechanical and hydrological properties of a suite of rocks are measured under simulated laboratory conditions. The complete tensional failure process of the rock specimen under pore pressure was reproduced. Second, a double-notched specimen is numerically extended to investigate how the water flow direction or pore pressure gradient influences the fracture growth. An exhaustive sensitivity study is conducted that examines the effects of varying both hydrological and mechanical boundary conditions. The simulation results indicate that local fluid pressure gradients strongly influence the state of stress in the solids and, thereby, fracture growth. Fracture and strength behavior is influenced not only by the pore pressure magnitude on a local scale around the fracture tip, but also by the orientation and distribution of pore pressure gradients on a global scale. Increasing the fracture growth rate increases the local model permeability and decreases the sample strength. The results of this study may provide useful information concerning the degree of hydrological and mechanical coupling action under geologic conditions.

Keywords

pore pressure / effective stress / heterogeneous / numerical simulation / fracture growth / rock

References

[1] Abou-Sayed A S, Brechtel C E, Clifton R J (1978). In situ stress determination by hydrofracturing: a fracture mechanics approach. J Geophys Res, 83(B6): 2851–2862

[2] Berchenko I, Detournay E (1997). Deviation of hydraulic fractures through poroelastic stress changes induced by fluid injection and pumping. Int J Rock Mech Min Sci Geomech Abstr, 34(6): 1009–1019

[3] Biot M A (1941). General theory of three-dimensional consolidation. J Appl Phys, 12(2): 155–164

[4] Blair S C, Cook N G W (1998). Analysis of compressive fracture in rock using statistical techniques: Part I. A non-linear rule-based model. Int J Rock Mech Min Sci, 35(7): 837–848

[5] Boone T J, Wawrzynek P A, Ingraffea A R (1986). Simulation of the fracture process in rock with application to hydrofracturing. In J Rock Mech Min Sci, 23(3): 255–265

[6] Boutt D F, Goodwin L, McPherson B J O L (2009). Role of permeability and storage in the initiation and propagation of natural hydraulic fractures. Water Resour Res, 45(5): W00C13

[7] Bridgman P W (1912). Breaking tests under hydrostatic pressure and conditions of rupture. Philos Mag, 24(139): 63–80

[8] Bruno M S, Nakagawa F M (1991). Pore pressure influence on tensile fracture propagation in sedimentary rock. Int J Rock Mech Min Sci, 28(4): 261–273

[9] De Boer R, Lade P V (1997). The concept of effective stress for soil, concrete and rock. Geotechnique, 47(1): 61–78

[10] Detournay E, Cheng A H D, Roegiers J C, McLennan J D (1989). Poroelasticity considerations in situ stress determination by hydraulic fracturing. Int J Rock Mech Min Sci Geomech Abstr, 26(6): 507–513

[11] Griffith A A (1920). The phenomena of rupture and flow in solids. Phil Trans R Soc, A221: 163–198

[12] Gudmundsson A, Kusumoto S, Simmenes T H, Philipp S L, Larsen B, Lotveit I F (2012). Effects of overpressure variations on fracture apertures and fluid transport. Tectonophysics, 581: 220–230

[13] Haeri H, Shahriar K, Marji M F, Moarefvand P (2013). On the HDD analysis of micro cracks initiation, propagation and coalescence in brittle substances. Arabian Journal of Geosciences, doi: 10.1016/j.tecto.2012.05.003

[14] Haeri H, Shahriar K, Marji M F, Moarefvand P (2014a). Experimental and numerical study of crack propagation and coalescence in pre-cracked rock-like disks. Int J Rock Mech Min Sci, 67: 20–28

[15] Haeri H, Shahriar K, Marji M F, Moarefvand P (2014b). On the strength and crack propagation process of the pre-cracked rock-like specimens under uniaxial compression. Strength Mater, 46(1): 140–152

[16] Holl A, Althaus E, Lempp C, Natau O (1997). The petrophysical behaviour of crustal rocks under the influence of fluids. Tectonophysics, 275(1–3): 253–260

[17] Jaeger J C, Cook N G W (1963). Pinching-off and disking of rocks. J Geophys Res, 68: 1759–1765

[18] Jaeger J C, Cook N G (1979). Fundamental of Rock Mechanics, 3rd Edn. London: Chapman & Hall

[19] Jamveit B, Svensen H, Podladchikov J J, Planke S (2004). Hydrothermal vent complexes associated with sill intrusions in sedimentary basins. Geological Society of London, 234: 233–241

[20] Kessels W, Kuck J (1995). Hydraulic communication in crystalline rock between the two boreholes of the continental deep drilling project in germany. Int J Rock Mech Min Sci Geomech Abstr, 32(1): 37–47

[21] Li L C, Li S H, Tang C A (2014). Fracture spacing behavior in layered rocks subjected to different driving forces: a numerical study based on fracture infilling process. Front Earth Sci, 8(4): 472–489

[22] Li L C, Tang C A, Li G, Wang S Y (2012b). Numerical simulation of 3D hydraulic fracturing based on an improved flow-stress-damage model and a parallel FEM technique. Rock Mech Rock Eng, 45: 801–818

[23] Li L C, Tang C A, Wang S Y (2012a). A numerical investigation of fracture infilling and spacing in layered rocks subjected to hydro-mechanical loading. Rock Mech Rock Eng, 45: 753–765

[24] Li L C, Yang T H, Liang Z Z, Tang C A (2011). Numerical investigation of groundwater outbursts near faults in underground coal mines. Int J Coal Geol, 85(3): 276–288

[25] Lin P, Huang B, Li Q B, Wang R K (2014b). Hazards and seismic reinforcement analysis for typical large dams following the Wenchuan earthquake. Eng Geol, doi: 10.1016/j.enggeo.2014.05.011

[26] Lin P, Zhou W Y, Liu H Y (2014a). Experimental study on cracking, reinforcement and overall stability of the Xiaowan super-high arch dam. Rock Mech Rock Eng, doi: 10.1007/s00603-014-0593-x

[27] Liu H Y, Kou S Q, Lindqvist P A, Tang C A (2004). Numerical studies on the failure process and associated microseismicity in rock under triaxial compression. Tectonophysics, 384(1–4): 149–174

[28] Malvar L J, Fourney M E (1990). A three dimensional application of the smeared crack approach. Eng Fract Mech, 35(1–3): 251–260

[29] McClintock F A, Argon A S (1966). Mechanical Behavior of Materials. MA: Addison-Wesley

[30] Oliver N H S (2001). Linking of regional and local hydrothermal systems in the mid-crust by shearing and faulting. Tectonophysics, 335(1–2): 147–161

[31] Pan P Z, Feng X T, Xu D P, Shen L F, Yang J B (2011). Modelling fluid flow through a single fracture with different contacts using cellular automata. Comput Geotech, 38(8): 959–969

[32] Pan P Z, Rutqvist J, Feng X T, Yan F (2014). An approach for modeling rock discontinuous mechanical behavior under multiphase fluid flow conditions. Rock Mech Rock Eng, 47(2): 589–603

[33] Pearce C J, Thavalingam A, Liao Z, Bicanic N (2000). Computational aspects of the discontinuous deformation analysis framework for modeling concrete fracture. Eng Fract Mech, 65(2–3): 283–298

[34] Renard F, Bernard D, Desrues J, Ougier-Simonin A (2009). 3D imaging of fracture propagation using synchrotron X-ray microtomography. Earth Planet Sci Lett, 286(1–2): 285–291

[35] Rozhko A Y, Podladchikov Y Y, Renard F (2007). Failure patterns caused by localized rise in pore-fluid overpressure and effective strength of rocks. Geophys Res Lett, 34(22): L22304

[36] Rummel F (1987). Fracture mechanics approach to hydraulic fracturing stress measurements. In: Atkinson B, ed. Fracture Mechanics of Rock, New York: Academic Press, 317–239

[37] Shimizu H, Murata S, Ishida T (2011). The distinct element analysis for hydraulic fracturing in hard rock considering fluid viscosity and particle size distribution. Int J Rock Mech Min Sci, 48(5): 712–727

[38] Tang C A, Tham L G, Lee P K K, Yang T H, Li L C (2002). Coupled analysis of flow, stress and damage (FSD) in rock failure. Int J Rock Mech Min Sci, 39(4): 477–489

[39] Terzaghi K (1943). Theoretical Soil Mechanics. New York: John Wiley and Sons

[40] Wangen M (2011). Finite element modeling of hydraulic fracturing on a reservoir scale in 2D. J Petrol Sci Eng, 77(3–4): 274–285

[41] Wang R, Kemeny JM (1994). Rock Mechanics. Rotterdam: Balkema

[42] Weibull W (1951). A statistical distribution function of wide applicability. J Appl Mech, 18: 293–297

[43] Wong T F, Wong R H C, Chau K T, Tang C A (2006). Microcrack statistics, Weibull distribution and micromechanical modeling of compressive failure in rock. Mech Mater, 38(7): 664–681

[44] Wu K, Paton D, Zha M (2013). Unconformity structures controlling stratigraphic reservoirs in the north-west margin of Junggar basin, North-west China. Front Earth Sci, 7(1): 55–64

[45] Yang T H, Tham L G, Tang C A, Liang Z Z, Tsui Y (2004). Influence of heterogeneity of mechanical properties on hydraulic fracturing in permeable rocks. Rock Mech Rock Eng, 37(4): 251–275

[46] Yu J, Li H, Chen X, Cai Y, Mu K (2014). Experimental study of permeability and acoustic emission characteristics of sandstone during processes of unloading confining pressure and deformation. Chin J Rock Mech Eng, 33(1): 69–79

[47] Yuan S C, Harrison J P (2005). Development of a hydro-mechanical local degradation approach and its application to modelling fluid flow during progressive fracturing of heterogeneous rocks. Int J Rock Mech Min Sci, 42(7–8): 961–984

[48] Zhu W C, Liu J, Yang T H, Sheng J C, Elsworth D (2006). Effects of local rock heterogeneities on the hydromechanics of fractured rocks using a digital image-based technique. Int J Rock Mech Min Sci, 43(8): 1182–1199

[49] Zhu W C, Tang C A (2004). Micromechanical model for simulating the fracture process of rock. Rock Mech Rock Eng, 37(1): 25–56

Acknowledgements

The study presented in this paper was jointly supported by grants from PetroChina Innovation Foundation (No. 2013D-5006-0211) and the National Natural Science Foundation of China (Grant No. 51479024). The authors are grateful for their support.

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg