Numerical investigation on permeability evolution behavior of rock by an improved flow-coupling algorithm in particle flow code

Abstract

Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass is very important to elucidate the permeability evolution mechanisms, which is difficult to realize in laboratory, but easy to be achieved in numerical simulations. Therefore, the particle flow code (PFC), a discrete element method, is used to simulate permeability behaviors of rock materials in this study. Owe to the limitation of the existed solid-fluid coupling algorithm in PFC, an improved flow-coupling algorithm is presented to better reflect the preferential flow in rock fractures. The comparative analysis is conducted between original and improved algorithm when simulating rock permeability evolution during triaxial compression, showing that the improved algorithm can better describe the experimental phenomenon. Furthermore, the evolution of pore pressure and flow rate distribution during the flow process are analyzed by using the improved algorithm. It is concluded that during the steady flow process in the fractured specimen, the pore pressure and flow rate both prefer transmitting through the fractures rather than rock matrix. Based on the results, fractures are divided into the following three types: I) fractures link to both the inlet and outlet, II) fractures only link to the inlet, and III) fractures only link to the outlet. The type I fracture is always the preferential propagating path for both the pore pressure and flow rate. For type II fractures, the pore pressure increases and then becomes steady. However, the flow rate increases first and begins to decrease after the flow reaches the stop end of the fracture and finally vanishes. There is no obvious pore pressure or flow rate concentration within type III fractures.

Keywords

rock mechanics / fluid-solid coupling / particle flow code (PFC) / permeability / triaxial compression

References

[1] HoekE, BrownE T. Empirical strength criterion for rock masses [J]. Journal of the Geotechnical Engineering Division, 1980, 106(9): 1013-1035

[2] TownendJ, ZobackM D. How faulting keeps the crust strong [J]. Geology, 2000, 28(5): 399-402

[3] KnipeR J. Faulting processes and fault seal [J]. Structural & Tectonic Modelling & Its Application to Petroleum Geology, 1992325342

[4] ShiptonZ K, EvansJ P, RobesonK R, ForsterC B, SnelgroveS H. Structural heterogeneity and permeability in faulted eolian sandstone: Implications for subsurface modeling of faults [J]. AAPG Bulletin, 2002, 86(5): 863-883

[5] BraceW F. Permeability of crystalline and argillaceous rocks [J]. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1980, 17(5): 241-251

[6] AntonelliniM A, AydinA. Effect of faulting on fluid flow in porous sandstones: Petrophysical properties [J]. AAPG Bulletin, 1994, 78(3): 355-377

[7] BartonC A, ZobackM D, MoosD. Fluid flow along potentially active faults in crystalline rock [J]. Geology, 1995, 23(8): 683

[8] HeapM J, KennedyB M. Exploring the scale-dependent permeability of fractured andesite [J]. Earth & Planetary Science Letters, 2016, 447: 139-150

[9] RawlingG C, GoodwinL B, WilsonJ L. Internal architecture, permeability structure, and hydrologic significance of contrasting fault-zone types [J]. Geology, 2001, 29(1): 43-46

[10] SaulC J, EvansJ P, ForsterC B. Fault zone architecture and permeability structure [J]. Geology, 1996, 24(11): 1025-1028

[11] JiaC J, XuW Y, WangH L, WangR B, JunY U, YanL. Stress dependent permeability and porosity of low-permeability rock [J]. Journal of Central South University, 2017, 24(10): 2396-2405

[12] BraceW F. A note on permeability changes in geologicmaterial due to stress [J]. Pure and Applied Geophysics, 1978, 116(4): 627-633

[13] MorrowC A, LocknerD A. Permeability and porosity of the Illinois UPH 3 drillhole granite and a comparison with other deep drillhole rocks [J]. Journal of Geophysical Research Atmospheres, 1997, 1023067-3075

[14] ZhuW, WongT F. The transition from brittle faulting to cataclastic flow: Permeability evolution [J]. Journal of Geophysical Research Solid Earth, 1997, 102: 3027-3042

[15] SuriP, AzeemuddinM, ZamanM, KukretiA R, RoegiersJ C. Stress-dependent permeability measurement using the oscillating pulse technique [J]. Journal of Petroleum Science & Engineering, 1997, 17(34): 247-264

[16] DavidC, MenendezB, ZhuW, DavidC, MenendezB, ZhuW, WongT F. Mechanical compaction, microstructures and permeability evolution in sandstones * [J]. Physics & Chemistry of the Earth Part A: Solid Earth & Geodesy, 2001, 26(12): 45-51

[17] LiuZ B, ShaoJ F, HuD W, XieS Y. Gas permeability evolution with deformation and cracking process in a white marble under compression [J]. Transport in Porous Media, 2016, 111(2): 1-15

[18] ZengK, XuJ, HeP, WangC G. Experimental study on permeability of coal sample subjected to triaxial stresses [J]. Procedia Engineering, 2011, 26(1): 1051-1057

[19] XuP, YangS Q. Permeability evolution of sandstone under short-term and long-term triaxial compression [J]. International Journal of Rock Mechanics & Mining Sciences, 2016, 85: 152-164

[20] MitchellT M, FaulknerD R. Experimental measurements of permeability evolution during triaxial compression of initially intact crystalline rocks and implications for fluid flow in fault zones [J]. Journal of Geophysical Research-Solid Earth, 2008, 113: 226-227

[21] WangH, XuW, ShaoJ, SkoczylasF. The gas permeability properties of low-permeability rock in the process of triaxial compression test [J]. Materials Letters, 2014, 116(2): 386-388

[22] ChengC, ChenX, ZhangS. Multi-peak deformation behavior of jointed rock mass under uniaxial compression: Insight from particle flow modeling [J]. Engineering Geology, 2016, 213: 25-45

[23] FanX, KulatilakeP H S W, ChenX. Mechanical behavior of rock-like jointed blocks with multi-nonpersistent joints under uniaxial loading: A particle mechanics approach [J]. Engineering Geology, 2015, 190: 17-32

[24] YangS Q, HuangY H, JingH W, LiuX R. Discrete element modeling on fracture coalescence behavior of red sandstone containing two unparallel fissures under uniaxial compression [J]. Engineering Geology, 2014, 178(6): 28-48

[25] YangX X, KulatilakeP H S W, ChenX, JingH W, YangS Q. Particle flow modeling of rock blocks with nonpersistent open joints under uniaxial compression [J]. International Journal of Geomechanics, 2016, 16(6): 04016020

[26] HuangY H, YangS Q, ZengW. Experimental and numerical study on loading rate effects of rock-like material specimens containing two unparallel fissures [J]. Journal of Central South University, 2016, 2361474-1485

[27] YangX X, JingH W, ChenK F, YangS Q. Failure behavior around a circular opening in a rock mass with non-persistent joints: A parallel-bond stress corrosion approach [J]. Journal of Central South University, 2017, 24(10): 2406-2420

[28] ThallakS, RothenburgL, DusseaultMSimulation of multiple hydraulic fractures in a discrete element system [C]//Proceedings of the The 32nd US Symposium on Rock Mechanics, 1991, Oklahoma, F, Norman

[29] BrunoM S. Micromechanics of stress-induced permeability anisotropy and damage in sedimentary rock [J]. Mechanics of Materials, 1994, 18(1): 31-48

[30] Al-BusaidiA, HazzardJ F, YoungR P. Distinct element modeling of hydraulically fractured Lac du Bonnet granite [J]. Journal of Geophysical Research Solid Earth, 2005, 110: 351-352

[31] WangT, ZhouW, ChenJ, XiaoX, LiY, ZhaoX Y. Simulation of hydraulic fracturing using particle flow method and application in a coal mine [J]. International Journal of Coal Geology, 2014, 121: 1-13

[32] CundallP A, StrackO D L. A discrete numerical mode for granular assemblies [J]. Géotechnique, 1979, 29(1): 47-65

[33] ChoN, MartinC D, SegoD C. A clumped particle model for rock [J]. International Journal of Rock Mechanics & Mining Sciences, 2007, 44(7): 997-1010

[34] CundallP AFluid Formulation for PFC2D [M]. Minneapolis, 2000, USA: Itasca Consulting Group, MN

[35] HazzardJ F, YoungR P, OatesS JNumerical modelling of seismicity induced by fracture injections in a fractured reservoir [C]//Proceedings of the In Proceedings of the 5th North American Rock Mechanics Symposium Mining and Tunnel Innovation and Opportunity. Toronto, 2002, Canada, ON

[36] ZhaoX, PaulY R. Numerical modeling of seismicity induced by fluid injection in naturally fractured reservoirs [J]. Geophysics, 2011, 76(6): WC169

[37] ZhouJ, ZhangL, BraunA. Numerical modeling and investigation of fluid-driven fracture propagation in reservoirs based on a modified fluid-mechanically coupled model in two-dimensional particle flow code [J]. Energies, 2016, 99699

[38] PFC 5.0 manual [M].Minneapolis, 2015, USA: Itasca Consulting Group, MN

[39] DavyC A, SkoczylasF, BarnichonJ D, LebonP. Permeability of macro-cracked argillite under confinement: Gas and water testing [J]. Physics & Chemistry of the Earth Parts A/b/c, 2007, 328–14667-680

[40] JiangC L, QiangS, JiangZ Q, ZhuS Y. Permeability catastrophe of brittle rock during complete stress-strain path [J]. Zhongnan Daxue Xuebao, 2012, 43(2): 688-693

[41] MatthI S K, BelaynehM. Fluid flow partitioning between fractures and a permeable rock matrix [J]. Geophysical Research Letters, 2004, 31(7): 221-237

[42] LiuH L, YangT H, YuQ L. Experimental study on fluid permeation evolution in whole failure process of tuff [J]. Dongbei Daxue Xuebao/Journal of Northeastern University, 2009, 30(7): 1030-1033

[43] LionM, SkoczylasF, LedS B. Determination of the main hydraulic and poro-elastic properties of a limestone from Bourgogne, France [J]. International Journal of Rock Mechanics & Mining Sciences, 2004, 41(6): 915-925