Transport efficiency and dynamics of hydraulic fracture networks

Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/fα behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

[1]  M. Jébrak,et al.  Polyphase hydrothermal breccias associated with unconformity-related uranium mineralization (Canada): from fractal analysis to structural significance , 2002 .

[2]  R. Sibson.  Brecciation processes in fault zones: Inferences from earthquake rupturing , 1986 .

[3]  A. Nur,et al.  Permeability as a toggle switch in fluid-controlled crustal processes , 2000 .

[4]  Agust Gudmundsson,et al.  Propagation pathways and fluid transport of hydrofractures in jointed and layered rocks in geothermal fields , 2002 .

[5]  M. Gölke,et al.  Finite-element modelling of the structure and evolution of the South Kenya Rift, East Africa , 1994 .

[6]  C. Passchier,et al.  Shear sense indicators in striped bedding-veins , 2000 .

[7]  N. Tsuchiya,et al.  Velocity of vertical fluid ascent within vein-forming fractures , 2009 .

[8]  Rajat Gupta,et al.  Applied Hydrogeology of Fractured Rocks , 1999 .

[9]  W. Brace.  Permeability of crystalline and argillaceous rocks , 1980 .

[10]  R. Powell,et al.  The role of exhumation in metamorphic dehydration and fluid production , 2010 .

[11]  Agust Gudmundsson,et al.  Rock Fractures in Geological Processes: Index , 2011 .

[12]  Y. Podladchikov,et al.  Compaction-driven fluid flow in viscoelastic rock , 1998 .

[13]  P. Laznicka.  Breccias and ores. Part 1: History, organization and petrography of breccias , 1989 .

[14]  Zheming Zhu,et al.  Evaluation of the range of horizontal stresses in the earth's upper crust by using a collinear crack model , 2013 .

[15]  John G. Ramsay,et al.  The crack–seal mechanism of rock deformation , 1980, Nature.

[16]  G. Manger,et al.  Porosity and bulk density of sedimentary rocks , 1963 .

[17]  T. Driesner,et al.  Is the Mount Isa copper deposit the product of forced brine convection in the footwall of a major reverse fault , 2004 .

[18]  J. Weertman.  Theory of water-filled crevasses in glaciers applied to vertical magma transport beneath oceanic ridges , 1971 .

[19]  Paul D. Bons,et al.  New experiment to model self-organized critical transport and accumulation of melt and hydrocarbons from their source rocks , 2001 .

[20]  J. Olson,et al.  Coevolution of crack-seal texture and fracture porosity in sedimentary rocks: cathodoluminescence observations of regional fractures , 2004 .

[21]  E. Gomez‐Rivas,et al.  A review of the formation of tectonic veins and their microstructures , 2012 .

[22]  P. Bons,et al.  Hydrothermal vein formation by extension-driven dewatering of the middle crust: An example from SW Germany , 2009 .

[23]  Yongzhao Zhan,et al.  Maximum Neighborhood Margin Discriminant Projection for Classification , 2014, TheScientificWorldJournal.

[24]  Zhenjun Yang,et al.  Simulation of hydraulic fracturing in rock mass using a smeared crack model , 2014 .

[25]  Valentin Gischig,et al.  Development of connected permeability in massive crystalline rocks through hydraulic fracture propagation and shearing accompanying fluid injection , 2015 .

[26]  Haakon Fossen,et al.  Structural Geology: Glossary , 2010 .

[27]  C. Fowler,et al.  The Solid Earth: An Introduction to Global Geophysics , 1990 .

[28]  T. Dahm.  On the shape and velocity of fluid‐filled fractures in the Earth , 2000 .

[29]  N. Woodcock,et al.  Quantifying fault breccia geometry : Dent Fault, NW England , 2008 .

[30]  Colin W. Devey,et al.  Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges , 2014, Nature.

[31]  J. H. Kruhl,et al.  Repeated hydrothermal quartz crystallization and cataclasis in the Bavarian Pfahl shear zone (Germany) , 2014 .

[32]  T. Baker,et al.  Granite-related overpressure and volatile release in the mid crust: fluidized breccias from the Cloncurry District, Australia , 2006 .

[33]  Lan Ren,et al.  Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism , 2014, TheScientificWorldJournal.

[34]  D. Wiltschko,et al.  Fault controlled sequential vein dilation: competition between slip and precipitation rates in the Austin Chalk, Texas , 2000 .

[35]  E. Gomez‐Rivas,et al.  Fluid mixing from below in unconformity-related hydrothermal ore deposits , 2014 .

[36]  P. Blum,et al.  The Jabal Akhdar dome in the Oman Mountains: Evolution of a dynamic fracture system , 2014, American Journal of Science.

[37]  C. Teyssier,et al.  Isotope transport and exchange within metamorphic core complexes , 2007, American Journal of Science.

[38]  E. Hering,et al.  Physik für Ingenieure , 1997 .

[39]  H. Horii,et al.  Micromechanics-based continuum model for hydraulic fracturing of jointed rock masses during HDR stimulation , 1998 .

[40]  Yang Li,et al.  Simulation of hydraulic fracturing using particle flow method and application in a coal mine , 2014 .

[41]  Renaud Toussaint,et al.  Dynamic Development of Hydrofracture , 2013, Pure and Applied Geophysics.

[42]  E. Majer,et al.  Studying hydrofractures by high frequency seismic monitoring , 1986 .

[43]  H. Schmeling,et al.  Rift induced delamination of mantle lithosphere and crustal uplift: a new mechanism for explaining Rwenzori Mountains’ extreme elevation? , 2010 .

[44]  P. Bons,et al.  Crustal-scale folding: Palaeozoic deformation of the Mt Painter Inlier, South Australia , 2013 .

[45]  D. Maugis.  Contact, Adhesion and Rupture of Elastic Solids , 2000 .

[46]  Hisao Ito,et al.  Grain size distributions of fault rocks: A comparison between experimentally and naturally deformed granitoids , 2007 .

[47]  P. Bons,et al.  Long-lived crustal-scale fluid flow: the hydrothermal mega-breccia of Hidden Valley, Mt. Painter Inlier, South Australia , 2013, International Journal of Earth Sciences.

[48]  M. Jébrak,et al.  Hydrothermal breccias in vein-type ore deposits: A review of mechanisms, morphology and size distribution , 1997 .

[49]  Arno Zang,et al.  Stress Field of the Earth's Crust , 2010 .

[50]  Md. Mofazzal Hossain,et al.  Numerical simulation of complex fracture growth during tight reservoir stimulation by hydraulic fracturing , 2008 .

[51]  Y. Podladchikov,et al.  A Hydromechanical Model for Lower Crustal Fluid Flow , 2013 .

[52]  Panos Papanastasiou,et al.  A coupled elastoplastic hydraulic fracturing model , 1997 .

[53]  P. Eichhubl,et al.  Rates of fluid flow in fault systems; evidence for episodic rapid fluid flow in the Miocene Monterey Formation, coastal California , 2000 .

[54]  Owen M. Phillips,et al.  Geological Fluid Dynamics: Sub-surface Flow and Reactions , 2009 .

[55]  J. Nunn.  Buoyancy-driven propagation of isolated fluid-filled fractures: Implications for fluid transport in Gulf of Mexico geopressured sediments , 1996 .

[56]  Alan R. Huffman,et al.  Pressure regimes in sedimentary basins and their prediction : an outgrowth of the international forum sponsored by the Houston chepter of the American Association of Drilling Engineers, Houston, Texas, September 2-4, 1998 , 2001 .