Hydro-mechanical coupled mechanisms of hydraulic fracture propagation in rocks with cemented natural fractures

Abstract Natural fractures commonly exist in unconventional reservoirs such as shale and tight gas sandstone, which are mostly cemented (or sealed) with minerals and not able to contribute to reservoir storage or rock permeability. However, during hydraulic fracture stimulation, these cemented natural fractures will be encountered and influence hydraulic fracture geometry greatly and, thereby, gas production. In this work, hydraulic fracture propagation in rock with cemented natural fracture is investigated using our recently developed and validated hydro-mechanical coupled LBM-DEM model. The numerical results show that both the strength ratio (between cemented natural fracture and host rock) and the approach angle (between hydraulic and cemented natural fracture) significantly affect the hydraulic fracture propagation. A larger strength contrast or a smaller approach angle will be more conducive to deflection, which is consistent with experimental observation. For rocks with weakly cemented natural fractures, deflection is mainly caused by shear failure in weakly cemented fracture. However, for rocks with strongly cemented natural fractures, deflection happens accompanying with tensile failure in host rock along the cement wall, which cannot be captured by the previous numerical models where the cemented natural fracture is treated as a bonded interface. In addition, complex fracture network is more easily formed if multiple weakly cemented natural fractures are orthogonal to the hydraulic fracture propagation direction.

[1]  Ling Li,et al.  Breaking processes in three-dimensional bonded granular materials with general shapes , 2012, Comput. Phys. Commun..

[2]  W. Sassi,et al.  Natural sealed fractures in mudrocks: A case study tied to burial history from the Barnett Shale, Fort Worth Basin, Texas, USA , 2014 .

[3]  Sergio Andres Galindo-Torres,et al.  A coupled Discrete Element Lattice Boltzmann Method for the simulation of fluid-solid interaction with particles of general shapes , 2013 .

[4]  J. Olson,et al.  Natural fractures in shale: A review and new observations , 2014 .

[5]  Yu-Shu Wu,et al.  CO2 injection-induced fracturing in naturally fractured shale rocks , 2017 .

[6]  Benjamin Koger Cook,et al.  A coupled fluid–solid model for problems in geomechanics: Application to sand production , 2011 .

[7]  T. L. Blanton,et al.  An Experimental Study of Interaction Between Hydraulically Induced and Pre-Existing Fractures , 1982 .

[8]  Xiaowei Weng,et al.  Hydraulic Fracture Crossing Natural Fracture at Nonorthogonal Angles: A Criterion and Its Validation , 2012 .

[9]  N. Pan,et al.  Effective gas diffusion coefficient in fibrous materials by mesoscopic modeling , 2017 .

[10]  Moran Wang,et al.  Pore-scale geometry effects on gas permeability in shale , 2016 .

[11]  D. Elsworth,et al.  Types, characteristics and effects of natural fluid pressure fractures in shale: A case study of the Paleogene strata in Eastern China , 2016 .

[12]  B. Cook,et al.  Three‐dimensional immersed boundary conditions for moving solids in the lattice‐Boltzmann method , 2007 .

[13]  Shiyi Chen,et al.  LATTICE BOLTZMANN METHOD FOR FLUID FLOWS , 2001 .

[14]  Jianying Zhang,et al.  Lattice Boltzmann modeling for multiphase viscoplastic fluid flow , 2016 .

[15]  Norman R. Warpinski,et al.  Influence of Geologic Discontinuities on Hydraulic Fracture Propagation (includes associated papers 17011 and 17074 ) , 1984 .

[16]  Shiyi Chen,et al.  Mesoscopic predictions of the effective thermal conductivity for microscale random porous media. , 2007, Physical review. E, Statistical, nonlinear, and soft matter physics.

[17]  J. R. Torczynski,et al.  A Lattice-Boltzmann Method for Partially Saturated Computational Cells , 1998 .

[18]  David D. Pollard,et al.  An experimentally verified criterion for propagation across unbounded frictional interfaces in brittle, linear elastic materials , 1995 .

[19]  Christopher A. Wright,et al.  Integrating Fracture Mapping Technologies to Optimize Stimulations in the Barnett Shale , 2002 .

[20]  Jon E. Olson,et al.  The interaction of propagating opening mode fractures with preexisting discontinuities in shale , 2015 .

[21]  Yu Chen,et al.  Bonding Strength Effects in Hydro-Mechanical Coupling Transport in Granular Porous Media by Pore-Scale Modeling , 2016, Comput..

[22]  Stephen E. Laubach,et al.  Predicting and characterizing fractures in dolostone reservoirs: using the link between diagenesis and fracturing , 2004, Geological Society, London, Special Publications.

[23]  Jon E. Olson,et al.  Examining Hydraulic Fracture: Natural Fracture Interaction in Hydrostone Block Experiments , 2012 .

[24]  János Urai,et al.  Extension fracture propagation in rocks with veins: Insight into the crack‐seal process using Discrete Element Method modeling , 2013 .

[25]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[26]  N. Pan,et al.  Predictions of effective physical properties of complex multiphase materials , 2008 .

[27]  S. Laubach,et al.  Laurentian palaeostress trajectories and ephemeral fracture permeability, Cambrian Eriboll Formation sandstones west of the Moine Thrust Zone, NW Scotland , 2009, Journal of the Geological Society.

[28]  Moran Wang,et al.  Pore‐scale modeling of hydromechanical coupled mechanics in hydrofracturing process , 2017 .

[29]  J. Olson,et al.  Interaction analysis of propagating opening mode fractures with veins using the Discrete Element Method , 2016 .

[30]  David J. Sanderson,et al.  Numerical study of fluid flow of deforming fractured rocks using dual permeability model , 2002 .

[31]  X. Weng,et al.  Modeling of Hydraulic Fracture Network Propagation in a Naturally Fractured Formation , 2011 .

[32]  J. Olson,et al.  Examining the Geomechanical Implicaitons of Pre-Existing Fractures and Simultaneous-Multi-Fracturing Completions on Hydraulic Fractures: Experimental Insights into Fracturing Unconventional Formations , 2016 .

[33]  R. P. Young,et al.  Distinct element modeling of hydraulically fractured Lac du Bonnet granite , 2005 .

[34]  Julia F. W. Gale,et al.  Natural fractures in some US shales and their importance for gas production , 2010 .

[35]  J. Urai,et al.  The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing , 2014 .

[36]  Jon E. Olson,et al.  Examining the Effect of Cemented Natural Fractures on Hydraulic Fracture Propagation in Hydrostone Block Experiments , 2012 .

[37]  Ted Urbancic,et al.  Microseismic Imaging of Hydraulic Fracture Complexity in the Barnett Shale , 2002 .

[38]  Michael J. Mayerhofer,et al.  What Is Stimulated Reservoir Volume , 2010 .

[39]  Julia F. W. Gale,et al.  Natural fractures in the Barnett Shale and their importance for hydraulic fracture treatments , 2007 .

[40]  David J. Williams,et al.  A calibration methodology to obtain material parameters for the representation of fracture mechanics based on discrete element simulations , 2017 .