Simulation of hydraulic fracturing processes combining finite elements and lattice Boltzmann methods

Simulation of hydraulic fracturing processes combining finite elements and lattice Boltzmann methods

Camones, Luis A. Mejia; Vargas Jr., E.; Velloso, R.; Paulino, G. H.

Abstract:

This research addresses hydraulic fracturing or hydro-fracking, i.e. fracture propagation process in rocks through the injection of a fluid under pressure, which generates cracks in the rock that propagate according to the amount of fluid injected. This technique leads to an increase of the permeability of the rock mass and, consequently, improve oil production. Several analytical and numerical models have been proposed to study this fracture mechanism, generally based in continuum mechanics or using interface elements through a known propagation path. In this work, the crack propagation is simulated using the PPR potential-based cohesive zone model [1,2] by means of an extrinsic implementation. Thus, interface cohesive elements are adaptively inserted in the mesh to capture the softening fracture process. The fluid pressure is simulated using the lattice Boltzmann model [3] through an iterative procedure. The boundaries of the crack, computed using the finite element method, are transferred to the lattice Bolztmann model as boundary conditions, where the force applied on these boundaries, caused by the fluid pressure, can be calculated. These forces are then transferred to the finite element model as external forces applied on the faces of the crack. The new position of the crack faces is then calculated and transferred to the lattice Boltzmann model to update the boundary conditions. This feedback-loop for fluid-structure interaction allows modeling of hydraulic fracturing processes for irregular path propagation. Examples will be provided to demonstrate the features of the proposed methodology.

This research addresses hydraulic fracturing or hydro-fracking, i.e. fracture propagation process in rocks through the injection of a fluid under pressure, which generates cracks in the rock that propagate according to the amount of fluid injected. This technique leads to an increase of the permeability of the rock mass and, consequently, improve oil production. Several analytical and numerical models have been proposed to study this fracture mechanism, generally based in continuum mechanics or using interface elements through a known propagation path. In this work, the crack propagation is simulated using the PPR potential-based cohesive zone model [1,2] by means of an extrinsic implementation. Thus, interface cohesive elements are adaptively inserted in the mesh to capture the softening fracture process. The fluid pressure is simulated using the lattice Boltzmann model [3] through an iterative procedure. The boundaries of the crack, computed using the finite element method, are transferred to the lattice Bolztmann model as boundary conditions, where the force applied on these boundaries, caused by the fluid pressure, can be calculated. These forces are then transferred to the finite element model as external forces applied on the faces of the crack. The new position of the crack faces is then calculated and transferred to the lattice Boltzmann model to update the boundary conditions. This feedback-loop for fluid-structure interaction allows modeling of hydraulic fracturing processes for irregular path propagation. Examples will be provided to demonstrate the features of the proposed methodology.

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Referências bibliográficas

• [1] K. Park, G. H. Paulino, 2012. Computational implementation of the PPR potential-based cohesive model in ABAQUS: Educational perspective, Engineering Fracture Mechanics, 93, 239-262.
• [2] K. Park, G. H. Paulino, J. Roesler, 2009. A unified potential-based cohesive model of mixed mode fracture, Journal of the Mechanics and Physics of Solids, 57, 891-908.
• [3] R. Velloso, 2010. Numerical analysis of fluid mechanical coupling in porous media using the discrete element method, PhD dissertation, Pontifical Catholic University of Rio de Janeiro (in Portuguese).

Como citar:

Camones, Luis A. Mejia; Vargas Jr., E.; Velloso, R.; Paulino, G. H.; "Simulation of hydraulic fracturing processes combining finite elements and lattice Boltzmann methods", p-84-84. In: Proceedings of the 13th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials [=Blucher Material Science Proceedings, v.1, n.1]. São Paulo: Blucher, 2014.
ISSN 23589337, DOI