Fully coupled thermo-hydro-mechanical model for fracture propagation in leak-off dominated regimes

  • Rueda, Julio (Tecgraf Institute/PUC-Rio)
  • Mejia, Cristian (Tecgraf Institute/PUC-Rio)
  • Roehl, Deane (Pontifical Catholic University of Rio de Jane)
  • Firme, Pedro (Tecgraf Institute/PUC-Rio)

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Hydraulic fracturing is the process of injecting fluid at high pressure to induce fracture propagation in a rock formation. This technique is commonly used to enhance permeability and well-reservoir connectivity, increasing fluid flow and heat transfer in oil/gas/geothermal reservoirs [1]. Analytical [2–4] and numerical [5–7] solutions have been proposed for predicting the evolution of induced fluid-driven fracture propagation. However, most solutions neglect the fluid-induced thermal effects within the porous medium and the induced fractures [8,9]. This work proposes a fully coupled thermo-hydro-mechanical (THM) finite element model to study fluid-driven fracture propagation. The proposed model considers poroelasticity, fluid flow, convection/diffusion heat transfer within the permeable rock formation, and induced fracture under single-phase fluid flow conditions. Interface elements with a cohesive zone model (CZM) are used to simulate fluid-driven fractures. The fluid flow inside the fracture channels follows the transition from Darcy flow to Poiseuille flow (parallel plate) as damage in the element initiates and evolves. The numerical results are compared against related analytical and numerical solutions. In general, good performance of the proposed method in the analyzed cases is observed. The influence of cold fluid injection under leak-off-toughness and leak-off-viscosity-dominated regimes is also investigated. The numerical results show that initial stresses, injection period, and heat transfer significantly impact the fracture geometry and fluid pressure. Compared with hydromechanical models, high initial stresses reduce fluid pressure inside the fracture and fluid leak-off to the surrounding media, increasing fracture opening and length. This behavior can be related to THM coupling effects within the porous medium. Finally, the study provides valuable insights to understand the complex hydraulic fracturing process better, considering thermal, hydraulic, and mechanical coupling behaviors. REFERENCES [1] Guo T, Gong F, Wang X, Lin Q, Qu Z, Zhang W. Performance of enhanced geothermal system (EGS) in fractured geothermal reservoirs with CO2 as working fluid. Appl Therm Eng 2019;152:215–30. [2] Adachi JI, Detournay E. Self-similar solution of a plane-strain fracture driven by a power-law fluid. Int J Numer Anal Methods Geomech 2002;26:579–604. [3] Bunger AP, Detou