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Modeling of Hydraulic Fracture Propagation in Naturally Fractured Saturated Poruos Media Using the XFEM Method

Hirmand, Mohammad Reza | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45433 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. Hydraulic fracture propagation occures in fractured saturated porous media due to fluid leakage from the crack faces and the consequent fluid pressure. In many cases, hydraulic fracturing may be considered as a detrimental phenomenon which endangers stability of human made structures like rock-fill dames. However, in recent decades the hydraulic fracturing has been an appealing method for increasing the production rate of low-permeability oil and gas reservoirs in petroleum industries.
    In order to efficiently assess the behavior of saturated madia one needs to consider the coupling between the solid and fluid phases of the medium. To do so, the coupled formulation refered to as u-p formulations are usually considered to study the behavior of the porous medium. Apart from this, the naturally existing fractures have considerable effects on the behavior of porous media. The interaction between hydraulically driven fractures and pre-existing natural faults induces opened and closed zones on these faults which in turen affect the hydraulic fracture behavior. Such an extremely complex phenomenon neccisiates to adopt an efficient numerical model. In the present investigation, the governing equations of the porous media together with the weak form and resulting matrix equations are presented in the framework of the eXtended Finite Element Method (XFEM). Also, the algorithms of modelling the frictional contact condition together with the cohesive crack growth have been presented. The presented formulations have then been utilized to investigate the behavior of haydraulic fracturing in naturally fractured saturated porous reservoirs. Several examples studied in this work indicate that the interaction of a hydraulically drivenen fracture and a natural fault depends upon different conditions including the inclination angle of the natural fault, boundary conditions, shear strength of the natural faults and in situ stresses which in turn result in four different conditions of hydraylic fracture arrest, diversion, penetration and offset
  9. Keywords:
  10. Saturated Porous Medium ; Hydraulic Fracturing ; Extended Finite Element Method ; Natural Fault ; Multiple Crack

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