Investigating Stress Concentrations near Boreholes in Anisotropic Formations and the Mechanical Behavior of Drilling-induced Tensile Fractures

  • Author / Creator
    Jia, Qing
  • With the increasing exploitation of unconventional reservoirs, the demands of implementing geomechanics to improve the exploration and development process have been greater than before. Knowledge of in-situ stresses and rock failure mechanisms is key for building a comprehensive geomechanical model. Consequently, it is necessary to evaluate the state of stress in the Earth in order to design and efficiently operate engineered geothermal systems. The goal of this study is to investigate the variations of near-wellbore stress concentrations as a function of formation anisotropy, stress regimes and borehole relative orientations with respect to the in-situ stress, and then further examine the mechanical behavior of drilling induced tensile fractures. This is done by developing various MATLAB based analytical programs, creating numerical models and conducting lab simulations. Results from analytical models demonstrate that effects of formation anisotropy on borehole stress rise with increasing degree of anisotropy and the drilling-induced tensile fractures are not symmetrical when the borehole axis is not aligned with any of the in-situ stresses. Those models can also be integrated with different industry data sets to estimate the stress states in the formation of interest and enable us have better insights for drilling optimization, hydraulic fracturing design, completion planning and production maximization. Moreover, in the lab, both axial and en echelon drilling-induced tensile fractures were generated and their failure mechanisms agree with the general theory. Numerical models are not fully completed as the final goal is to develop a dynamic 3-D model based upon the current static model to simulate the lab processes in real-time.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Physics
  • Specialization
    • geophysics
  • Supervisor / co-supervisor and their department(s)
    • Schmitt, Douglas R. (Department of Physics)
  • Examining committee members and their departments
    • Schmitt, Douglas R. (Department of Physics)
    • Derek Apel (Department of Civil and Environment Engineering)
    • Currie, Claire (Department of Physics)
    • Meldrum, Al (Department of Physics)