Numerical Assessment of the Maximum Operating Pressure for SAGD Projects Considering the Effects of Anisotropy and Natural Fractures

• Author(s) / Creator(s)

  • Ehsan Rahmati
  • Alireza Nouri
  • Vahidoddin Fattahpour
  • Japan Trivedi

• There has been an increasing awareness of the importance of caprock integrity during Steam
  Assisted Gravity Drainage (SAGD) operations. However, mathematical tools that have been
  developed for caprock integrity studies have not incorporated an important characteristic of cap
  shales, which is the intrinsic anisotropy and structural anisotropy caused by the natural fractures
  (NFs) in the cap shale. This paper addresses the effects of the intrinsic anisotropy of the shales
  and also the existence of NFs on the Maximum Operating Pressure (MOP) in SAGD projects.
  In this study, a new constitutive model is developed and incorporated to consider the effect of
  NFs and intrinsic anisotropy in the cap shale. A coupled numerical tool was utilized to determine
  the MOP for different case scenarios in the number of fracture sets, fracture density and dip
  angle, as well as the height. Results of all cases were analyzed to evaluate their effect on the
  MOP.
  Results of the coupled model indicate continued integrity of the caprock for the case study
  project for the current operational program for almost all the considered case scenarios, except
  for an extreme case. Therefore, higher injection pressures than the current pressure were
  investigated to assess the MOP. Results indicate that the MOP was highly sensitive to the
  fracture density, direction, and height. Results also display a minor impact for the horizontal
  fractures on the MOP for the case study while fractures with the dip angle between 25° to 65°
  show a significant impact on the caprock integrity, hence, the MOP. Moreover, results indicate
  an overestimation of the MOP by up to 23% when neglecting the NFs. Comparing the results of
  different case scenarios with those of conventional isotropic models highlights the requirement to
  include the effect of NFs in caprock integrity studies.

• Date created

  2017-01-01

• Subjects / Keywords

  • SAGD
  • Maximum Operation Pressure (MOP)
  • Natural fractures
  • Shale
  • Caprock integrity
  • Anisotropy
  • Coupled numerical modeling

• Type of Item

  Article (Draft / Submitted)

• DOI

  https://doi.org/10.7939/r3-2wse-r070

• License

  Attribution-NonCommercial 4.0 International