1. Frr = residual resistance factor
  2. h = height, ft [m]
  3. k = permeability, darcys [mm2]
  4. kgas = permeability to gas, darcys [mm2]
  5. ko = permeability to oil, darcys [mm2]
  6. kw = permeability to water, darcys [mm2]
  7. L = distance along a fracture, ft [m]
  8. Lgel = distance of gel penetration along a fracture, ft [m]
  9. Lf = fracture length, ft [m]
  10. Δp = pressure drop, psi [Pa]
  11. Δpgel = pressure drop during gel injection, psi [Pa]
  12. Δpwater = pressure drop during water injection, psi [Pa]
  13. dp/dl = pressure gradient, psi/ft [Pa/m]
  14. q = total injection or production rate, BPD [m3/d]
  15. re = external drainage radius, ft [m]
  16. rgel = radius of gel penetration, ft [m]
  17. rw = wellbore radius, ft [m]
  18. Sor = residual oil saturation
  19. t = time, days
  20. wf = fracture width, in. [m]
  21. μ = viscosity, cp [mPa-s]