What are the benefits and risks associated with underbalanced perforating prior to frac-packing?
Operators are faced with a choice of perforating overbalanced or underbalanced. Overbalanced perforating refers to the practice of perforating with the hydrostatic pressure of the completion fluid across the zone to be perforated. This is not extreme overbalanced perforating where the pressure across the perforated zone is increased to greater than the zones fracture pressure. Underbalanced perforating refers to the practice of reducing the hydrostatic pressure across the zone to be perforated from several hundred to several thousand pounds per square inch, psi. The underbalanced operation typically will consist of a controlled rate-volume flow back. The flow back volume will be several barrels of fluid, to a workstring volume or to even a well test depending on the operators’ requirements. Underbalanced perforating is performed to help clean up perforation tunnels by creating a differential pressure sufficient to pull and remove the compacted and damaged zone from the perforation tunn
