Underbalance perforation!

[eldar]

What is difference between underbalance and overbalance perforation in TCP?

[barryn56]

Underbalance refers to the wellbore pressure being lower than the formation pressure of the zone(s) being perforated. Overbalance is the opposite - a higher pressure in the wellbore than the reservoir zones. A high underblaace is expected to cause the zones to flow immediately after perforating, providing a clean up. However, in friable formations, they may fail, causing the guns to be sanded in. In these, and other, situations, a high overbalance with a clean fluid can provide a local fracturing effect after perforating, with high injection rates.