Article: Underbalance perforation!

[eldar]

You can view the page at

[link Point to another website Only the registered members can access]

[Damir]

Overbalanced perforation means that mud pressure in well bore is higher than pressure in reservoir, when you perforate mud enters in perforations and you have invasion. Underbalanced means that mud pressure is below reservoir pressure, so when you perforate reservoir fluid enters well bore, and there is no invasion in near wellbore area.