A dually completed well is a well completed to produce from two separate pay zones. The zones are separated by tubing packers in the well and the oil and gas is brought up the well in separate strings of tubing and stored in separate tanks.
One well can produce from two or more producing zones in a multiple completion. If there are two producing zones, two packers and two tubing strings are used in a dual completion. Sometimes only one packer and tubing string is used in a dual completion, and the production from one zone is brought up the casing-tubing annulus.