Multiple Zone Completion
A multiple completion is one where we can produce several different reservoir zones through separate flow paths within the same wellbore. As we shall see, we may accomplish this with tubing/annulus flow, multiple tubing strings, or by cementing several independent tubing strings in the same wellbore (a multiple tubingless completion).

Reasons For Multiple Completions

A multiple completion is one where we can produce different reservoirs through separate flow paths within the same wellbore.
https://www.drillingmanual.com/multiple-zone-completion/