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Multiple zone completion is one type of completion which allows operators to selectively produce or comingle reservoir fluid from different zones into one well. It is also possible to workover the upper part of completion string without removing the next interval completion. Additionally, through tubing perforation is can performed at the bottom zone. A multiple zone completion can be divided into two parts, which are single string completion and multiple string completion.
Single zone completion is one of the types of upper completion which allows producing only one zone. Production tubing is a flow path for fluid from a reservoir to flow to the surface so it protects the casing from corrosion and maximizes the efficiency of the flow.
In a single tubing string completion, typically a packer is set on top of a reservoir so the reservoir fluid can flow up into the production tubing. Types of packers are based on several factors as temperature, pressure, reservoir fluid, etc. Additionally, complexity of tubing and packer installation is driven by objectives.
Cased and perforated completion is the most common type of completion which is selected my many companies. For this completion, a production casing or a liner is cemented through reservoir zone(s) and subsequently, a well is perforated in order to provide communication between the formation and wellbore.
Perforation should ideally penetrate deeper rather than nearer a wellbore damage zone around a wellbore so fluid from a reservoir can effectively flow into a wellbore. Additionally, several depth control methods help to accurately select which section of reservoir to be perforated. Hence, undesired zones, such as gas, water or weak formation can be avoided and this will improve well production efficiency.
Cementing around the wellbore is one of the critical parts for this completion because good cement will effectively isolate all zones and allows a wellbore to produce from several zones without communication between reservoirs. Moreover, packers are run into a wellbore to isolate reservoir fluid when it flows into a wellbore.
Another important feature of this completion is the ability to selectively produce or inject into any reservoir. A sliding sleeve on each zone can be opened and closed to allow selective production or injection operation. Figure 1 illustrates the diagram of cased and perforated completion.
Figure 1- Example of Cased and Perforated Schematic