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 String Configuration
In a single string completion, a packer will be set above each zone in order to isolate fluid from each zone. What’s more, a packer will prevent corrosion in the production casing due to the flow of reservoir fluid. Figure 1 demonstrates an example of a single string configuration
A multiple-string configuration consists of two or more completion strings in one well. This is more expensive and complicated to install than a single-string configuration. However, it has some advantages such as the ability to simultaneous produce and injec into different zones and has a more accurate production allocation than a single string type.
Nowadays, single string completions are preferred to multiple string completions because of several issues as listed below;
- Less expensive
- Easier to install and workover
- Size of a production string in a single string is typically bigger than a multiple string at the same production casing size.
- Less complications for well control equipment
Jonathan Bellarby, 2009. Well Completion Design, Volume 56 (Developments in Petroleum Science). 1 Edition. Elsevier Science.
Wan Renpu, 2011. Advanced Well Completion Engineering, Third Edition. 3 Edition. Gulf Professional Publishing.
Ted G. Byrom, 2014. Casing and Liners for Drilling and Completion, Second Edition: Design and Application (Gulf Drilling Guides). 2 Edition. Gulf Professional Publishing.