Corrosion of injection equipment is a common problem in CO2 miscible injection operations. The two basic mechanisms by which this corrosion occurs are from internal corrosion caused by holidays in the injection tubing coating as well as from external corrosion caused by CO2 invading the tubing-casing annulus through minute seepages in the downhole injection equipment.

Unfortunately, these problems are both common and costly.

In one West Texas CO2 injection project, Unocal Corporation, using state of the art connection and testing procedures has developed a method of installing downhole CO2 injection equipment which virtually eliminates this tubing-casing communication. In addition, the internal plastic coating of the tubulars remains intact and holiday free during field handling procedures. The system involves the use of a helium connection test combined with meticulous attention to detail in the field handling and connection of the tubulars.

The following is a discussion of the development of these procedures.

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