In mature oil and gas fields, excess water production often threatens the economic viability of a well. Excess water production can cause an increase in production cost and a decrease in productivity. Moreover, in an offshore environment, this water creates a burden in terms of the treatment facilities and the increased disposal cost.

There are different techniques and fluids that are used today for water shutoff. One of the techniques is wireline dump bailers used with cement, but this technique cannot be used in horizontal wells because of wireline limitations. To counter that, the industry witnessed the development of a "reservoir carrying fluid" that can be used with coiled tubing (CT) in horizontal wells for water shutoff.

Water or glycol can be used to inflate the plug to enable the rubber elements to conform to the setting inside diameter (ID) in which it is being conveyed. However, using these fluids means that long-term isolation is compromised. To accomplish long-term isolation, the inflation of the system must be done using a specialized sealant.

An operator in the North Sea interested in the technique asked a service company to provide a cementing solution to the system. This paper describes the different stages of this qualification process including the laboratory procedures that have been developed especially for this application, explains the sealant selection criteria and the field qualification of both the CT cement-filled reservoir and the specialized expanding cement slurry, and, finally, reviews a case history.

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