Qualification of Specialized Cement To Inflate Bridge Plug for Water Shutoff Application in Horizontal Wells
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.