Abstract

Temporary well isolation projects have been successfiilly performed using a non-formation damaging polymer plug and coiled tubing. Previously used conventional kill muds can cause severe formation damage, reducing productivity once the well is put back into production. Other concerns while performing workover operations include the stability of casing in older wells to support inflatable plugs and the entry size to expansion diameter required to set the packer in each well. Use of a crosslinked polymer plug in conjunction with coiled tubing achieved accurate placement while avoiding the problem of over displacement. The crosslinked polymer plug protected the formation while supporting the kill fluid allowing for multiple casing string top joints to be cut and welded, along with wellhead replacement to be accomplished.

A second application of this non-damaging temporary isolation plug has been to control sloughing shales. These shale fragments tend to bridge off on ledges located above gauge hole sections causing problems running and setting production casing through the caving are. The crosslinked polymer plug has been used to suspend the shale fragments allowing the casing packer to be un-set and lowered through the problem area without any problems.

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