Cement plug setting is one of the most unpredictable and time consuming operations in the drilling process of a geothermal well, thus adding considerable cost and risk to drilling, completion, and workover operations. Setting of ten to twenty consecutive plugs for a single sidetracking job, each requiring up to 8 hours of wait time for the cement to cure, are not unheard of in the industry. Significant risk arises from the inability to support the cement slurry while it cures inside the wellbore.
Perigon’s cement support tool (CST™) was designed to increase the success rate of setting cement plugs by physically separating the plug from the drilling fluid while the slurry cures, just as if it was set at the bottom of a well or above a bridge plug. Another attractive feature of the CST™ tool is its drillability, and foldable aluminum and composite construction (Harestad, 2015), which enables it to be pumped through small diameter tubing and then enlarged in the well bore. This paper summarizes a recent, first-ever and successful plug setting operation using coiled tubing in a large diameter geothermal well casing.