World’s first nipple milling with 2 1/8” tools

When an operator in the North Sea experienced problems running a 2 1/2” inflatable plug through a Baker “F” nipple profile with an internal diameter (ID) of 2.562” in a producing well, offshore Norway, Welltec proposed a solution utilizing two custom milling bits.

System Integration Testing was conducted to establish operating procedure, determine the suitable bit design and optimum weight on bit (WOB) needed for this world’s first operation.

Two bits, consisting of a unique Metal Matrix Compound (MMC), were manufactured for this specific operation, 2.677” and 2.638” respectively, to grind through the nipple profile leaving the surface smooth to ease further interventions. They were designed so that if the first bit wore down before the nipple was milled through, the second bit could pass through the milled section and finish the job without getting stuck.

No restrictions were found in the well down to the nipple depth and a toolstring consisting of the Well Miller® NPR with the custom 2.677” milling bit was run in hole. After about two hours of effective milling time, the power consumption changed and the tool was returned to surface, where the milling bit did not show significant wear. The toolstring returned into the well with the same bottom hole assembly (BHA) configuration. On this run it passed through the nipple profile without problems. Several more passes were made to confirm depth and easy to pass through.

In a few short days, using only e-line equipment the operator was able to remove the restriction, set a straddle packer and restore the well to production; without the use of a workover rig or CT unit.

To read more about this operation, please see the full case story, or read more on Welltec’s Milling Solutions in our brochure.