Custom bit for Nipple Profile Milling leads to increased production

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JAL171264 Custom bit for nipple profile milling leads to increased production - Well Intervention - Welltec
  • Well type Oil Producer
  • Max. temperature 120ºC
  • Location Africa


A client in North Africa needed a milling solution for a completion restriction which was choking back production. The well was flowing at 1 m3/hr but was forecasted to produce at rates up to 15m3/hr. The client approached Welltec® for a solution to enlarge a 4145 steel (42Cr) nipple-like restriction from an inner diameter of 38mm to 60mm over a distance of 200mm. Previous solutions from other service providers, including a snubbing operation, had failed.

Welltec concluded that 4145 steel had not been previously milled with this type and size of bit. Following a detailed analysis, Welltec trimmed a 2.5″ NPR MMC bit down to 2.375″ (60 mm) and sent it to location.


Initially, a single Well Tractor® provided the weight on bit (WOB) for the Well Miller®, and yielded positive milling results; however, in light of operational limitations and analysis of real-time data, Welltec changed out the single Well Tractor for tandem tractors on the subsequent run. The tandem tractors maximized WOB, increased the rate of penetration (ROP) for milling, and easily met the forecasted operational time.

Total milling time was 13 hours, with an average ROP of 15.38 mm/hr.

A subsequent slickline drift/depth determination encountered no problems when passing through the now enlarged restriction from the upper to lower completion.


The operation was completed in 36 hours, without the use of a rig. The operation enabled the client to immediately increase production.

Welltec’s simple but innovative solution eliminated the need for a workover rig, reducing the client’s cost while helping yield the full value of their assets. Finally, the e-line solution reduced the complexity and hazard potential of the operation, thereby minimizing HSE risks.