Flapper valve milling with new star bit in high-temperature gas well

Hostile environment
JTN154167 First ever flapper valve milling - Well Intervention - Welltec
  • Well type Gas
  • Max. temperature 160ºC


A high-temperature gas well, offshore North Africa, experienced a malfunctioning downhole flapper valve preventing the client from re-perforating a lower zone. The well presented several downhole environmental challenges, including temperatures in excess of 160°C, high levels of CO2, and H2S.

Welltec® has successfully completed similar jobs in the region in the past, and the client identified the value of Welltec’s recently developed star bit, which minimizes flapper debris created during milling. Moreover, this operation required Welltec to conduct the operation jointly with the local e-line provider.


The Well Tractor® conveyed the toolstring to the flapper valve. The Well Miller®, equipped with the new star bit, was then engaged and milled through the flapper valve in just one hour. A second milling run verified that the milling bit penetrated the entire valve.

Once the successful flapper valve milling was verified, the Well Stroker® was used to set a Welltec Assurance Access Sleeve (WAAS) across the milled flapper assembly. The WAAS enables clients to gain easy entry and re-entry through the valve. The Well Stroker sets the WAAS via a stroke-up sequence. The Well Stoker successfully installed the WAAS on the first try, and the client performed a drift run to verify access to the lower part of the well.


The Well Miller, using the new star bit, successfully milled the flapper in one hour, and the Well Stroker set the WAAS in one run as planned.

Owing to the star bit’s innovative functionality, there was no flapper valve core to recover, which means that additional fishing runs were not necessary.

Capitalizing on prior experiences in similar wells, employing the new milling bit, and maintaining effective collaboration with the local e-line company, the entire operation was executed in seven days, saving the client time and money. Welltec’s small operational footprint also minimized HSE risks.

Finally, the client was satisfied with the teamwork between Welltec and the local e-line operator.