Schlumberger

Case Study: TrackMaster TT Mills Tubing Exit Offshore Norway Protecting Original Wellbore’s Production Capability

Whipstock system enables deployment of directional drilling assembly capable of a 45°/100-ft build rate

Challenge: Mill a window through 5-in, 15-lbm/ft liner and drill a rathole for deployment of a thru-tubing directional drilling assembly capable of a 45°/100-ft build rate. And upon completion of the lateral, resume production from the original wellbore.

Solution: Run 4-in OD TrackMaster TT thru-tubing whipstock system and 4.2-in OD FasTrack one-trip mill, leaving the whipstock downhole to facilitate reentry into the lateral.

Result: Created window and rathole in 4 1/2 h, dressed the window, and drilled ahead using a directional BHA with a positive displacement motor (PDM), which set a 3.8° bend angle.

Sidetrack through tubing with ability to resume production from original wellbore

To sidetrack through tubing from a 21.7° deviated well in the North Sea, an operator required a window in 5-in, 15-lbm/ft, 13% chromium liner, through which a directional assembly capable of a 45°/100-ft build rate could be deployed. The whipstock had to be left in place to facilitate future reentry of the lateral and production from the original bore had to be maintained once the lateral was drilled.

Run TrackMaster TT whipstock system designed for the purpose

TrackMaster TT thru-tubing whipstock system is designed to pass through the tubing ID; once below the tubing string, it can be hydraulically anchored inside the liner to enable window milling operations. Its unique geometry compensates for the relative size difference between the whipstock and casing diameters. Fluids can flow past the whipstock, which is left downhole, allowing production to be maintained from the original borehole as well as the lateral. The back of the whipstock was fluted to provide additional flow area. A 4.2-in OD FasTrack one-trip mill was used to create the window at 3,024 m; PDC inserts were used over 30% of the cutting structure.

Deploy directional assembly suited for high-build-rate successfully

  • A 1.7-m window was milled in 3 1/2 h and a 1.9-m rathole was drilled in 1 h, in a single trip.
  • A subsequent run was made to dress the window, ensuring a full-gauge, useable exit for trouble-free reentry of drilling assemblies and minimization of bending stresses.
  • The directional drilling assembly, including a 3.8° PDM and a 4 1/8-in bit, was successfully deployed through the casing window.

Download: TrackMaster TT Mills Tubing Exit Offshore Norway Protecting Original Wellbore’s Production Capability (0.63 MB PDF)

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