Case Study: Deepwater Casing Window and 85-ft Rathole Completed in One Trip for 9,551 ft of Tight-Tolerance Liner

TrackMaster CH whipstock system provided an exit with DLS less than half the expected value


  • Mill a window in 13 5/8-in, 88.2-lbm/ft casing in one trip, and drill the 85-ft rathole required to accommodate the rotary steerable system.
  • Provide a long, full-gauge window for the trouble-free reentry of subsequent drilling assemblies.
  • Create an optimum window profile to minimize bending stresses in the 9,551 ft of 11 3/4-in FJ liner to be deployed through the window.

Solution: Provide the optimum window with TrackMaster CH cased hole whipstock system, designed to deliver results in tight tolerance applications, and FasTrack one-trip trimill.

Result: Successfully completed window and rathole in 14 1/2 h and one trip, with a dogleg severity (DLS) less than half forecast value.

Tight tolerance liner challenges successful sidetrack in deep water

An operator in the Gulf of Mexico required a window in 13 5/8-in casing, to deploy 9,551 ft of 11 3/4-in FJ liner on a Walker Ridge deepwater reentry project. With a casing pass-through ID of 12.375 in and maximum liner OD of 11.9 in, a very tight tolerance had to be accommodated.

TrackMaster CH system creates window in a single trip

A 12 1/4-in OD FasTrack one-trip trimill was used to mill the window in a single trip. The TrackMaster CH whipstock system enabled a longer casing window for trouble-free reentry of drilling assemblies and minimization of bending stresses in the liner and connections.

Operator drills ahead and lands 9,551 ft of liner

  • The casing window and 85-ft rathole were completed in 14 1/2 h and one trip.
  • Six trips were made through the window during drilling operations with only 4,000 lbf of increased drag at the window.
  • At 4°/100 ft, the apparent DLS achieved over the whipstock interval was significantly better than the calculated 8.67°/100 ft.
  • Results were verified with a six-arm caliper prior to running the liner.
  • 9,551 ft of 11 3/4-in FJ liner was successfully landed and cemented without incident.

Download: Deepwater Casing Window and 85-ft Rathole Completed in One Trip for 9,551 ft of Tight-Tolerance Liner (0.61 MB PDF)

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