Schlumberger

Case Study: TrackMaster CH Saves USD 200,000 With First, Single-Trip Dual-Casing Exit Offshore India

Sidetracking BHA passed through full-gauge window and drilled ahead on first attempt

Challenge:

  • Mill a window in 13 3/8-in and 20-in casings in a single trip.
  • Provide a full-gauge window and rathole for the trouble-free reentry of subsequent sidetracking assembly.

    Solution: Provide the optimum window with TrackMaster CH cased hole whipstock system and a crushed carbide mill.

    Result: Successfully completed window and 2-m rathole in one trip, the first dual casing exit with a single trip in India, for a minimum savings of USD 200,000.

    Window required for sidetracking through dual casing string

    On an offshore well in India, the operator had planned to cut and pull the 9 5/8-in casing, sidetrack through the 13 3/8-in casing below the 20-in casing shoe, and drill ahead with a 12 1/4-in bit. However, only 293 m of casing could be retrieved, and with the 20-in casing shoe located deeper at 307 m, it was decided to sidetrack through the double, 13 3/8-in and 20-in, casing string. The alternative was to mill at least 50 m of 9 5/8-in casing and execute a single-casing exit below the 20-in casing shoe, an operation that would have taken a minimum of eight days, at a rig day rate of USD 50,000.

    Crushed carbide mill created exit in a single trip

    The TrackMaster CH whipstock was set at 279.8 m and a 12 1/4-in OD crushed carbide mill with three mills was used to mill the dual casing window in a single trip, the first time this operation was accomplished in India. The lead mill and follow mill came out 5/8 in and 3/8 in under gauge, respectively, while the dress mill was in gauge, demonstrating superior wear resistance. The formation was soft shale.

    Operator successfully sidetracked and drilled ahead

    7.14 m of casing was milled to create a full-gauge window, and 2 m of rathole was drilled during the trip. The entire operation was completed in four days, saving a minimum of USD 200,000. The sidetracking BHA entered the rathole and successfully drilled ahead on the first attempt. The TrackMaster CH whipstock system enables a longer casing window for trouble-free reentry of drilling assemblies.


    Download: TrackMaster CH Saves USD 200,000 With First, Single-Trip Dual-Casing Exit Offshore India (0.84 MB PDF)

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Sidetracking BHA Entered Rathole and Successfully Drilled Ahead on First Attempt

Trackmaster CH
The TrackMaster CH cased hole whipstock system enables a longer casing window for trouble-free reentry of drilling assemblies. 
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