Schlumberger

Case Study: Cased Hole Whipstock System Performs Total’s First Multilateral Casing Exit Offshore Qatar

Whipstock system with tri-mill minimizes trips to mill full-gauge windows and provide ratholes for four horizontal sidetracks

Challenge: Mill full-gauge windows in 7-in casing and drill 5-m ratholes for four 6-in horizontal sidetracks.

Solution: Use 7-in TrackMaster CH cased hole whipstock system with
6-in tri-mill.

Result:

  • Milled window and drilled rathole for each sidetrack in one trip.
  • Drilled all four horizontal sidetracks to TD.
  • Retrieved whipstock in single trip after each sidetrack.
  • Mill full-gauge windows for multilaterals  

    Total Exploration & Production-Qatar, the operator of Al Khalij field approximately 130 km off Qatar’s eastern coast, wanted to drill four 6-in horizontal sidetracks from the ALK 114 well. Drilling the sidetracks required milling usable full-gauge windows through the well’s 7-in, 26-lbm/ft casing and drilling ratholes 5-m long, working from a jackup rig.  

    Drill sidetracks to TD  

    Total chose a 7-in TrackMaster CH whipstock system with a 6-in tri-mill to drill the ratholes for the four horizontal sidetracks. Milling time for the four 3.3-m windows ranged from 3 1/2 to 6 hours for a total of 19 hours. Drilling time for the four ratholes ranged from 1/2 to 1 1/2 hours for a total of 3 1/2 hours.  

    The BHA for the 6-in horizontal laterals passed easily through the full-gauge windows to drill the sidetracks to TD. After each sidetrack was completed and the drillstring pulled out of the hole, a retrieving assembly was run to remove the TrackMaster CH whipstock system.  

    Mill and drill in one trip  

    All four horizontal sidetracks were drilled to TD. Each of the four exits required just one trip to mill a window in the 7-in casing and drill the rathole and one trip to retrieve the whipstock after the 6-in horizontal lateral had been drilled to TD.


    Download: Cased Hole Whipstock System Performs Total’s First Multilateral Casing Exit Offshore Qatar (0.62 MB PDF)

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TrackMaster CH Cased Hole Whipstock System

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The TrackMaster CH cased hole whipstock system delivers quality, full-gauge windows for exiting steel casing.
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