Schlumberger

Case Study: TrackMaster CH System Performs First Deepwater Low-Side Casing Exit in Mexico

Whipstock system mills 10 5⁄8-in, low-side casing exit, saving USD 655,000

Challenge: Perform a deepwater, low-side exit in 11 3/4-in casing in one trip and drill a rathole to allow continued drilling of a 10 5⁄8-in well section.

Solution: Run the TrackMaster CH cased hole whipstock system to sidetrack on the low side of the hole.

Result: Milled an 11 3/4-in casing exit in deep water with low-side toolface orientation of 154°, and drilled a 16.4-ft rathole to allow continued drilling of a 10 5⁄8-in well section in one trip, saving USD 655,000.

Deepwater sidetrack presents challenge

In the course of drilling the 10 5⁄8-in section in deepwater Gulf of Mexico off the Mexican coast, borehole instability led to a fish being left in the borehole. PEMEX determined that undertaking a sidetracking operation was the best course of action. Schlumberger suggested using the TrackMaster CH cased hole whipstock system. The whipstock system’s running assembly consists of a mill and whipstock assembly with an expandable hydraulic anchor. The mill has an aggressive cutting structure that combines cylindrical tungsten carbide cutters, PDC cutters, and crushed tungsten carbide.

First-time low-side casing exit for a unique application

The casing exit was planned on the low side to optimize the directional plan and to prevent tracking into the old borehole outside of the casing. Although more difficult to set the whipstock to the low side, this approach would reduce the directional work needed to hit PEMEX’s drilling target. With a slight modification to its hinge area, the TrackMaster CH system allows an upward force to be exerted at the tip of the whip face when setting the permanent packer and expandable anchor, thereby overcoming the natural gravitational forces of a low-side casing exit. This upward force is not produced until the packer is energized, or the anchor is set.

After modifying the TrackMaster CH system, the low-side sidetracking operation was conducted in seven steps:

  • Run the whipstock and milling assembly
  • Orient the whipstock assembly with MWD to 154°
  • Hydraulically set the expandable anchor
  • Release the mill from the whip
  • Mill the window
  • Drill the rathole
  • Pull out of hole

First deepwater, low-side casing exit delivers savings for PEMEX

The TrackMaster system milled an 11 3/4-in casing exit in deep water with low-side toolface orientation of 154° and drilled a rathole in one trip to allow continued drilling of a 10 5⁄8-in well section. As a result of this inventive effort, wellbore inclination was reduced due to low-side orientation, offering a complete solution for the directional trajectory and saving USD 655,000.


Download: TrackMaster CH System Performs First Deepwater Low-Side Casing Exit in Mexico (0.51 MB PDF)

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