Trajectory Design: Double Build vs. Horizontal

06 March 2013 Hello all,

I am in the process of designing well trajectories for a development in deepwater (~1300 m WD) Angola. Some of the targets provided by subsurface will require complex ERD, 3D, and near-horizontal directional designs, and I was hoping to get some advice / rules of thumb.

Here is my main question:

In general, would it be preferable to design a double-build well (i.e. kick of shallow to ~30 degrees and have a deep build (at around 4000 m TVD) to ~90 degrees (in order to align on the next target), or would it be better to remain vertical and build to 90 degrees deeper in the well (at the expense of a longer well)? Also, what if the sail angle for the double-build well is in the avalanching range (45-60 deg)?. My main concerns are hole cleaning and wellbore stability, however T&D could become an issue with the deeper directional work. There are no geological targets at the heel of the horizontal well case.

Any other high-level advice would be greatly appreciated. Note that we are still in the early stages of planning and rapid results are expected, so the 80/20 rule is in effect regarding the amount of work that goes into this.

Thanks.

Best regards,
Brian.

Assumptions:

• Rotary Steerable Systems will be used for all sections
• ”œShallow” kick off would be ~1000 m BML (16”/17” hole)
  

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