The eni Petroleum Nikaitchuq field is located offshore in the Beaufort Sea within the North Slope region of Northern Alaska. The 12-1/4" intermediate section of the Nikaitchuq wells are drilled with a Rotary Steerable System (RSS) at high inclination prior to landing near-horizontal in the reservoir. The intermediate hole section passes through a very abrasive sand with an unconfined compressive strength (UCS) of approximately 22 ksi called the Lower Ugnu.
Historically, the drilling of the 12-1/4" intermediate section has been drilled with two to three bit runs consisting of various polycrystalline diamond compact (PDC) and tri-cone designs. This was due to the abrasive nature of the Lower Ugnu combined with interbedded soft sand causing ledging, high stick-slip and lateral vibrations which lead to consequential bit/BHA damage and a reduction in drilling efficiency.
With the objectives of drilling the section in one run and to minimize damages to the RSS and MWD, a vibration mitigation workshop was conducted between the Nikaitchuq drilling team and key service company experts. The workshop team focused on four strategies to mitigate vibrational issues:
Bottom Hole Assembly modification.
Introducing new technologies and tools into the drill string to capture high density data and mitigate vibration.
Mapping and prediction of the hard streaks within the intermediate section.
Modification of drilling practices where possible.
BHA and bit vibration modeling, new vibration mitigation tools, Measurement While Drilling (MWD) and multi-axis downhole vibration measurement data, BHA and stabilizer reconfiguration, as well as implementing various drilling parameters were all investigated and applied in both the front end and at the rig site.
This paper demonstrates the systematic approach the Nikaitchuq drilling team implemented to mitigate damage to the bit and downhole tools as well as improve drilling performance by minimizing stick-slip and lateral vibrations.