PETRONAS Carigali and Schlumberger IPM have formed an alliance to develop a field in offshore Malaysia. Due to space limitations, a platform extension was installed to accommodate three additional conductor sharing wellheads (CSW). Project challenges include limited CSW pass-through, well collision risk, highly unconsolidated formations in the angle building section, directional control and shallow gas zones.

To avoid well-to-well collision caused by poor directional control, a pilot hole must be drilled under the conductor to provide good directional control in the unconsolidated sandstone. The pilot hole must also mitigate shallow gas risk. To achieve the reservoir hole size and accommodate dual gravel-pack completions, the pilot hole must be opened from 8–1/2" × 16" to allow subsequent hole section drilling.

The project team had to design a BHA that could efficiently deliver the objectives with minimal rig time. To solve the challenges a new hole opening methodology would be required. The pre-drill analysis included studies in: BHA durability/dynamic stability to ensure good hole quality; hydraulics and fluid dynamics to deliver proper cooling and hole cleaning; optimized combination of hole opening technologies. To reduce reaming runs/bit trips, a dynamic modeling system was employed to quantitatively analyze the interaction of various downhole tools and optimize the BHA configuration/drilling parameters.

The modeled dual eccentric PDC hole-opening BHA was run and successfully solved the challenges, mitigated risks and met the required drilling objectives for completing the six CSW wells. A post-drill simulation analysis was performed to analyze the dynamic downhole BHA behavior with the actual operating parameters.

The authors will explain how the BHA was developed and successfully used in the field to solve the unconsolidated formation challenge. Survey method and challenges of drilling through the conductor sharing wellhead are also discussed.

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