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Conductor Anchor Node Optimizes Efficiency of Riserless Deepwater Exploration Drilling

This summary is based on the paper "Conductor Anchor Node Optimizes Efficiency of Riserless Deepwater Exploration Drilling," presented by E. Kopperud, A. Knudsen, S.J. Dybvik, F. Hardinges (Det norske oljeselskap ASA), and W. Mathis (NeoDrill AS), published in the Journal of Petroleum Technology in 2017. The full paper can be accessed through the Society of Petroleum Engineers at Journal of Petroleum Technology.


Essential Highlights

  • Technology Overview: The Conductor Anchor Node (CAN) technology was introduced for deepwater drilling to optimize riserless operations. It acts like a suction anchor to stabilize the well's conductor on the seabed.

  • Operational Efficiency: The CAN technology reduces rig time and costs by allowing preparatory work to be completed before the drilling rig arrives. This streamlines operations and accelerates well startup.

  • Case Study - Ivory Well: In the Ivory exploration well in the Norwegian Sea, the CAN system shortened the conductor length needed, saving significant rig time. It allowed for quicker jetting of the conductor and minimized weather-related delays.

  • Results: Using CAN technology led to a significant time savings of 7.3 days compared to traditional methods during the riserless drilling phase, enhancing the overall efficiency of the drilling operation.


Introduction

The Conductor Anchor Node (CAN) technology, developed by NeoDrill, was introduced for Centrica’s Ivory deepwater well in the Norwegian Sea to optimize riserless operations. The CAN, a large steel cylinder, acts like a suction anchor by setting into the seabed to secure the conductor (top-hole casing). It was installed using a dynamically positioned (DP) vessel ahead of the rig’s arrival, saving rig time and simplifying logistics.


Pre-installation steps, such as placing marker buoys and transponders, were completed in June 2014, enabling efficient startup when drilling began in October. A pilot hole was drilled 50 meters from the CAN to assess soil strength and ensure safe operations. All riserless activities were optimized using dual derricks to reduce rig time and maximize efficiency.


Well Design and challenges

The well's strategy was to complete pre-rig work to minimize weather risks and optimize operations. NeoDrill preinstalled the CAN, reducing the conductor length to 50 meters compared to the conventional 80-100 meters. Conductor jetting, the quickest method, was used without requiring cementing or tripping. The CADA tool enabled continuous drilling, and the CAN ensured safe conductor landing without waiting for soil consolidation. A pilot hole was drilled 50 meters from the CAN to confirm jetting feasibility.


Ivory operational summary

The pilot hole was drilled by an auxiliary rig, as the main rig needed to remain available for landing the BOP and riser. The conductor was positioned in the moonpool to keep the main rig free. The BOP and riser were prepped offline while the auxiliary rig jetted the conductor and drilled ahead for the next section. The BOP was landed just before surface casing was cemented. The CAN installation took 4 to 5 days, with the full penetration achieved in 4 hours, and a final inclination of 0.42°. Preinstalled transponders and buoys saved rig time.


Pilot hole

A pilot hole was drilled 50 meters southwest of the main location to assess the feasibility of conductor jetting. Data collection was challenging due to rig heave, but a weight on bit (WOB) of 5 tons between 1495 m and 1505 m indicated a stronger formation. A significant change in formation strength was observed at 1501 m. Logging confirmed a clay sequence at the bottom, allowing the conductor jetting operation to proceed. The pilot hole was drilled to a vertical depth of 2200 m.


Conductor jetting

The jetting operation involved a 49.8-meter conductor run with a NeoDrill hanger to land into the CAN. The CADA tool was used to drill ahead, and the conductor was kept moving every 2-3 meters to prevent sticking. After landing the casing, the CAN's axial load capacity allowed immediate drilling without a soaking period. This approach saved 7.3 rig days compared to the expected plan, demonstrating the efficiency of using the CAN with a short jetted conductor in dual-derrick operations.



Fig 2: The conductor housing with the CADA tool landed inside the CAN.


Conclusion

The CAN technology, deployed in the Ivory deepwater exploration well, optimized well construction operations by reducing the time and cost of riserless sections. By preinstalling the CAN, jetting operations became more efficient, allowing for shorter conductor lengths compared to traditional methods, and minimizing risks associated with soil consolidation and conductor movement. The CAN's axial load capacity supported operations without requiring extended cementing processes. The overall results demonstrated significant time savings, with 7.3 rig days spared compared to expectations. This method not only increased operational efficiency but also reduced environmental impact and enhanced safety, making it a key solution for riserless drilling in deepwater conditions​


For more detailed insights, the full paper can be accessed through the Journal of Petroleum Technology.


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