This case study presents the first deployment of a Conductor Anchor Node (CAN®) well foundation with a surface wellhead on the high-pressure, high-temperature (HPHT) Isabella Appraisal well, located in interbedded seabed conditions in the UK Central North Sea. Previous use of similar well foundations has been limited to subsea wells drilled with floating rigs. In this "world-first" application, the system was used with a heavy-duty jack-up (HDJU).

A well foundation is a steel cylinder which is installed on the seabed in a similar manner to a suction anchor. The unit contains an open guide pipe that can be drilled through, with a landing shoulder to support the well’s conductor pipe. To date, installations of well foundations have always been performed by a dedicated vessel prior to the rig’s arrival. In this case, the foundation was installed after the HDJU was positioned on location, using the drawworks to conduct the installation offline, during pre-spud preparations. This reduced cost and removed the risk of clashes or disturbance during the positioning of the HDJU.

The well foundation was mobilised by supply vessel and lowered to seabed by the drillstring. A remotely operated vehicle (ROV) was used to apply suction to install the unit. The inclination of the well foundation was manipulated by adjusting drillstring tension and skidding the drilling package to apply horizontal loading. The unit was successfully installed with the observed inclination and penetration within the target range. Next, the 36 in. tophole was drilled through the foundation guide pipe, and the 30 in. conductor was run and cemented back to the foundation top. A cuttings and cement removal system was used to prevent accumulation of solids that could hinder the recovery operation.

The main motivations for operator TotalEnergies in using the well foundation technology were: ensuring adequate structural support for the well in challenging shallow formations; reducing wellhead movement and hence improving fatigue life; and achieving a competent cement sheath due to reduced conductor movement. This paper will provide details on the well delivery drivers of using this technology to mitigate technical risks on this challenging appraisal well.

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