New Well Foundation Concept, As Used at a Norwegian Sea Well

Abstract

A new and safer, high load capacity well construction concept has been developed. This new well foundation system as installed at a Norwegian Sea well location by Det norske oljeselskap ASA, is described herein, as well as its use and recovery. Heavy Blow Out Preventers (BOP) are normally used on drilling rigs designed for deep water and arctic applications, and heavier BOPs will have a negative impact on the stability of the well head. To mitigate these negative impacts, a new suction anchor type well foundation concept; CAN (Conductor Anchor Node) has been developed. The CAN unit provides sufficient load capacity for safely carrying heavy BOPs as well as X-Mas trees, thus protecting the well from fatigue capacity "consumption" in the drilling phase. The use of the concept will also reduce cuttings and cement disposal to the sea, which may be further important aspects in arctic and sensitive marine environment areas. The CAN will also mitigate the risks of the well becoming over-loaded by undesired, accidental loads, e.g.: as a result of a rig drive off/drift off situation. This is achieved by mobilising substantial carrying capacity from the soil through the CAN's large cross sectional area and captured soil mass. This is an important aspect in view of risk mitigation and improving possibilities of applying contingency means in case of undesired events or disasters, such as the Macondo case. The concept offers significant advantages in reducing rig time; as it enables pre-rig conductor installation, thus reducing top-hole construction costs and rig failure risk exposure. The concept's viability and advantages have been demonstrated by a number of full scale applications ranging from 270 m to 1 150m water depth on the Norwegian Continental Shelf. The CAN will be a facilitator for safe jetting of conductors (only short length conductor needed), as well as being an enabler for achieving successful cement jobs (if installed by drilling and cementing), as the conductor remains supported and motionless during cement set-up.