New Innovative Approach to the Upgrade of Ageing Existing Offshore WellHead Platforms

This paper details a slip-over design concept and challenges for the replacement of existing ageing offshore Well-Head (WH) fixed platforms for relatively shallow and deep-water fields applications. A cost-effective slip-over design concept for replacement of existing platforms and the utilization of existing wells with cost effective reduction and increased oil production has been developed. The design has been implemented repeatedly in relatively shallow water offshore fields that requires minimum offshore execution work schedule with minimum installation risk, optimized shutdown duration and minimum loss of oil production. Further enhancement of the design ensured any future plan for installation of a slipover platform in a relatively deeper water would overcome the requirement for a much bigger derrick vessel hook-height capacity mobilization. The new developed slipover structure design, which is based on Company's standardized, simplified and SIMOPS (simultaneous operations capable) (SSS) multi-bay four (4) legged jacket, is compliant with all the latest Company and applicable international standards, which involves the demolishing of existing structure together with the leg-through piles to a depth of between 1.5-2.0m below seabed and transported to reclamation site, while existing well conductors remain and are secured in place. A new slipover platform is installed over existing conductors with additional well slots design utilizing the same existing platform seabed location for increased production. A minimum shutdown requirement for installation, additional production potential and reduced CAPEX and OPEX are achieved. This design concept is also extended to a relatively deep-water fields application by either, the mobilization of a higher installation derrick vessel hook-height lift elevation for utilization over existing free-standing wells or the use of a two-piece stacked jacket design.