This paper describes the new methodologies, complex engineering work, and fit-for-purpose processes that were adapted in the design, fabrication, load-out, and installation of the heaviest and largest stacked template structure (STS) installed by a jack-up rig to date.

Lifua is one of the marginal fields within the Block 0 concession in offshore Angola. The development plan for these marginal fields requires short-cycle and cost-effective designs to be economically feasible. Utilizing a minimum functional objective approach, Lifua-A was planned as a proof-of-concept for this strategy which involves a repeatable solution developing a standard wellhead platform design, standard well designs and a factory-repeatable platform fabrication, installation and well execution process.

The STS design was the selected solution for the development of the Lifua field. This rig-installable platform design was first developed and installed in offshore Indonesia in 1995 with slots for three wells and rated for 150 ft of water depth. Lifua-A STS is a ten-well platform with a planned installation at a water depth of 205 ft. As a result, a new enhanced STS design and installation procedure was required. As the structural design work and fabrication progressed, the technical requirements for the jack-up rig were also developed. Upon contracting the rig, detailed engineering work was undertaken to modify the rig's cantilever system to meet the lifting and installation requirements of the STS modules. The upgrade increased the rig's cantilever longitudinal skidding capability to 85 ft with a lifting capacity of 400MT. In addition, engineering work was carried out to size and install a hydraulic hammer on the rig floor to drive the 42-in. and 36-in. conductors. Finally, the laying of the subsea flexible production flowline, thermoplastic composite water injection pipeline, and subsea power cable were all engineered in a way where they could be pulled in and up the STS platform from the rig floor utilizing a drillpipe-sling assembly and a winch cable.

The installation of the Lifua-A STS was executed according to plan, achieving the short-cycle objective by delivering the project within three years from FID to first oil. In addition, the project planning and execution was successfully carried out during the COVID pandemic. One key success factor was having the cross-functional groups working together as one team, from the development of the design to fabricating the structures and actual offshore installation. Lifua-A unlocked the marginal reserves of the Lifua field by stretching the limit of the application of the STS. This success opens the possibility of utilizing the same solution to other similar marginal fields.

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