The West Franklin HP/HT Field discovered in 2003 by the well 29/5b-F7z was drilled on a simple structure defined using the 1996 Elgin/Franklin 3D seismic -vintage data which has since been superseded by state-of-the-art seismic processing techniques. The original PSTM displayed relatively continuous seismic reflectivity with large uncertainty on imaging and interpretation.The highly productive porous sandstone interval within the Upper Jurassic Fulmar Formation was identified as a high amplitude reflector due to a strong decrease in impedance. Anisotropic PSDM processing followed by an acoustic inversion study highlighted the probable extension of this 'Porous Zone' to the west and underlined the high potential for a second appraisal/development well.Positive results from the second well 29/5b-F9y in 2007 showed dramatic thickening and improvement in reservoir quality to the west and initiated additional PSDM processing of the original 1996 data. Following developments in tomography and migration algorithms, strong imaging improvements were observed from the integrated anisotropic velocity model updates and by reducing the amount of destructive interference from multiples. The resulting interpretation allowed for a better understanding of the salt tectonics and in predicting Fulmar reservoir thickness to the west.A 7km Long Offset 3D survey acquired by CGGV in 2009 with subsequent PSDM processing is bringing further imaging improvements over areas of amplitude degradation leading to potential upsides. A first 4D monitor acquisition over Elgin/Franklin in 2005 (before production had started on West Franklin in 2007) is being followed-up by a second 4D monitor in 2011, aimed at providing additional information on the depletion pattern around the field. Such strategy in ongoing investment in seismic data will further unlock the resource potential over and around West Franklin in the coming years, ensuring a mature area remains in the spotlight.

West Franklin is an HPHT field in the Central Graben Area of the UK ContinentalShelf discovered in 2003. The field went into production in 2007 via a welldrilled from the Franklin Well Head Platform (WHP) of the existingElgin/Franklin facilities. Results from a second well generated the case for asecond phase of field development. Development studies at the preliminary stage of the second phase eliminated theoption of further field development by drilling from the existinginfrastructure. Subsea development was also screened out due to technology gapsin subsea HPHT applications. A new WHP tied back to the existing Elgin/Franklinfacilities became the prime development candidate in the conceptual stage. However, time was of the essence as the two existing wells were still producingand depleting the reservoir, introducing uncertainty to the drillingfeasibility due to the phenomenon described as the "infill challenge". In orderto mitigate these drilling risks the development strategy was to pre-drill thewells. Drilling commenced from a subsea template and continued until a jacketwas designed, fabricated and installed in September 2012. The acceleration ofthe jacket installation minimized the number of wells to be reconnected from adeep set tie back and allowed the other wells to be completed from a wellaccess deck. The WHP topsides will be installed later in 2013. In addition to managing multiple interfaces the project faced significanttechnical challenges generated by ultra HPHT reservoir conditions. Overcomingthese in time to optimize the design was difficult in itself i.e. topsideslayout/orientation and associated jacket appurtenances; design of the OverPressure Protection System and risers and their installation within the jacket. The list goes on and includes timely co-venturer and UK regulatoryapprovals. This paper addresses the key challenges and decisions taken along a stageddesign and approval process for a development in an ultra HPHT environment. Introduction The Elgin/Franklin field is located in the Central Graben Area of the NorthSea approximately 240km east of Aberdeen in 92m water depth (Figure 1). Thereservoirs (shore face sandstone of Late Jurassic age) are 5,500m deep andpresent ultra high pressures (1,100bar) and temperatures (200degC).