Overcoming Field Development Challenges in Depleting Ultra HPHT West Franklin Field

Abstract

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).