Pierce Field Development by FPSO Solution

Abstract

Abstract The Pierce field, which is located in the UK sector of the North Sea, has been developed using a Multi-Purpose Shuttle Tanker (MST) converted into a field specific Floating Production and Storage Offshore (FPSO) facility. First oil from the development was achieved in early 1999. This paper describes the overall field development from reservoir through to export solution. Pierce is an oil field associated with twin salt diapirs with ultimate recoverable reserves of 110 million barrels of oil and 182 billion cubic feet (bcf) of gas located in Palaeocene sands in the North Sea Central Graben. The field has been developed using horizontal drilling technology with complex directional trajectories and long reservoir sections up to 6,500 ft in length. These well lengths were necessary to optimize recovery from the steeply dipping beds of the reservoir formation. Six oil producers and two gas injectors have been drilled from two sub sea templates located 2.2 km from the FPSO. The "Berge Hugin" FPSO is of the MST design equipped with modular topside facilities. The subsea concept has enabled the use of a small innovative turret system totally enclosed within the hull of the FPSO. Introduction Field History. The Pierce field lies within licence blocks 23/22a and 23/27 in the Central North Sea, 280 km east of Aberdeen in 272 feet of water. Enterprise Oil is responsible for operating the field on behalf of the Pierce owners: Enterprise Oil, Ranger Oil, MOC, Agip and Petrobras. The Pierce South accumulation, previously known as Pierce, was discovered in 1975 by Ranger Oil with well 23/27-3. The discovery well encountered oil in Palaeocene sandstones and Palaeocene/Cretaceous chalks on the western flank of the Pierce South diapir. The well tested oil and gas at 3000 bopd and 2.1 mmscfgpd from the Palaeocene Forties Sandstone Member. Several appraisal wells were drilled on Pierce South following discovery. Three wells were drilled from 1978-83, but all penetrated the Forties sandstones below the oilwater contact. The first appraisal well to encounter hydrocarbons was 23/27-8, drilled in 1991. The well encountered Palaeocene sandstones and Palaeocene / Cretaceous chalks on the western flank of Pierce South. The well had a maximum test rate of 5700 bopd and 5.1 mmscfgpd from Forties sandstones. The remaining Pierce South appraisal wells are 23/27-9, - 10, and -10z. Well 23/27-9 was completed in 1992, having penetrated Palaeocene sandstones and Palaeocene / Cretaceous chalks on the northern flank of Pierce South. The 23/27-10 well was drilled on the southern flank of Pierce South in 1996, and again penetrated Palaeocene sandstones. Pierce North, formerly known as Medan, was discovered by BP well 23/22a-2 in early 1990. The well encountered wet gas in a thin section of Palaeocene sandstones and Palaeocene/Cretaceous chalks on the western flank of Pierce North. An appraisal well, 23/22a-3, was drilled in 1991 on the eastern flank of the Pierce North diapir.