Exploration and appraisal of the South Arne Field, Danish North Sea

Abstract

The South Arne Field lies in the Danish sector of the North Sea Basin 250 km WNW of Esbjerg on the Danish mainland. It is a chalk field 12 km by 3 km. The field was initially discovered in 1969 by the I-1 well which found a thin Maastrichtian Tor Formation producing up to 4040 BOPD upon test. The second well on the field (Baron-2) was drilled over 20 years later on the southwestern flank. The aim of this well, in addition to targeting deeper Jurassic prospectivity, was to test the concept that the chalk reservoir thickened off-structure. This well encountered no productive chalk reservoir and the prognosed Jurassic reservoir was not reached. Following a change of operator in 1994, the Rigs-1 well was drilled in the northern part of the field where the interpreted structure was most complex. The well was located on 2D seismic data towards the middle of what was interpreted to be a gas cloud. This well encountered a much thicker chalk reservoir sequence than had previously been drilled on the field. Following the acquisition of 3D seismic data and an intensive, integrated geological and geophysical work programme, an appraisal well (Rigs-2) and a down-dip sidetrack were planned in an area outside the gas cloud where the reservoir was predicted to be of high quality. These appraisal wells were very successful in their objectives and proved a stratigraphic element to the hydrocarbon trapping mechanism. The field development plan envisages the extensive use of horizontal wells and first oil is currently scheduled for mid 1999. Reserves are presently estimated to be 89 × 106BBL oil, and 200 × 109SCF of associated gas.