10.11440060477_si_001.pdf (18.14 MB)
Upper Brent reservoir variations, Otter Field, Northern North Sea
journal contribution
posted on 2020-04-30, 14:18 authored by S. D. HARKER, C. LONGIS, J.-F. ROUX, L. LIVINGSTONE, H. THOMAS, K. MILNE, G. HOLM, S. STROMBERGOtter is the most north-westerly of the Brent Province fields of the Northern
North Sea, located in UK blocks 210/15a and 210/20d, 530 km north of
Aberdeen, operated by TOTAL with partners Shell U.K. Exploration and
Production, ExxonMobil and Dana. The field was discovered by the Phillips
210/15-2 well in 1977 (then called Wendy) and appraised by Fina well 210/15a-
5 in 1997, following 3D seismic acquisition in 1994. Decision to proceed with
development was confirmed after the success of appraisal well 210/15a-6
drilled by TotalFina in 2000. The Otter structure is an easterly dipping tilted panel that is divided into four
major blocks and several minor blocks by a network of subsidiary faults. The
reservoir is the Middle Jurassic Brent Group, with the uppermost Tarbert
Formation shallow marine sandstones comprising the main producing target.
The oil source rock is the Late Jurassic Kimmeridge Clay, present in the offstructure
areas, though locally absent over the Otter field area, top seal being
provided by the Mid to Late Jurassic Heather shales. The Otter oil is a medium
gravity crude (36.5° API) with a GOR of 79m3/m3 (443 scf/bbl), in a normally
pressured reservoir at a crestal depth of 1970m subsea. The core displays from the 210/15a-5 and 210/15-2 wells, illustrate the major
reservoir target of the Tarbert, the upper contact with the Heather Formation
caprock and the facies variations in the underlying channelised Ness
formation. The 2002 to 2003 Otter field development drilling campaign utilised a
combination of detailed trajectory planning and integrated geosteering
techniques, including real time transmission of borehole image data and
wellsite chemostratigraphy. The objective of this work was to maximise oil
recovery, with a minimum number of wells, from the complexly faulted Otter
structure. To achieve this, sub-horizontal production wells were planned to
track near top reservoir, through the structural culminations, to connect
adjacent fault blocks. Illustrations of this work are presented in the
accompanying poster displays.
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TOTALOtter structureHeather Formation caprockUpper Brent reservoir variationsoil source rockNorthern North SeaAPIsub-horizontal production wellsMiddle Jurassic Brent GroupBrent Province fieldsUKJurassic Kimmeridge Clayborehole image datachannelised Ness formationJurassic Heather shalesmaximise oil recoveryNorthern North Sea OtterOtter field area1970 m subseapartners Shell U.K2003 Otter field development drilling campaign utilisedGORGeology