Fault-Induced
Bends on Schiehallion’s North Channel
De Miranda, Debora1 (1) BP
Exploration Operating Company Limited,
Schiehallion, a BP-operated 1.9 billion
barrel field 120km west of the Shetlands, produces from a series of stacked
Tertiary turbidite sands. The reservoirs are trapped by a 3-way combination dip
/ fault closure and a stratigraphic onlap / pinch-out to the east, set against
a pattern of East-West faulting.
3D seismic data are key to mapping the
reservoirs as the 25-30% porosity sands are low-impedance bright amplitude
anomalies when hydrocarbon bearing.
A confined channel, long recognised as
one of largest undeveloped hydrocarbon pools on Schiehallion, is now under
development.
This ‘
Seismic resolution is not high enough to
give confidence in tracing individual bodies. One main concern has been the
connectivity both between these internal channels and along the length of each
one. Image logs indicate slumping / reworking at the base of each of these
sands which appear to be extensive.
Multiple reservoir models were built to
test reserves against alternative visions of sand geometry and connectivity.
Selection of a development concept was
made recognising that channel boundaries and faults may seal but also that
elsewhere in the field this was not always the case. In reverse of the normal
arrangement, an up-dip injector and down-dip producer pair mitigate the risk of
cross fault flow and horizontal producers and injectors are drilled across the
constituent offset stacked channels that form the reservoir.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California