licence relinquishment report ukcs p1668 ......licence relinquishment report ukcs p1668 blocks...
TRANSCRIPT
LICENCE RELINQUISHMENT REPORT
UKCS P1668
BLOCKS 43/26b & 43/27b
E.ON RUHRGAS UK NORTH SEA LTD
August 2011
CONTENTS
LIST OF FIGURES
1) SUMMARY
2) LICENCE INFORMATION
3) PROSPECTIVITY
4) RESOURCES SUMMARY
5) CLEARANCE
LIST OF FIGURES
Fig 1 Southern North Sea Asset Map
Fig 2 Johnston Field Asset Map
Fig 3 Representative Seismic Line Across Johnston Head & New Head
Fig 4 Johnston Top Reservoir Depth Map
SUMMARY
Licence P1668 comprises Block 43/26b and 43/27b (Fig 1, 2), was acquired in the 25th
Offshore Licensing Round awarded to a group comprising ERUK and Dana on 12 February
2009. The conditions of award were a drill or drop decision within 2 years and the JV
concluded that it was not attractive to drill a well within this timeframe and
relinquishment was effective 12 February 2011.
P1668 is adjacent to Johnston Field that has been in production since 1994 and was
developed via 5 wells as a subsea tie-back to the Ravenspurn North Field. Infill well
potential exists within the North Western part of Johnston - the “Head” area of the field.
The Johnston Field co-venturers identified a potential extension of Johnston Field – the
“New Head” on P1668. The main uncertainties surrounding the New Head were identified
as the connection / separation of the New Head from Johnston Field. The proposed work
programme to satisfy the award conditions comprised a dual lateral well drilled from the
existing Johnston Template that accessed both the New Head and the Head. Johnston
Head is depleted by production from the existing development wells and the New Head
was anticipated to be at or near virgin pressure – causing significant challenges to drilling
and completing the two legs.
The Johnston Field Reservoir is aeolian and fluvial sandstones inter fingering with sabkha
and playa lake siltstones and claystones. Top seal is the overlying Silverpit Claystone and
Zechstein evaporites.
The seismic interpretation of Johnston Field and P1668 is based on a reprocessed dataset
generated in 2006-07. The field data from five 3D surveys were time processed by CGG
and merged before pre-stack depth migration (PrSDM). Post-stack processing was
completed in April 2007. Data quality is good and the top Leman event can be picked with
reasonable confidence - even in areas of poorer imaging, such as below Plattendolomite
rafts.
Fig 1 Southern North Sea Asset Map
Fig 2 Johnston Field Asset Map
New Head
Head
De Keyser
Tail
LICENCE INFORMATION
Licence P1668
Blocks 43/26b & 43/27b
Conditions Drill one well to 3150m or 50m into the Carboniferous
whichever is shallower, or elect to relinquish the
licence within two years of award.
Round Awarded 25th
Date Awarded February 12, 2009
Date Relinquished February 12, 2011
Operator E.ON Ruhrgas UK North Sea Ltd (50%)
Co-Venturer Dana Petroleum (E&P) Ltd (50%)
PROSPECTIVITY
The seismic interpretation is based on an output area of 432sqkm reprocessed dataset
generated in 2006-07. The field data from five 3D surveys were time processed by CGG
and merged before PrSDM. The post-stack processing was completed in April 2007. Overall
data quality is good.
A Mesozoic graben orientated ENE - WSW lies above the Head of the Johnston Field that
materially affects local depth conversion.
PrSDM mapping showed a second tilted fault block north of Johnston field proper – the
New Head. There is no dip closure separating the New Head from the water bearing
43/26b-9 well – therefore if the New Head shares the Johnston field FWL, then a NNE
orientated De Keyser fault along the NW flank of the New Head would have to be sealing
(Fig 2). The risks on this scenario were the main reason for the Licence to be relinquished
before drilling.
Fig 3 Representative Seismic Line Across Johnston Head & New Head
Template
J1 J3, 3Y
Bunter Ss
Triassic
Corallian
Zechstein
RotliegendesLeman Ss
Plattendolomite
New HeadOld Head
PrSDM is 43m
too deep at J1
K LS2
NNE SSW
Fig 4 Johnston Top Reservoir Depth Map
The “Kumatage” lead also lies on P1668. This feature was drilled by the BHP operated
43/26b-10 well in 1998. This well penetrated 243ft of gas bearing Lower Leman
Sandstones. The well flowed at 53,000SCF/D on test and the P1668 JV considers the
Kumatage feature sub commercial.
RESOURCES SUMMARY
Johnston New Head (P1668) Probabilistic OGIP
Low 21BCF
Mid 42BCF
High 69BCF
CLEARANCE
E.ON Ruhrgas UK North Sea Ltd confirms that the Department of Energy and Climate
Change is free to publish the contents of this report.