Post on 12-Mar-2018
Flyndre Field – Tilted oil water contact in a thin Palaeocene sandstone reservoir
Finn Engstrøm1, Thomas Dons Demsig2, Gerhard Templeton2 and Henk Wilms2
1Maersk Oil, Copenhagen, 2Maersk Oil, Aberdeen
Acknowledgement: Maersk Oil, Talisman Energy (UK) Limited, Eni UK, Noble Energy, Skeie Energy, Noreco, StatoilHydro and Petoro
Agenda
Introduction / Flyndre - Location and Geology
Drilling History / Pressure and Saturation Observations
Summary of Pressure and Saturation Observations
Potential Explanations for Observations
Causes for hydrodynamics
Conclusions
Flyndre Field Location
Flyndre Regional Setting 16 km
SSW NNE
Mid Miocene U/C
T. Oligocene
T. Eocene
T. Lwr. Eocene
Chalk L. Cret
U. Jur Zechstein Salt
Triassic
Rotliegend
ORION
Top Balmoral Sand Top Tor Chalk Palaeocene
30/18-2 Projected
30/18-3
FLYNDRE
30/14-2 30/14-1 N1/5-2
Low relief 4-way dip closures formed by compactional drape above deep
Mesozoic salt domes.
TD 15266
TD 14942
TD 9844
TD 12557
TD 13969
Paleogene Central North Sea Lithostratigraphic Scheme
• Lista Formation
− Deep water hemi-pelagics.
• Upper Balmoral Sandstone Unit
− Composite sharp based upward
fining sandstone unit 20ft to 30ft
thick
− Turbidites
− Total porosity ~22 pu
− Liquid permeability ~ 10 mD
• Lower Balmoral Sandstone Unit
− Dominantly debrites in this distal
area.
− Poor reservoir quality.
Permeability of Balmoral Sandstones
Kah vs Porosity & Shaliness
0.001
0.01
0.1
1
10
100
1000
10000
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Porosity ( )
Kah
(mD)
Clean1-5% Vshale5-10% Vshale10-15% Vshale15-20% Vshale20-25% Vshale25-30% Vshale30-35% Vshale35-40% Vshale40-50% Vshale50-60% Vshale60%+ VshaleVshale = 0%Vshale = 30%
Shale Line
Clean Sst Line
Flyndre / Oil Permeability / De-Saturation 2
0.01
0.1
1
10
100
1000
0.1 1 10 100 1000
Ka (mD)
Ko
(mD
)
Expectation
Equality Line
Ko = 0 assymptote
Ko(swi) after first mineral oilflood - 30/14-2Ko(swi) after 2nd Mineral OilFlush - 30/14-2Ko(Swi)- OWR 30/14a-1
Ko(Swir) - OWR 30/14a-1
Ko(Swi) Wettability 30/14a-1
Ko(swir) - extr. afterdesaturation - 30/14-2Ko(swi) before gas RP
Ko(Swir)extr. before GO RP
Non- Reservoir
Agenda
Introduction / Flyndre - Location and Geology
Drilling History / Pressure and Saturation Observations
Summary of Pressure and Saturation Observations
Potential Explanations for Observations
Conclusions
Causes for hydrodynamics
Well Location Map and Drilling History
Flyndre
30/14-3, 2007 ODT @ 9725’ Oil pressure
30/14-3z, 2007 ODT, Hrz well Oil pressure
N 1/5a-2, 1974 Non reservoir No Contact, no Pressure
30/13-7, 1997 Water bearing WUT @ 9740’ Water pressure
UK No
30/14-1, 1989 ODT @ 9617’ Oil Pressure
30/14-2, 2004 OWC @ 9594’ Oil pressure
Josephine
30/13-1, 1970 WUT @ 9484’
Depth structure map Near Top Balmoral Sand
2km
0 20000 40000 600009000 9500 10000 105000 0.2 0.4 0.6 0.8 1
9500
9600
97000 0.1 0.2 0.3 0.4 0.5
9500
9600
97000 0.2 0.4 0.6 0.8 1
AI (us*gm/ft*cc)
Well: 30/14-2 (Flyndre) Ft TVDss-Plot
Vshale ( ) Porosity ( ) Saturation ( ) Depths (ft tvdss)
Lista
Balmoral sst
OWCa
Base Balmoral
DT GR RES NEU DEN
30/14-2 Balmoral Sand & OWC
9682’ – 9700’
9758’ – 9698’
Present Day OWC
Base Balmoral Sand
PHO
TO
Base Debrite
Palaeo ODT, Oil Stain Occurs To The Base Of the Turbidite
Top Upper Balmoral Sst.
Top Lower Balmoral Sst.
OWC
25.4% 79.9mD
24.6% 44.4mD
24.9% 64.1mD
23.1% 38.2mD
26.7% 218mD
28.4% 266mD
27.1% 604mD
25.8% 328mD
25.5% 375mD
20.2% 24.5mD
23.8% 192mD
27.3% 302mD
25.5% 74.3mD
26.1% 154mD
27.8% 106mD
22.5% 106mD
24.7% NA
23.7% NA
23.8% 3.7mD
Balmoral sst
Base Balmoral sst
9400
9500
9600
9700
9800
99000 20000 40000 60000
9400
9500
9600
9700
9800
99000.00 0.25 0.50 0.75 1.00
9400
9500
9600
9700
9800
99000.00 0.10 0.20 0.30 0.40
9400
9500
9600
9700
9800
99000.00 0.25 0.50 0.75 1.00
AI (us*gm/ft*cc)
Balmoral Sst / Flyndre
Vshale ( ) Porosity ( ) Saturation ( )
30/14-1 N1/5a-2 30/13-7 30/14-2 30/14-3
N S Flyndre
9450
9500
9550
9600
9650
9700
9750
9800
9850
Dep
th ft
. TV
Dss
30/14-2
N1/5a-2
30/14-1
30/14-3Z
30/14-3
WUT 9740’
ODT 9566’
ODT 9725’
ODT 9617’
Non-net
OWC 9594’
30/13-7 Flyndre spill - 9730’ TVDss
Flyndre Hydrocarbon Contacts
Simplified MDT-data overview
• Limited Oil column
• No Water Points. Waterline based on the regional aquifer pressure map.
• Some data points are uncertain
• Pressure defined and sat-height model defined FWL’s in agreement (+/- 15 ft)
MDT-Pressures / 30/14-19500
9550
9600
9650
9700
9750
98006750 6770 6790 6810 6830 6850 6870 6890
Depth (ft tvd ss)
Pres
sure
s (p
sia)
U ni t s
F o rmat io ns
A l l P r es s ur es
O i l -‐ L i ne
W at er -‐ L ine
P r es s ur e F W L
Agenda
Introduction / Flyndre - Location and Geology
Drilling History / Pressure and Saturation Observations
Summary of Pressure and Saturation Observations
Potential Explanations for Pressure Observations
Conclusions
Causes for hydrodynamics
6844
6830
6850
Orion 6470-6613
Joyce 6809
6869
6853
6840
Recorded/Inferred Balmoral Aquifer Pressures @ 9700 ft tvd ss
Aquifer pressures decrease from NE -> SW
Water pressure Inferred Water pressure
2km
Agenda
Introduction / Flyndre - Location and Geology
Drilling History / Pressure and Saturation Observations
Summary of Pressure Observations
Potential Explanations for Pressure Observations
Conclusions
Causes for hydrodynamics
Compartmentalization?
For • May explain different OWCs Against • Cannot explain variations in
aquifer pressures • No seismic evidence of large scale
faulting • Can only with difficulty explain
the presence of remaining oil at the base of 30/14-2
Indifferent • No significant differences in PVT
or isotopes • No compartmentalization
identified along 30/14-3z
Through going fault creating two oil pools
30/14-2 OWC (9594 ftss)
Spill depth (9730 ftss)
2km
Perched Water?
For • May explain variations in
active OWC’s Against • Cannot explain the
presence of remaining oil below active OWC in 30/14-2
• Cannot explain observed variations in aquifer pressures
Oil
Free Water
Perched Water
Hydrodynamics ?
For • A SW-trending hydrodynamic
gradient can explain observed variations in active OWC
• A change (increase) in hydrodynamic gradient can explain the presence of remanining oil in 30/14-2
• Regional mapping of Balmoral aquifer pressures agree with the presence of active hydrodynamics
6844
6830
6850 Orion 6470-6613
Joyce 6809
6869
6853
6840
Datum Depth = 9700 ft tvd ss
2km
Agenda
Introduction / Flyndre - Location and Geology
Drilling History / Pressure and Saturation Observations
Summary of Pressure Observations
Potential Explanations for Pressure Observations
Conclusions
Causes for hydrodynamics
Balmoral Sand Regional Pressures
O/P < 50 psi
Andrew/Balmoral Sandstone limit
O/P < 50 psi
Greater Flyndre Field Area
O/P > 2000 psi Close to shale
pressures
• Highest overpressures in the Andrew/Balmoral sand units towards SE.
• Assumed driver for the flow of water in the Balmoral/Andrew sand units is expulsion of water from the shales (Swarbrick 2007)
• Inferred Balmoral aquifer pressures in the Greater Flyndre area agree with published map by Swarbrick.
From GeoPressure 2007 Report
Effect of Local Oil Pools in Balmoral
6830
6850
Flyndre Oil pool
10 psi/km
10 psi/km
5 psi/km
• 5-10 psi/km hydrodynamic gradients around Flyndre
• Oil pools may locally block for the flow of water in the aquifer and increase aquifer gradient
Change in aquifer gradient around Flyndre could suggest that the oil pools Limits the flow area
2km
Hydrodynamics in the Chalk
• Overpressure in the Chalk is often close to overpressure in the Paleocene sandstones
• Similar size and direction of the hydrodynamic gradient in Balmoral sst and the Chalk below.
From the Millennium atlas Are the observed hydrodynamics
in the Balmoral sst and the Chalk linked ?
General Model Hydrodynamics North Sea Basin
From Dennis 2003
Simple Model for Hydrodynamic Flow
Ekofisk, Tor and Hod Chalk
Balmoral sst
Overpressured Shales
Shales and Marls
Max Overpressure
1000-2000 bw/y
25-500 bw/y
30-150 bw/km/y
** Flow rates are for a 1 km wide model
30-150 bw/km/y
However, • Flow of water from the shales above a Balmoral oil pool
or from the chalk below will add to the complexity of the hydrodynamics conditions
Top Chalk Balmoral sst
FWL Due to regional hydrodynamics
Local change of FWL due to relative permeability effects
Hydrodynamic Concept Tested by Reservoir Simulation
hydrodynamic gradient
5700 m 9786 ft tvd ss
9596 ft tvd ss
Conclusions
• Observed variations in fluid contacts/pressures in Flyndre are more likely due to hydrodynamic effects than compartmentalization and/or perched water.
• A horizontal OWC in a thin permeable sandstone reservoir, embedded in shales, is rather an exception than the most likely.
Thank you for your attention - Any questions?
Disclaimer: The views in this presentation are those of the authors and do not necessesarily represent those of Maersk Oil or the Flyndre partners