Seismic Characterisation of Shallow Gas in The … - Underexplored plays... · Seismic...
Transcript of Seismic Characterisation of Shallow Gas in The … - Underexplored plays... · Seismic...
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Seismic Characterisation of
Shallow Gas in The Netherlands
Underexplored Plays Regional Conference, Stavanger 2015
Mijke van den Boogaard & Guido Hoetz (EBN)
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Hazard?Deep source?
Opportunity?
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Shallow Gas Pays Off!
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www.offshore-mag.com
2007
Today ~8 bcm gas produced www.dana-petroleum.com
2009
www.hsm.nl
2011
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Outline
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1. Introduction
2. New play rather than hazard
3. Seismic characterisation
4. Summary
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Denmark
Geological Setting
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300 –800 m
Bright Spots
Base Tertiary
Base Chalk
Shallow Gas (SG) = gas in unconsolidated, Miocene-Pleistocene sands
MMU
Modified from kennislink.nl
UK
NO
NL
SW
Google Maps
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~1
km
~10 km
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amplitude anomalies
salt domes
Mid-Miocene
Unconformity
Top Chalk
SW NE
Geological Setting
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Shallow Gas in Norway
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Shallow Gas in Norway
Eriksen et al., 2011 & NPD website
• 2005 Gas discovery• Clean unconsolidated sands• Pleistocene glaciofluvial / marine • Nordland Gp sediments• Top @ 574m
• 18.7 m gas column• 99.5% methane• Φ = 0.33• N/G = 0.99• SG = 0.88
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Shallow Gas Portfolio
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Producing
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Shallow Gas Production
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• Presence shallow gas known since 70’s
• Early water breakthrough & sand production expected
→ fields not developed
• Currently 3 successfully producing fields:
- A12-FA (2007)
- F02a-B-Pliocene (2009)
- B13-FA (2011)
• Technical breakthrough
(e.g. sand control in horizontal wells)
Chevron, Oil&Gas Journal, 2009
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Shallow Gas: new play rather than drilling hazard
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1. New technology proven successful for SG developments
2. New 3D seismic points to more opportunities
3. Small field tax incentive applicable
Shallow fieldsShallow leads3D seismic
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Seismic Characterisation Shallow Gas
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SG portfolio
Bright Spots identified (RMS ampl. scanning)
150 leads
Bright Spot ranking
Geometrical Characterisation
Seismic Characterisation
Highest ranking Bright Spots:
3D reservoir model Volumes
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Seismic Characterisation Shallow Gas
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VolumesDHI’s
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Seismic Characterisation - Amplitude
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A12-03 B13-04
TWT
(ms)
NW SE
A12 field (producing)
GR GR
Sg = 70%
Sg = 0%
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Seismic Characterisation - Amplitude
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Sand
AI AI
Gas
Shale
Sg = 70 %Sg = 0 %
GR
Shale
Sand
Sg = 70%
Gassmann fluid substitution approximately valid
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Seismic Characterisation - Amplitude
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GR Sg=0%
Sand
Sg=2% Sg=20% Sg=50% Sg=70%
Gas
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Seismic Characterisation – Amplitude
Can AVO help?
17Feng & Bancroft, 2006
Sg=70%Sg=70%
San
d
0
-1
Am
plit
ud
eAngle
0 40Offset (angle)
top reservoir
GR
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Seismic Characterisation Shallow Gas
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Seismic Characterisation - Flat Spot
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Flat Spot visible
GWC
Sg = 60%
Sg = 2%
GWC
‘Flat spot’ visible
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Seismic Characterisation - Flat Spot
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Flat Spot visible
GWC
Sg = 60%
Sg = 2%
GWC
A12-FA Field (producing)
‘Flat spot’ visible No flat Spot visible
Producing field
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Seismic Characterisation - Flat Spot
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Reservoir = 50m
Sg = 60%, Column = 50m
Reservoir = 50m
Sg = 60%, Column = 10m
Reservoir = 10m
Sg = 60%, Column = 50m
Visibility of flat spot dependent on:
Dip of reflectors
Reservoir thickness
Column height
Flat spot indicates reservoir thickness & HC column, not saturation
TVD
ss (
m)
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Pull-down
Seismic Characterisation - Velocity Pull Down
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→ Pull-down indicates (total) HC column
→ Absence pull-down indicates very low saturation
Pull-downPull-down
Seismic data courtesy Spectrum
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Seismic Characterisation Shallow Gas
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Seismic Characterisation - Attenuation
25→ Absence attenuation indicates very low saturation
Attenuation
No attenuation
(& pull-down)
Seismic data courtesy Spectrum
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Seismic Characterisation - Gas Chimney
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Gas chimney indicator for gas
TWT
(ms)
Seismic data courtesy Spectrum
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Shallow fieldsShallow leads
• 8 fields (wells)
• > 150 leads (seismic data)
• Semi-quantitative seismic characterization useful for first order ranking
• AVO analysis ongoing
• Ultimate derisking requires the bit?
SummaryDerisking Shallow Gas as Exploration Target by Seismic Characterisation
27→ Find cost efficient solutions
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Acknowledgements
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• TNO
• Ikon Science
• Petrogas (E. Campbell, K. Borowski)
• EBN B.V. (B. Scheffers, E. Rosendaal)
www.ebn.nl
www.nlog.nl (public seismic & well data)
Opportunities
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Acknowledgements
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• Spectrum, seismic data courtesy
• TNO
• Ikon Science
• Petrogas (E. Campbell, K. Borowski)
• EBN B.V. (B. Scheffers, E. Rosendaal)
Questions to [email protected]