seismic characterisation of shallow gas in the … - underexplored plays... · seismic...
TRANSCRIPT
Seismic Characterisation of
Shallow Gas in The Netherlands
Underexplored Plays Regional Conference, Stavanger 2015
Mijke van den Boogaard & Guido Hoetz (EBN)
Hazard?Deep source?
Opportunity?
Shallow Gas Pays Off!
3
www.offshore-mag.com
2007
Today ~8 bcm gas produced www.dana-petroleum.com
2009
www.hsm.nl
2011
Outline
4
1. Introduction
2. New play rather than hazard
3. Seismic characterisation
4. Summary
Denmark
Geological Setting
5
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
~1
km
~10 km
6
amplitude anomalies
salt domes
Mid-Miocene
Unconformity
Top Chalk
SW NE
Geological Setting
Shallow Gas in Norway
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
Shallow Gas Portfolio
9
Producing
Shallow Gas Production
10
• 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
Shallow Gas: new play rather than drilling hazard
11
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
Seismic Characterisation Shallow Gas
12
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
Seismic Characterisation Shallow Gas
13
VolumesDHI’s
Seismic Characterisation - Amplitude
14
A12-03 B13-04
TWT
(ms)
NW SE
A12 field (producing)
GR GR
Sg = 70%
Sg = 0%
Seismic Characterisation - Amplitude
15
Sand
AI AI
Gas
Shale
Sg = 70 %Sg = 0 %
GR
Shale
Sand
Sg = 70%
Gassmann fluid substitution approximately valid
Seismic Characterisation - Amplitude
16
GR Sg=0%
Sand
Sg=2% Sg=20% Sg=50% Sg=70%
Gas
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
Seismic Characterisation Shallow Gas
19
Seismic Characterisation - Flat Spot
20
Flat Spot visible
GWC
Sg = 60%
Sg = 2%
GWC
‘Flat spot’ visible
Seismic Characterisation - Flat Spot
21
Flat Spot visible
GWC
Sg = 60%
Sg = 2%
GWC
A12-FA Field (producing)
‘Flat spot’ visible No flat Spot visible
Producing field
Seismic Characterisation - Flat Spot
22
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)
Pull-down
Seismic Characterisation - Velocity Pull Down
23
→ Pull-down indicates (total) HC column
→ Absence pull-down indicates very low saturation
Pull-downPull-down
Seismic data courtesy Spectrum
Seismic Characterisation Shallow Gas
24
Seismic Characterisation - Attenuation
25→ Absence attenuation indicates very low saturation
Attenuation
No attenuation
(& pull-down)
Seismic data courtesy Spectrum
Seismic Characterisation - Gas Chimney
26
Gas chimney indicator for gas
TWT
(ms)
Seismic data courtesy Spectrum
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
Acknowledgements
28
• 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
Acknowledgements
29
• Spectrum, seismic data courtesy
• TNO
• Ikon Science
• Petrogas (E. Campbell, K. Borowski)
• EBN B.V. (B. Scheffers, E. Rosendaal)
Questions to [email protected]