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 mijke.boogaard-van-den@ebn.nl