GNS Science

Facies Distribution and Impact on Petroleum

Migration in the Canterbury Basin, New Zealand

Tusar R. Sahoo1, Karsten F. Kroeger1, Glenn Thrasher1, Stuart Munday2,

Hugh Mingard3, Nick Cozens2 and Matthew Hill1

1 GNS Science, Lower Hutt, New Zealand 2 New Zealand Oil & Gas, Wellington, New Zealand 3 Mingard Geoscience Ltd, Christchurch, New Zealand

GNS Science

Seismic data coverage and drilled wells

2D/3D Seismic data:

Reprocessed seismic lines and acquired

seismic lines since 2006 are of reasonable

quality for facies interpretation.

Waka3D is of very good data quality for

facies interpretation.

Sub-commercial gas-condensate discovery:

Clipper-1 and Galleon-1

Oil & Gas shows:

Cutter-1 and Caravel-1

Study area

Caravel-1

Waka 3D

GNS Science

Objectives of this study

• Producing an updated series of paleogeographic maps

showing source, reservoir and seal rock distribution

• Understanding key risks associated with petroleum system

elements using a 2D basin modelling

GNS Science

Overview of talk

• Stratigraphic framework

• Seismic facies characterisation

• Paleogeographic maps

• 2D petroleum system modelling

GNS Science

Stratigraphic framework

Clipper-1

Rifting started in mid Cretaceous

(~ 105 Ma; Davy, 2014)

GNS Science

Early Oligocene erosion Isopach map between Paleocene (P10)

and Eocene (P50)

a

top Oligocene ?

top Eocene

channels

channels

channels

Coherency map at top Eocene

b

c Waka 3D

Waka 3D

Clipper-1

GNS Science

Seismic facies characterisation

Galleon-1

followed approach by

Mitchum and Vail (1977)

GNS Science

Seismic facies characterisation

Facies Seismic reflection character

Amplitude Lateral continuity Geometry

Alluvial fans Low-moderate Discontinuous-low Chaotic, steeply dipping, wedge like

Fluvial facies Variable Discontinuous-low Chaotic-sub-parallel

Coastal sandstone & siltstone

Moderate Moderate-continuous Parallel to sub-parallel and part of sigmoidal deltaic unit

Coastal coal measures High Moderate-continuous Parallel to sub-parallel and part of sigmoidal deltaic unit

Shoreface sandstone & siltstone

variable Low on dip direction Parallel-slightly divergent

Shelfal sandstone & siltstone

Moderate-high Moderate-high Parallel, distal part of sigmoidal deltaic unit

Shelfal mudstone Low Low Parallel

Bathyal mudstone Low-moderate Variable Parallel

Co

asta

l M

arin

e

Terr

est

rial

GNS Science

Seismic facies characterisation

b

c

b c

GNS Science

Paleogeographic maps

Syn-rift levels

coal measures

of Clipper Fm.

coal measures

of Clipper Fm.

GNS Science

Paleogeographic maps

Post-rift levels

coal measures of

Pukeiwitahi Fm.

GNS Science

Paleogeographic maps

Post-rift levels

GNS Science

mid Cretaceous; 85 Ma Basement

top Paleocene

top Cretaceous

top Miocene

2D petroleum system model

Tartan Fm.

• Source rock parameters and kinetics are

taken from Sykes and Funnell (2002)

• Average heat flow: ~ 62 mW/m2

Dep

th (

m)

1000

2000

3000

4000

5000

6000

7000

8000

Clipper-1

20 km

Clipper-1

Igneous intrusion

GNS Science

Model calibration at Clipper-1

Vitrinite reflectance being

supressed by their perhydrous

nature (Newman et al., 2000;

Sykes & Funnell, 2002)

Gibbons & Herridge (1984)

VIRF data, Newman et al., (2000)

GNS Science

20 km

Present day maturity

Igneous intrusion

Basement top mid Cretaceous

top Cretaceous

top Paleocene

Maturity (%Ro) Sweeney & Burnham (1990)

Clipper-1 Pseudo well-1 Pseudo well-2

Tartan Formation

Dep

th (

km

)

1

2

3

4

5

6

7

8

Early mature

GNS Science

Cumulative expelled petroleum at 1D locations

Clipper-1

Pseudo well-1

Pseudo well-2

GNS Science

2D migration model

20 km Basement

top mid Cretaceous

top Cretaceous

Clipper-1

Tartan Formation

Dep

th (

km

)

1

2

3

4

5

6

oil and gas

accumulation

Hydrocarbon (gas)

accumulation

Igneous intrusion

75 Ma

GNS Science

Summary

Source rocks:

• Mid Cretaceous coaly source rocks (Clipper Formation) are widely distributed and are

considered to be the primary source rock in the basin, as they are sufficiently mature to

expel hydrocarbon.

• Late Cretaceous coaly source rocks (Pukeiwitahi Formation) are restricted to the

southwestern part of the basin and may have generated hydrocarbon beneath the

prograding Neogene foresets.

Reservoir rocks:

• In general, reservoir quality in the fluvial and coastal facies may be limited, and is likely

better in the shoreface–shelfal facies.

Seal rocks: • Shelfal mudstones are widely distributed in the Late Cretaceous and in the Paleocene

section and have the potential to act as a seal rock.

GNS Science

Key risks:

• Early expulsion from the primary source rock (mid Cretaceous) and associated risk related

to the requirement of early seal development to preserve accumulated volumes.

• Heterogeneity in potential reservoir rocks.

• Limited maturity and distribution of Late Cretaceous source rocks.

Accumulation:

• Most of the predicted accumulations along the modelled section contain gas because early

accumulated oil has been replaced by the later expelled gas.

Summary

GNS Science

This work was undertaken as part of the Petroleum Basins Research Programme with direct

Crown funding from the New Zealand Government (Ministry of Business, Innovation and

Employment). Part of the seismic interpretation, seismic facies mapping and

paleogeographic mapping were funded by New Zealand Oil & Gas (NZOG) and Beach

Energy Limited. We would like to thank NZOG and Beach Energy Limited for their support

and permission to publish this work. We would like to thank Paradigm and Schlumberger for

providing access to SeisEarth and PetroMod software respectively.

Acknowledgements:

Thank you for your attention.