Exploring the sub-salt play in the frontier Amadeus Basin – Insights from potential field data analysis

T Debacker, K Connors, J Lee, S Watters, J Clifford, P Plummer and S Menpes

EXPLORING THE SUB-SALT PLAY IN THE FRONTIER AMADEUS BASIN – INSIGHTS FROM POTENTIAL FIELD

DATA ANALYSIS Timothy Debacker1, Karen Connors1, Jia-Urnn Lee1, Sandy

Watters2, Jenni Clifford2, Phil Plummer2 and Sandra Menpes2

1 FROGTECH 2 Santos Ltd Email: tdebacker@frogtech.com.au

AGES, 2016 Alice Springs

Thanks to C. Pietruchia, C. Jorand, Z. Shi, A. Kroll, M. den Hartog (FROGTECH), E. Hissey and W. Aspinal (Santos) and exploration team of Central Petroleum

© Santos Ltd

Introduction: Exploring the Sub-salt Play in the Southern Amadeus Basin

Sub-salt Play • Primary exploration target • Neoproterozoic lower Gillen-

Heavitree petroleum system • Gas flows from Magee-1 (1992)

and Mt Kitty-1 (2014) have proven the sub-salt play

2013 AMSAN 2D Seismic Survey • First regional framework 2D

seismic • 1586 line km over an area totalling

43,000 sq km • Line length up to 387km

Objectives • Provide regional structural and

stratigraphic framework • Link isolated 2D grids • Identify key leads for follow up

Introduction: New Sub-salt Leads Identified • Two significant sub-salt leads

identified (Dukas shown here) • Regional framework seismic

grid - higher spatial density magnetic and gravity surveys useful for interpolating trends away from seismic and well control.

• Santos contracted FROGTECH to update the SEEBASE™ Depth-to-Basement Model of the Amadeus Basin

2004 SEEBASE™

Introduction: SEEBASE™ update

2005 SEEBASE™

FROGTECH update for Santos of 2004 and 2005 SEEBASE™ of Amadeus Basin, calibrated with newly acquired seismic data

2014-2015 SEEBASE™

Basin Stratigraphy • Central and eastern parts dominated by NW-SE trends,

with exceptions • More random trends in western parts, above Gillespie

Craton. • Central zone with Neoproterozoic units at surface with a

broadly anticlinal geometry, but extensively brecciated in many areas.

F Anticline

Basement thrust fault

Fault M Syncline

Structure

Cambrian Unconformity Petermann Unconformity

Crystalline Basement

1

2

3

4

Centralian Extension I

Salt-bearing unit: Gillen Member of the Bitter Springs Formation

Petermann Orogeny

Centralian Extension II

SW NE

Potential field data Gravity data:

• ~E-W-trending long-wavelength positive and negative gravity anomalies

• ~NW-SE-trending, elongate short-wavelength positive gravity anomalies (central and east)

• Variable moderate to short-wavelength gravity trends in west

BG HP300 km

RTP CMY ternary

Magnetic data:

• Shallow magnetic (and “non-magnetic”) basement surrounding Amadeus Basin

• ~NE-SW-trending moderate to long-wavelength anomalies below central and eastern Amadeus Basin

• ~NW-SE-trending, elongate short-wavelength magnetic anomalies (central and east)

• Variable moderate to short-wavelength magnetic trends in west

BG HP200 km

RTP CMY ternary

Potential field data and basement terranes • Cratonic basement below western

Amadeus Basin

• Link with Albany-Fraser Orogen for basement below central and eastern Amadeus Basin (cf. Betts et al., 2011)

Gillespie

Gillespie

Musgrave Province / Petermann Orogeny

• Predominantly detached Petermann Orogeny deformation style, facilitated by Bitter Springs Formation salts

• Local basement-involved Petermann Orogeny deformation style

• Deformation asymmetry decreases N-ward, away from Musgraves

• Seismic wash-out zones flanked by upturned sediments, interpreted as (brecciated) salt mobilisation zones

Deformation style and link with gravity data

amsan 13B-04

Detached Petermann Orogeny faults

Reverse basement fault, possibly inverted Centralian normal fault

Seismic wash-out zones correspond to local positive gravity anomalies and are interpreted to be zones of intensely brecciated carbonate and anhydrite as a result of salt mobilisation

Metasedimentary basement (?) affected by Petermann Orogeny reverse faults

Crystalline basement

S N

Petermann Unconformity

Delamerian Unconformity

3s

BG HP300 km

Deformation style and link with gravity data

High-Pass 20 km

High-Pass 50 km

Wash-out zone Wash-

out zone

• Elongate ~NW-SE-trending short-wavelength positive gravity anomalies are linked to upturned carbonates of Bitter Springs Formation

• Edges of seismic wash-out zones correspond to elongate short-wavelength positive gravity anomalies

• In general seismic wash-out zones correspond to positive gravity anomalies

3s

Deformation style and link with gravity data • High-density intrabasinal sources contributing to central positive gravity anomaly:

• (1) coherent sedimentary packages containing dolomite and limestone

• (2) highly disrupted zones that show up as wash-out zones on seismic.

BG HP200 km

1

1

1

1 1

1

2

2

2

2 2

BG HP300 km

Deformation style and link with gravity data • Basement in Mereenie area shallower than

expected from position relative to regional negative gravity anomaly

Hermannsberg section (Warren & Shaw, 1995) ~ - 11km

N S

NE SW

Neoproterozoic deformed during

Petermann Orogeny

Basement-involved Alice Springs Orogeny

deformation

Interpreted Centralian fault

Basement

Petermann Unconformity

Mereenie p81-ge08r1

3s

• Basement-involved Alice Springs Orogeny (II and III) deformation style

• Strong basement control on compressional deformation geometry in central and northern part of Amadeus Basin

Deformation style and link with gravity data

F Anticline M Syncline

Ordovician extension lineament Centralian extension lineament Albany-Fraser I lineament

Surface geology Alice Springs Event Post-Petermann Ord-Sil Cambrian post-Petermann Petermann Event Boord-Inindia

NE SW

Neoproterozoic deformed during

Petermann Orogeny

Basement-involved Alice Springs Orogeny

deformation

Interpreted Centralian fault

Basement

Petermann Unconformity

Mereenie p81-ge08r1

3s

• Three regional gravity models

• East line to investigate contribution of high-density Neoproterozoic sediments to central positive gravity anomaly

• Gravity models constrained by seismic data, wells, cross-sections, surface geology and density values from wells .

Gravity Modelling BG HP300 km

T1 T2

T3

Basement

X

Line amsan13b-04

Petermann Unconformity

(blue)

Delamerian Unconformity (yellow)

X X X

X X X

• Eastern gravity model shows significant contribution of high-density Neoproterozoic sediments to central positive gravity anomaly

Gravity Modelling Devonian-Carboniferous sequence

Basement (Musgrave or Warumpi equivalent)

Basement (Arunta West Terrane)

Neoproterozoic sequence

Cambrian sequence

Silurian sequence

Intensively deformed carbonates and evaporites related to salt mobilisation

Lower crust

Legend

Basement (Musgraves S, Warumpi N)

Fault zone

• Central gravity model focusses on source of long-wavelength gravity anomalies

Gravity Modelling

2.69 – Upper Crust

2.75 – Lower Crust

2.82 2.76 2.75

2.85 2.90

3.32 - Mantle

2.84

2.90 2.99

2.97

2.91

2.74

2.70

2.84 2.74

2.64

2.74

2.96

2.69 2.75 2.70 2.67

2.55 2.69 2.75

2.74 2.64

2.67 2.79

2.70 2.63

Petermann Nappe Complex

High-density basin units beneath thrust nappe

Musgrave Province

Warumpi Arunta West

Central Australian

Suture

Man

n Fa

ult

Tikelmungulda Seismic Province

metasediments

Basement (Musgrave equivalent) Basement (Arunta and Warumpi terranes)

Syn-Petermann sequence (”Winnall Beds”)

Deformed carbonates and evaporites (basal Bitter Springs Fm.) and Dean/Heavitree Quartzite

Lower crust

Legend

Bitter Springs Formation Boord Formation / Inindia Beds

BG HP100 km

Potential field data interpretation BG HP300 km

RTP CMY ternary

Gravity data:

• Short-wavelength anomalies caused by intrabasinal sources (upturned carbonates, salt mobilization residuals)

• ~E-W-trending long-wavelength positive and negative gravity anomalies are result of shallow high-density basin units, changes in basement depth, changes in Moho depth, and crustal density variations

Magnetic data:

• ~NE-SW-trending moderate to long-wavelength anomalies reflecting compositional variations related to Albany Fraser Orogen (cf. Betts et al., 2011)

• Illustrate changes in depth of magnetic basement

• Top of magnetic basement usually deeper than top economic basement

Potential field data interpretation

RTP CMY ternary Magnetic data:

• Top of magnetic basement usually deeper than top economic basement

Petermann Nappe Complex

Musgraves

Conclusions

New SEEBASE of Amadeus basin based on Santos seismic new NTGS potential field data and open file data from GSWA

2016 Exploration Program

2016 2D Seismic Survey • 1300 km 2D seismic infill program • Designed to mature leads identified from

the 2013 seismic survey and the 2014–2015 SEEBASE™ depth-to-basement map to drillable prospect status

• Two rounds of acquisition – Round 1 lines are firm

• In-field processing and preliminary interpretation to determine which Round 2 lines will be acquired

Legend

2013 Seismic Acquisition

2016 Seismic Round 1

2016 Seismic Round 2

Dukas

Background image Digital Elevation Model

Background image 2014–2015 SEEBASE™ depth-to-basement model