Post on 15-Oct-2021
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