Exploration of a sub-salt play in the Southern Amadeus Basin, Central Australia – searching for big gas in Proterozoic reservoirs D.R. Johns, S. A. Menpes, P. Walshe and F. Bache Santos Ltd., 60 F l inders Street, Adelaide 5000, South Australia, Australia SEAPEX 2017
Proterozoic Amadeus Basin, Northern Territory, Australia Amadeus Basin – Neoproterozoic to Palaeozoic basin part of Centralian Superbasin SEEBASE TM 2014- 2015 SEEBASE™ Proterozoic – Palaeozoic sedimentary fill with several proven petroleum systems • Targets are TCF-sized gas resource in conventional structures under Proterozoic evaporite seals • Seismic program well advanced with drilling planned for 2019 • Seapex 2017
Amadeus Basin; Wells, Seismic, and Infrastructure Northern Amadeus Basin; Phanerozoic petroleum system, Mereenie and Palm Valley fields Southern Amadeus Basin; Proterozoic petroleum system, under explored. 50 km Seapex 2017
Basin shape Amadeus Basin; Conceptual Play Cross Section Proterozoic section in the south, Palaeozoic section in the north NORTH Mereenie SOUTH Petermann unconformity Palm Valley Dingo Surprise ERODED ARUNTA MUSGRAVE BLOCK PROVINCE UPLIFT R R R S R R S Dukas S S S S S S • Thick, deformed Bitter Springs • Thick, strongly folded, evaporite sequence Cambrian to Devonian series above the Petermann • Thin, slightly deformed, Cambrian to unconformity: Devonian series above the Petermann unconformity: • Strong Alice Springs deformation • Some minor Alice Springs deformation Seapex 2017
Structural framework: summary Amadeus Basin; Tectonic Elements Three tectonic trends influenced basin development 3 2 Seapex 2017
Petroleum systems and play intervals Southern Amadeus Basin Key Wells Wells in the south have penetrated a thick Proterozoic evaporite sequence and two wells Magee-1 and Mt Kitty-1 have tested gas from below the evaporites Seapex 2017
Neoproterozoic Sub-salt play Gas flows from Magee-1 (1992) and Mt Kitty-1 (2014) have proven the sub-salt petroleum system Mt Kitty-1 OHT Magee-1 Magee-1 Mt Kitty-1 OHT 50 km 2 wells have tested the sub-salt play, both flowed hydrocarbons proven petroleum system Highly competent regional evaporite seal Material Helium, elemental H, valuable by-products Seapex 2017
Heavitree Play Interval (1) - Outcrops Heavitree Sandstone; Regional context The Heavitree/Dean Quartzite ranges from 200m to 1000m thick North and South of the Amadeus Basin. Likely deposited as an extensive sheet sandstone in the Centralian Superbasin Ellery Creek Magee-1 Heavitree 6.3 m Mt Kitty-1 Basement (Heavitree absent) 50 km Basement thrust S S R Seapex 2017
Amadeus Basin Exploration Program 1300 km planned 2D seismic program to mature opportunities for drilling in 2019 2013 2D Seismic Survey • First regional 2D seismic • 1586 line km over 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 2016/7 2D Seismic Survey • 1300km of seismic infill ; 932km acquired, remainder later in year • Acquisition and processing parameters modified • Longer offsets, higher sampling, longer sweep length, infield and fast-track processing Seapex 2017
Southern Amadeus Basin; East-West Regional Strike Line Section (386km) demonstrates thinning and onlap of Neoproterozoic section to East Magee-1 ms Petermann Unconformity E W Gillen Salt Near Top Heavitree Mesoproterozoic pre-Amadeus unit 10 km Salt disturbed zones Gradual shallowing of interpreted basement/near top Heavitree Fm; onlap and thinning of • Neoproterozoic section towards the SE basin margin Significant seismic wash-out zones in areas of thick salt and/or intense halotectonics • Imaging of very thick Mesoproterozoic pre-Amadeus unit – potential proto-Amadeus rift succession? • Seapex 2017
Southern Amadeus Basin; Lead B updip of Magee-1 Lead B - updip of Magee-1 (1991), wet gas flow from sub-salt play ms NW Magee-1 Chandler Salt SE Gillen Salt Lead B Near Top Heavitree Mesoproterozoic pre-Amadeus unit 10 km AMSAN13B-06 Thinning of Neoproterozoic unit onto the SE basin margin • Mesoproterozoic pre-Amadeus unit is better imaged where basement is shallow and Gillen salt is thin and • undeformed Seapex 2017
Southern Amadeus Basin; Sub-salt Play-Trap Central arch a long term regional migration focus, speculative rift precursor basin remnants in western sector, stress regime more favourable ms Murphy-1 S Detached Petermann Orogeny faults Petermann Unconformity Gillen Salt Central Near Top Heavitree High Lead (Lead A) Meta(?)sedimentary precursor basin section (?) affected by Petermann Orogeny reverse faults 10 km Central High Lead part of regional sub-salt basement high and likely migration focus Difference in deformation style between south and north • South Detached thrust faults related to early Petermann Orogeny & relatively undeformed Petermann U/C • North Phanerozoic deformation as a result of Devonian Alice Springs Orogeny, does not extend south of central high Seapex 2017
Southern Amadeus Basin Sub-salt Play - SEAL Evaporites – Highly competent seal traps H, He and hydrocarbons and protects from tectonic breaching East Siberia Thick Cambrian evaporite seal has taken • up tectonic deformation, protecting underlying hydrocarbon accumulations from tectonic breaching Effective top seal traps He (0.2% in • W E Yurubcheno-Tokhomskoye Field) Multi-TCF gas fields and billion bbl oil • fields Amadeus Thick Neoproterozoic evaporite seal has • taken up tectonic deformation, protecting underlying hydrocarbon accumulations from tectonic breaching Effective top seal traps H and He (Mt • Kitty and Magee accumulations) Multi-TCF gas opportunities • Seapex 2017
Southern Amadeus Basin; Sub-salt Play - RESERVOIR Gas flows from natural fractures in granite and pre-salt carbonates Image Log Mt Kitty Flow Tests First significant gas below evaporite succession from fractured Lower Gillen dolomite Basement Fractures Top Basement #1 #2 Flow test #2 Petermann Unc 10m #3 #4 3 km Flow test #2 Seapex 2017
Gillen Play Interval (2 and 3) Southern Amadeus Basin; Raft Play Rafts are made of (probable) Upper Gillen dolomite that sank into the Gillen halite in the core of anticlines Petermann unconformity SW NE Erldunda-1 Upper Bitter Springs Upper Gillen 13b08 S S R Seapex 2017
Seismic Reprocessing – AMSAN 13b-04 Enhance imaging of sub-salt reflector and supra-salt section Original Processing - 2013 Reprocessing - 2017
Gillen Play Interval (2 and 3) Southern Amadeus Raft Play; South Oman Analogue Rafts within salt section of the Southern Amadeus Basin compare favourably with Dolomite stringers in Salt from South Oman Seapex 2017
Summary and Conclusions + Hydrocarbons have been generated and trapped below sealing Neoproterozoic evaporites in the Southern Amadeus Basin + Large structural features are present that are currently being defined by a seismic acquisition program currently underway + The Heavitree sandstone is the primary target; regional evidence points to a fluvio-marine sheet sand onlapping and to the east and thickening into the basin to the west + Secondary targets are Gillen dolomites present as rafts within the evaporites. There are analogies with the South Oman late Phanerozoic to Palaeozoic dolomite ‘stringer’ play + Seismic acquisition will be resumed in the 3 rd quarter 2017 with the intention of further defining targets for drilling in 2019 Seapex 2017
Acknowledgements + The authors wish to thank current and past members of the Southern Amadeus Exploration team, Santos Regional Exploration team and Santos’ Operation Geophysics team + Santos also acknowledges and thanks the exploration team of our partner, Central Petroleum. + The authors wish to thank Santos for permission to present this presentation Seapex 2017
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