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

Santos Ltd (Santos) entered into the southern Amadeus Basin (Figure 1) via a partnership with Central Petroleum Ltd in 2012 to explore the sub-salt and intra-salt plays of the Neoproterozoic lower Gillen-Heavitree Petroleum System. A central basin high and focus for regional hydrocarbon migration was postulated to have formed as a result of deformation and loading of the basin to the south (580–530 Ma Petermann Orogeny), and later deformation and loading to the north (450–300 Ma Alice Springs Orogeny). The primary exploration objective was the Heavitree Quartzite, a fluvio-marine sandstone that had flowed gas from Magee-1 (drilled 1992), the only well to test the Neoproterozoic sub-salt play in this frontier basin at that time. Subsequently, a second test of the play, the Southern Amadeus Joint Venture’s Mt Kitty-1 well, flowed gas from fractured granitic basement. This test confirmed the existence of an extensive sub-salt petroleum system as well as the excellent sealing capacity of the Neoproterozoic evaporites. Gas flows from both wells recorded helium contents of ca 6–9% in addition to hydrocarbon and inert gases. In 2013 Santos acquired over 1500 km of regional 2D seismic across the Southern Amadeus Joint Venture (SAJV) permits (Figure 1). This survey was the first regional seismic dataset acquired over the southern Amadeus Basin; it resulted in the identification of two significant sub-salt structures, named Dukas and Mahler. The Dukas lead, located north of Murphy-1, comprises a large and broad basement roll-over mapped on three seismic lines (Figure 2). Post-salt reflections are clearly imaged, but data quality is highly variable where salt mobilisation has occurred with basement locally difficult to image. Infill seismic is to be acquired in 2016 to advance both the Dukas and Mahler leads to drillable prospects. In areas where seismic coverage is sparse (as it is across much of the southern Amadeus Basin) or of poor quality, higher spatial density magnetic and gravity surveys can be used to interpolate trends between seismic and well control. In 2014, Santos contracted FROGTECH to update the SEEBASETM Depth-to-Basement Model of the Amadeus Basin (Munroe et al 2004, FROGTECH 2005). The model was calibrated with the newly acquired regional seismic data to provide a high-resolution depth-to-basement model for the Amadeus Basin and to place the primary sub-salt