The nature of the basement to the Cooper Basin region, South Australia

Magnetotelluric monitoring of hydraulic fracture stimulation at the Habanero Enhanced Geothermal System, Cooper Basin, South Australia

“…The intermediate resistivity structure (R1) can be correlated to consolidated sandstones, siltstones and shales of the Cooper basin (natural gas and petroleum reservoir rocks). The high resistivity structure at depth of about 3.5 km (R2) is interpreted as the intrusive granodiorite (granite) of the Big Lake Suite with low porosity and permeability (Holl and Barton 2015, Meixner, et al 2000. A decrease in resistivity due to simulation of Habanero-4 well at 4 km depth is expected to occur at a period greater than 10 s. A typical resistivity phase curve for pre-and post-injection for site 09 which is located 870 m NE of Habanero-4 is shown in Figure 5 (refer to Figure 1 for location of site 09).…”

“…The main reasons for observing small changes in resistivity at Habanero EGS are the screening effect of the conductive sedimentary basin in the area (about 3.6 km thick) and the presence of pre-existing saline fluids with resistivity of 0.1 Ωm (salinity of 16.1 g/L at 240°C) in the natural fractures in the EGS reservoirs (Hogarth, et al 2013, Holl and Barton 2015, Meixner, et al 2014, Yanagisawa, et al 2011. Furthermore, the stimulated reservoir at Habanero is a granitic basement with low permeability while the targeted reservoir at Paralana is a neo-Proterozoic meta-sedimentary formation (Holl and Barton 2015, Llanos, et al 2015, Meixner, et al 2000, Peacock, et al 2013). The time-lapse continuous monitoring MT study at Habanero highlights the need for favourable geological settings to achieve significant change in resistivity in EGS reservoirs.…”

Geophysical anomalies and quartz deformation of the Warburton West structure, central Australia

“…for a 2.9 gr/cm 3 set in a 2.8 gr/cm 3 background, as for the Warburton East model (Meixner, 1999(Meixner, , 2000, no distinct coincident gravity anomaly is observed in the north-south section. The role of deep crustal fracturing, suggested by the seismic tomography…”

“…Extensive sericite alteration of feldspar suggests hydrothermal alteration to a depth of ~500 m below the unconformity which overlies the Warburton East Basin (Boucher, 2001;Middleton et al, 2013Middleton et al, , 2014. East body which ranges up to 0.037 SI (Meixner 1999(Meixner , 2000. There is, however, no distinct gravity anomaly that coincides with the magnetic high.…”

“…The Warburton East Basin is associated with major geophysical anomalies which include a positive magnetic high of near-200 nT centred on a ~25 km-wide magnetic low of <100 nT which has been modelled in terms of a magmatic body deeper than 6 km (Meixner et al, 1999(Meixner et al, , 2000. A distinct seismic tomographic low velocity anomaly may reflect its thick (9.5 km) sedimentary section, high temperatures and possible deep fracturing to mid-crustal depth Kennett, 2010, 2012;Glikson et al, 2013).…”