Magnetotelluric survey (time series) of an enhanced geothermal system fluid injection at 3.6-km depth near Paralana, South Australia, March 2010

Brief description

This record was harvested by RDA at 2024-02-14T09:51:51.483+11:00 from NCI's Data Catalogue where it was last modified at 2019-05-02T16:20:44.

Full description

Monitoring fluid flow in enhanced geothermal systems (EGS) is vital to reservoir growth and production. Geothermal fluids are innately conductive due to high temperature and pressure and dissolved enhanced ion concentration. This can be exploited by geophysical measurements sensitive to subsurface conductivity changes at several hundreds of meters to a few kilometres depth, such as magnetotellurics (MT).

In July 2011, an EGS fluid injection at 3.6-km depth near Paralana, South Australia, was monitored by comparing repeated MT surveys before and after hydraulic stimulation. Prior to injection, four different base surveys were collected due to varying data quality and for an estimation of repeatability between measurements. Note that not all stations were repeated four times, but all were repeated at least two times. The first survey was collected in March 2010 where instruments were left out for an average of 18 h. A total of 34 stations that did not record quality data were repeated during a second survey in May 2010, when instruments were deployed for an average of 30 h. Unfortunately, the EPIC pipeline that runs parallel to the north–south line was performing its annual corrosion test by sending a 3-s electric square wave every 12 s, saturating the MT data in the period range of 1–12 s and harmonics of 12 s. The entire survey was repeated in March 2011, when the pipeline was again emitting a similar periodic signal, but reduced in amplitude. Instruments were deployed for an average of 40 h to increase estimation of Z.

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