Data Collection

Collection of new heat flow data

Figure 1:
Existing (circles) and new
(stars) heat flow data for Australia

Figure 2:
Temperature logging system

Figure 3:
Thermal conductivity metre

Figure 4:
Thermal conductivity samples

One of the primary activities of the Geothermal Energy Project in Geoscience Australia is the collection of new heat flow data. Heat flow is an important parameter needed to predict temperatures at 3 - 5 kilometre depth in the crust, the depth to which companies often need to drill to produce electricity from geothermal energy.

Measuring heat flow is a two-step process which requires both field-based and laboratory-based measurements. Wireline logging equipment is used to measure the temperature down a borehole, and a thermal conductivity meter is used to measure the thermal conductivity of rock samples collected from the same borehole. The temperature measurements in conjunction with measured conductivity will enable Geoscience Australia to estimate the heat flow at each site.

The Geothermal Energy Project has acquired the field and laboratory equipment required to measure heat flow. It began thermal logging of boreholes across Australia in late 2008; the locations of new measurements are shown as stars in Figure 1. In late 2009, the thermal conductivity meter became operational, allowing the project to begin thermal conductivity measurements of samples collected from logged boreholes.

Temperature logging

The Geothermal Energy project measures temperature down existing boreholes located throughout Australia. The project's temperature logging system (Figure 2) can measure temperature up to 70°C and down to 1.8 kilometres. The probe also measures natural gamma radiation emitted from rocks surrounding the borehole.

Temperature is measured every 20cm to a precision of 0.001°C.

The system is trailer mounted and runs on a small generator.

Thermal conductivity measurement

Thermal conductivity is a measure of how well a rock transmits heat. Rocks with low thermal conductivity are good insulators meaning that they are good at trapping heat in the earth.

Thermal conductivity measurements are carried out on an Anter UNITHERM™ guarded heat flow thermal conductivity meter (Figure 3). The instrument can measure thermal conductivity at between 0°C and 300°C, which is important because thermal conductivity varies with temperature. It takes discs that are 2.5cm wide and about 2cm thick (Figure 4).

Topic contact: Last updated: April 2, 2013