Science & Technology: "Heat Needle" Helps Produce Surface Heat Flow Map over Entire Geothermal Prospect

Heat flow maps at 'prospect' scale (LinkedIn)

by Graeme Beardsmore (GRC Member), Technical Director, Hot Dry Rocks PL, Victoria, Australia

What if we could produce a surface heat flow map over an entire geothermal prospect for less than the cost of a single heat flow well? After 10 years of R&D, Hot Dry Rocks PL has demonstrated a tool that can do just that. We call it the Heat Needle.

The system works like this. We drill a one meter long rod into the ground with an off-the-shelf electric drill, and insert a set of highly sensitive and accurate thermal sensors. These sensors passively record the temperature in the top meter of the ground several times each hour for several months. When processed in the frequency domain, these records of ground temperature tell us the thermal diffusivity of the ground to a precision of ~±1%. We also correlate our site-specific records of surface temperature against more diffuse but long-term satellite-derived records of surface temperature. That lets us extend our own surface temperature record many years into the past.

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