Abstract: An apparatus for performing a thermal response test to determine thermo-physical properties of a geothermal heat exchange resource. The apparatus includes a geothermal heat exchanger adapted to circulate a fluid through a loop in a sample borehole in the geothermal heat exchange resource and a variable speed pumping system capable of time-dynamic control of a fluid flow rate of the fluid. A multi-stage heating system is capable of applying a series of time-dynamic heat pulses to the fluid. The apparatus further includes a fluid temperature sensor and one or more fluid pressure, fluid density and/or fluid flow rate sensors, the sensors measuring data on the properties of the fluid that are predictive of the thermo-physical properties of the geothermal heat exchange resource.